Studies in the thiophenol mediated substitution and reductive dehalogenation of 3 bromoacetylcoumarins
- Authors: Magwenzi, Faith N
- Date: 2017
- Subjects: 3-bromoacetylcoumarins , Coumarins , Halogens -- Decontamination , Thiols , Plasmodium falciparum , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/45769 , vital:25546
- Description: A previous study conducted by our group identified indolyl-3-ethanone-a-thioethers (2.1a and 2.1b) as non-toxic, nanomolar, in vitro inhibitors of Plasmodium falciparum. Since the coumarin scaffold is associated with numerous biologically active compounds including antiprotozoal, anti-viral, anti-bacterial, and anti-inflammatory agents we were prompted to investigate coumaryl-3-ethanone-a-thioethers (2.1c) inspired by the activity of 2.1a and 2.1b against P. falciparum. We proposed a three-step synthesis of our target compounds 2.1c. The first step involved the Knoevenagel synthesis of 3-acetyl coumarins (2.3.1a - e) followed by a selective a-bromination to yield 3-bromoacetyl coumarin (2.2a). The final proposed step involved the nucleophilic displacement of the bromine by appropriately substituted thiophenols in either the presence or absence of base (K2CO3). Our initial findings revealed an unexpected major reductive dehalogenation of 2.2a into 2.3.1a. Further investigation revealed a close relationship between the electron withdrawing or donating nature of the thiophenol substituents and the relative formation of nucleophilic substitution or reductive dehalogenation products. Desired thioether products were obtained in higher yields when thiophenol was substituted with electron donating groups i.e. more nucleophilic thiophenols, while conversely, electron withdrawing substituents (i.e. lowered nucleophilicity) resulted in an increase of reductive dehalogenation. Furthermore, these results were consistent when experiments were conducted using either 2 or 1.2 equivalents of thiophenols which was an important observation in the context of two previous studies, by Oki et. al. and Israel et. al. Oki proposed that dehalogenation of a-chloro carbonyls occurs via sequential nucleophilic displacement of a-thioethers, while the study of Israel concluded that the dehalogenation of a-iodo carbonyls occurred in a single discreet step. Finally, in an effort to enhance nucleophilic substitution through the addition of K2CO3, we observed a Robinson annulation resulting in previously undescribed C-8 thiophenol functionalised dibenzo[b,d]pyran-6-ones (3.4a - e). In the introduction to this thesis, we briefly summarise the utility of coumarins in medicinal chemistry and related fields. Chapter two describes the rationalisation of our original research question and a retrosynthetic analysis of our desired compounds, followed by an initial description of the unexpected reductive dehalogenation. Chapter 3, begins with a brief review of reductive dehalogenation of a-halocarbonyls, and is followed by an analysis and discussion of our results in the context of the studies by Israel et. al. and Oki et. al.
- Full Text:
- Date Issued: 2017
- Authors: Magwenzi, Faith N
- Date: 2017
- Subjects: 3-bromoacetylcoumarins , Coumarins , Halogens -- Decontamination , Thiols , Plasmodium falciparum , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/45769 , vital:25546
- Description: A previous study conducted by our group identified indolyl-3-ethanone-a-thioethers (2.1a and 2.1b) as non-toxic, nanomolar, in vitro inhibitors of Plasmodium falciparum. Since the coumarin scaffold is associated with numerous biologically active compounds including antiprotozoal, anti-viral, anti-bacterial, and anti-inflammatory agents we were prompted to investigate coumaryl-3-ethanone-a-thioethers (2.1c) inspired by the activity of 2.1a and 2.1b against P. falciparum. We proposed a three-step synthesis of our target compounds 2.1c. The first step involved the Knoevenagel synthesis of 3-acetyl coumarins (2.3.1a - e) followed by a selective a-bromination to yield 3-bromoacetyl coumarin (2.2a). The final proposed step involved the nucleophilic displacement of the bromine by appropriately substituted thiophenols in either the presence or absence of base (K2CO3). Our initial findings revealed an unexpected major reductive dehalogenation of 2.2a into 2.3.1a. Further investigation revealed a close relationship between the electron withdrawing or donating nature of the thiophenol substituents and the relative formation of nucleophilic substitution or reductive dehalogenation products. Desired thioether products were obtained in higher yields when thiophenol was substituted with electron donating groups i.e. more nucleophilic thiophenols, while conversely, electron withdrawing substituents (i.e. lowered nucleophilicity) resulted in an increase of reductive dehalogenation. Furthermore, these results were consistent when experiments were conducted using either 2 or 1.2 equivalents of thiophenols which was an important observation in the context of two previous studies, by Oki et. al. and Israel et. al. Oki proposed that dehalogenation of a-chloro carbonyls occurs via sequential nucleophilic displacement of a-thioethers, while the study of Israel concluded that the dehalogenation of a-iodo carbonyls occurred in a single discreet step. Finally, in an effort to enhance nucleophilic substitution through the addition of K2CO3, we observed a Robinson annulation resulting in previously undescribed C-8 thiophenol functionalised dibenzo[b,d]pyran-6-ones (3.4a - e). In the introduction to this thesis, we briefly summarise the utility of coumarins in medicinal chemistry and related fields. Chapter two describes the rationalisation of our original research question and a retrosynthetic analysis of our desired compounds, followed by an initial description of the unexpected reductive dehalogenation. Chapter 3, begins with a brief review of reductive dehalogenation of a-halocarbonyls, and is followed by an analysis and discussion of our results in the context of the studies by Israel et. al. and Oki et. al.
- Full Text:
- Date Issued: 2017
Synthesis of indium and lead phthalocyanine as photocatalysts for photodynamic antimicrobial chemotherapy and photo-oxidation of pollutants
- Authors: Oluwole, Oluyinka David
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5293 , vital:20805
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, Oluyinka David
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5293 , vital:20805
- Full Text:
- Date Issued: 2017
Reader in comedy
- Authors: Krueger, Anton
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225684 , vital:49248 , xlink:href="https://doi.org/10.1080/10137548.2017.1409523"
- Description: I really enjoyed this selection of excerpts on comedy. In 64 extracts, this comprehensive anthology covers 2375 years of mainly philosophical texts in 375 dense pages. From 360 BCE (Plato’s Philebus) to just the other day (Romanska’s Disability in Tragic and Comic Frame [2015]), this is an immense resource covering a lot of ground. The extracts don’t all apply specifically to theatre, though this is where the discussion begins, with the ancients. Later on, as new genres emerge, there are also entries relating to prose, film, story-telling and stand-up; but mainly, the writings have to do with laughter itself, and the role and function of comedy.
- Full Text:
- Date Issued: 2017
- Authors: Krueger, Anton
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225684 , vital:49248 , xlink:href="https://doi.org/10.1080/10137548.2017.1409523"
- Description: I really enjoyed this selection of excerpts on comedy. In 64 extracts, this comprehensive anthology covers 2375 years of mainly philosophical texts in 375 dense pages. From 360 BCE (Plato’s Philebus) to just the other day (Romanska’s Disability in Tragic and Comic Frame [2015]), this is an immense resource covering a lot of ground. The extracts don’t all apply specifically to theatre, though this is where the discussion begins, with the ancients. Later on, as new genres emerge, there are also entries relating to prose, film, story-telling and stand-up; but mainly, the writings have to do with laughter itself, and the role and function of comedy.
- Full Text:
- Date Issued: 2017
Rhenium complexes of benzazole derivatives
- Authors: Van Niekerk, Xandri
- Date: 2017
- Subjects: Rhenium Benzimidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21252 , vital:29467
- Description: A series of rhenium(I) complexes with monodentate benzazole ligands containing the fac-[Re(CO)3]+ was synthesized. The rhenium(I) compound [ReCl(Hmbt)2(CO)3] was prepared from the reaction of [Re(CO)5Cl] and 2-aminobenzothiazole (Hmbt) in toluene. The ligand coordinates in a monodentate manner via the thiazole nitrogen atom. A similar reaction between [Re(CO)5Cl] and N-(1,3-benzothiazol-2-yl)-2- chloroacetamide (Hbct) resulted in the formation of [ReCl(Hbct)(CO)3(NCMe)], where only one ligand binds per rhenium in a monodentate fashion. The reaction of ligands 2-mercaptobenzimidazole (Hmbi) (dibenzothiazol-2-yl)tetraazathiapentalene (Hdbt) with rhenium(I) gave [ReCl(Hmbi)2(CO)3] and [ReCl(Hdbt)2(CO)3] respectively. The study on the coordination behaviour between ethyl-(1H-benzimidazol-2-yl-sulfanyl) acetate (Hbsa) and [Re(CO)5Cl] surprisingly gave the dimeric species (μ-Cl)2[Re(Hbsa)(CO)3]2, where the two rhenium atoms are bridged by two chloro ligands. The coordination of Hbsa occurs through the imidazole nitrogen, leaving the ethoxy tail free on each Hbsa ligand. The coordination behaviour of benzimidazole and benzothiazole derivatives gave rhenium complexes in oxidation states I, III and V, where all the ligands coordinate as bidentate N,N-chelating ligands. The study on 2-(2-aminophenyl)-1-benzothiazole (Hapt) and 2-(2-aminophenyl)-1-benzimidazole (H2apz) with [ReVOCl3(PPh3)2] resulted in the formation of [ReVOCl2(apt)(OPPh3)] and [ReVCl2(apz)(PPh3)2](ReO4), respectively. 1,2-Bis(2-benzimidazole)-1,2-ethanediol (Hbed) and 2,6-bis(2- benzimidazol-2-yl)pyridine (H2bip) were studied towards rhenium(I) and rheniumV) respectively. The former gave a dimeric species (μ-bbi)[Re(CO)4]2 (H2bbi – bisbenzimidazole) by reaction with [Re(CO)5Cl], whereas H2bip produced the rhenium(III) cationic salt [ReCl3(H3bip)(PPh3)]Cl, where the ligand coordinates as a cationic H3bip+ with protonation of an uncoordinated imidazole nitrogen atom. The pyridine derivatives 2-hydrazino-pyridinyl-2-benzothiazole (Hhpt) and (E)-1-benzo[d]thiazol-2-yl)-2- (pyridin-2-ylmethylene)hydrazine (btp) were reacted with [Re(CO)5Cl]. The neutral complex [ReCl(Hhpt)(CO)3] was isolated upon reaction with Hhpt, where Hhpt coordinates as a neutral bidentate ligand. The reaction of [Re(CO)5Cl] with btp gave two different complexes when using different solvents. In methanol, [ReCl(btp)(CO)3] was isolated, whereas in toluene, the conjugate of btp (btp1) was formed which resulted in the formation of [ReCl(btp1)(CO)3]. The study on potentially bidentate thiourea derivatives containing a benzothiazole moiety towards [ReI(CO)3]+ and [ReVO]3+ cores gave rise to a wide variety of complexes. The reaction of [Re(CO)5Cl] with N-phenyl-N-(2-benzothiazole)thiourea (Hpbt) produced the rhenium(I) complex [Re(Hpbt)(pbt)(CO)3]. Hpbt coordinates both as a monodentate neutral ligand and as a bidentate monoanionic chelate. The study of the reaction between trans-[ReOCl3(PPh3)2] and Hpbt gave the rhenium(V) product [ReOCl2(pbt)(PPh3)], with pbt acting as a bidentate ligand. The reaction of 1-(1,3- benzothiazol-2-yl)-3-benzoylthiourea (Hbbt) with [Re(CO)5Cl] led to the isolation of [ReCl(Hbbt)(CO)3]. Similar reaction of Hbbt with trans-[ReOCl3(PPh3)2] gave the unique compound [ReOCl2(Hbnt)(PPh3)], where the ligand coordinates via the ketonic oxygen and a methine carbon. The complex [Re(Hmby)(mby)(CO)3] was isolated upon reacting [Re(CO)5Cl] with methylbenzothiazol-2-ylidenecarbamodithioate (Hmby), with Hmby coordinating as a monodentate neutral ligand and mby as a bidentate monoanionic chelate. The coordination behaviour of N-(benzothiazol-2-yl)-S,S’- dimethyldithiocarboimine (Hbdc) towards rhenium(I) led to the formation of [ReCl(Hbdc)(CO)3]. The reactivity of 1-(benzothiozol-2-yl)-3,3-dimethylthiourea (Hbdm), a derivative of Hmby, was studied with trans-[ReOCl3(PPh3)2] and trans- [ReO(OEt)I2(PPh3)2] producing the square pyramidal compound [ReOCl(bdm)2] and the salt [Re(bdm)2(MeCN)2]I3, respectively. Pyrazole derivatives containing a benzothiazole ring were studied towards rhenium in oxidation states +I and +V. The reaction between 2-(3,5-dimethylpyrazol-1-yl)benzothiazole (Hdmp) and [Re(CO)5Cl] gave the neutral rhenium complex [ReCl(Hdmp)(CO)3], whereas its reaction with [ReOCl3(PPh3)2] surprisingly results in the formation of a dimeric complex (μ-O)[ReOCl2(Hdmp)]2. The study on the reactivity of 1-(benzo[d]thiazol-2-yl)-4-methyl-1H-pyrrol-2-ol (Hbtm) with [Re(CO)5Cl] gave the unexpected trimer [Re(btm)(CO)3]3 containing the fac-[Re(CO)3]+ core. The ligand btm forms a bridge between each rhenium metal, serving as a bidentate ligand to one rhenium, and a monodentate ligand to another rhenium atom. The study on the coordination chemistry between trans-[ReOCl3(PPh3)2] and Hbtm gave two different complexes when using different solvents. In ethanol, [ReOCl(btm)(btm1)] formed, whereas [ReOCl(btm1)(btz)] (Hbtz = 1-(benzo[d]thiazol-2-yl)-4-(1-iminoethyl)-3- methyl-1H-pyrazol-5-ol) was isolated in acetonitrile. The reaction of cis-[ReO2I(PPh3)2] also gave two different products when using different solvents, where the respective solvents coordinate to the metal. The rhenium(V) compound [ReO(OMe)(btm)(btm1)] was formed in methanol, whereas [ReO(OEt)(btm)(btm1)] was formed in ethanol. The coordination chemistry of 2-(2-Benzothiazoleyl)-4,5,6,7-tetrahydro-2H-indazol-3-ol (Hbth) was studied towards [Re(CO)5Cl] and trans-[ReOCl3(PPh3)2]. The resulting complexes which formed are [ReCl(Hbth)(CO)3] and [ReOCl(bth)(bth1)] respectively. The reactivity of potentially tridentate Schiff base ligands towards rhenium(I) and (V) was studied. The rhenium(I) precursor [Re(CO)5Cl] was reacted with (E)-1- (benzo[d]thiazol-2-yl)-2-(phenol-2-ylmethylene)hydrazine (H3bph) to give [ReCl(CO)3(H3bph)], which contains the kinetically inert fac-[Re(CO)3]+ core coordinated to a neutral bidentate ligand. The reaction of [ReO2(py)4Cl] with H3bph gave the dimeric species (μ-O)[ReO(Hbph)(py)]2, where the ligand coordinates as a tridentate dianionic chelate. A similar complex was isolated with (E)-1- (benzo[d]thiazol-2-yl)-2-(2,4-dihydroxy-2-ylmethylene)hydrazine (H3bdh) to give (μ-O)[ReO(Hbdh)(py)]2. The reaction of trans-[ReOCl3(PPh3)2] with H3bph afforded [Re(abt)(imp)Cl2(PPh3)] (abt = 2-aminobenzothiazole, imp = 2-(iminomethyl)phenol), where the ligand broke up into two fragments, both of which coordinated without any modification. The dioxo rhenium precursor cis-[ReO2I(PPh3)2] gave [ReO(Hbdh)(imp)] upon reaction with H3bdh. Ligand imp coordinates as a bidentate monoanionic ligand via the imine nitrogen and deprotonated phenolic oxygen and ligand Hbdh coordinatesas a tridentate dianionic chelate.
- Full Text:
- Date Issued: 2017
- Authors: Van Niekerk, Xandri
- Date: 2017
- Subjects: Rhenium Benzimidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21252 , vital:29467
- Description: A series of rhenium(I) complexes with monodentate benzazole ligands containing the fac-[Re(CO)3]+ was synthesized. The rhenium(I) compound [ReCl(Hmbt)2(CO)3] was prepared from the reaction of [Re(CO)5Cl] and 2-aminobenzothiazole (Hmbt) in toluene. The ligand coordinates in a monodentate manner via the thiazole nitrogen atom. A similar reaction between [Re(CO)5Cl] and N-(1,3-benzothiazol-2-yl)-2- chloroacetamide (Hbct) resulted in the formation of [ReCl(Hbct)(CO)3(NCMe)], where only one ligand binds per rhenium in a monodentate fashion. The reaction of ligands 2-mercaptobenzimidazole (Hmbi) (dibenzothiazol-2-yl)tetraazathiapentalene (Hdbt) with rhenium(I) gave [ReCl(Hmbi)2(CO)3] and [ReCl(Hdbt)2(CO)3] respectively. The study on the coordination behaviour between ethyl-(1H-benzimidazol-2-yl-sulfanyl) acetate (Hbsa) and [Re(CO)5Cl] surprisingly gave the dimeric species (μ-Cl)2[Re(Hbsa)(CO)3]2, where the two rhenium atoms are bridged by two chloro ligands. The coordination of Hbsa occurs through the imidazole nitrogen, leaving the ethoxy tail free on each Hbsa ligand. The coordination behaviour of benzimidazole and benzothiazole derivatives gave rhenium complexes in oxidation states I, III and V, where all the ligands coordinate as bidentate N,N-chelating ligands. The study on 2-(2-aminophenyl)-1-benzothiazole (Hapt) and 2-(2-aminophenyl)-1-benzimidazole (H2apz) with [ReVOCl3(PPh3)2] resulted in the formation of [ReVOCl2(apt)(OPPh3)] and [ReVCl2(apz)(PPh3)2](ReO4), respectively. 1,2-Bis(2-benzimidazole)-1,2-ethanediol (Hbed) and 2,6-bis(2- benzimidazol-2-yl)pyridine (H2bip) were studied towards rhenium(I) and rheniumV) respectively. The former gave a dimeric species (μ-bbi)[Re(CO)4]2 (H2bbi – bisbenzimidazole) by reaction with [Re(CO)5Cl], whereas H2bip produced the rhenium(III) cationic salt [ReCl3(H3bip)(PPh3)]Cl, where the ligand coordinates as a cationic H3bip+ with protonation of an uncoordinated imidazole nitrogen atom. The pyridine derivatives 2-hydrazino-pyridinyl-2-benzothiazole (Hhpt) and (E)-1-benzo[d]thiazol-2-yl)-2- (pyridin-2-ylmethylene)hydrazine (btp) were reacted with [Re(CO)5Cl]. The neutral complex [ReCl(Hhpt)(CO)3] was isolated upon reaction with Hhpt, where Hhpt coordinates as a neutral bidentate ligand. The reaction of [Re(CO)5Cl] with btp gave two different complexes when using different solvents. In methanol, [ReCl(btp)(CO)3] was isolated, whereas in toluene, the conjugate of btp (btp1) was formed which resulted in the formation of [ReCl(btp1)(CO)3]. The study on potentially bidentate thiourea derivatives containing a benzothiazole moiety towards [ReI(CO)3]+ and [ReVO]3+ cores gave rise to a wide variety of complexes. The reaction of [Re(CO)5Cl] with N-phenyl-N-(2-benzothiazole)thiourea (Hpbt) produced the rhenium(I) complex [Re(Hpbt)(pbt)(CO)3]. Hpbt coordinates both as a monodentate neutral ligand and as a bidentate monoanionic chelate. The study of the reaction between trans-[ReOCl3(PPh3)2] and Hpbt gave the rhenium(V) product [ReOCl2(pbt)(PPh3)], with pbt acting as a bidentate ligand. The reaction of 1-(1,3- benzothiazol-2-yl)-3-benzoylthiourea (Hbbt) with [Re(CO)5Cl] led to the isolation of [ReCl(Hbbt)(CO)3]. Similar reaction of Hbbt with trans-[ReOCl3(PPh3)2] gave the unique compound [ReOCl2(Hbnt)(PPh3)], where the ligand coordinates via the ketonic oxygen and a methine carbon. The complex [Re(Hmby)(mby)(CO)3] was isolated upon reacting [Re(CO)5Cl] with methylbenzothiazol-2-ylidenecarbamodithioate (Hmby), with Hmby coordinating as a monodentate neutral ligand and mby as a bidentate monoanionic chelate. The coordination behaviour of N-(benzothiazol-2-yl)-S,S’- dimethyldithiocarboimine (Hbdc) towards rhenium(I) led to the formation of [ReCl(Hbdc)(CO)3]. The reactivity of 1-(benzothiozol-2-yl)-3,3-dimethylthiourea (Hbdm), a derivative of Hmby, was studied with trans-[ReOCl3(PPh3)2] and trans- [ReO(OEt)I2(PPh3)2] producing the square pyramidal compound [ReOCl(bdm)2] and the salt [Re(bdm)2(MeCN)2]I3, respectively. Pyrazole derivatives containing a benzothiazole ring were studied towards rhenium in oxidation states +I and +V. The reaction between 2-(3,5-dimethylpyrazol-1-yl)benzothiazole (Hdmp) and [Re(CO)5Cl] gave the neutral rhenium complex [ReCl(Hdmp)(CO)3], whereas its reaction with [ReOCl3(PPh3)2] surprisingly results in the formation of a dimeric complex (μ-O)[ReOCl2(Hdmp)]2. The study on the reactivity of 1-(benzo[d]thiazol-2-yl)-4-methyl-1H-pyrrol-2-ol (Hbtm) with [Re(CO)5Cl] gave the unexpected trimer [Re(btm)(CO)3]3 containing the fac-[Re(CO)3]+ core. The ligand btm forms a bridge between each rhenium metal, serving as a bidentate ligand to one rhenium, and a monodentate ligand to another rhenium atom. The study on the coordination chemistry between trans-[ReOCl3(PPh3)2] and Hbtm gave two different complexes when using different solvents. In ethanol, [ReOCl(btm)(btm1)] formed, whereas [ReOCl(btm1)(btz)] (Hbtz = 1-(benzo[d]thiazol-2-yl)-4-(1-iminoethyl)-3- methyl-1H-pyrazol-5-ol) was isolated in acetonitrile. The reaction of cis-[ReO2I(PPh3)2] also gave two different products when using different solvents, where the respective solvents coordinate to the metal. The rhenium(V) compound [ReO(OMe)(btm)(btm1)] was formed in methanol, whereas [ReO(OEt)(btm)(btm1)] was formed in ethanol. The coordination chemistry of 2-(2-Benzothiazoleyl)-4,5,6,7-tetrahydro-2H-indazol-3-ol (Hbth) was studied towards [Re(CO)5Cl] and trans-[ReOCl3(PPh3)2]. The resulting complexes which formed are [ReCl(Hbth)(CO)3] and [ReOCl(bth)(bth1)] respectively. The reactivity of potentially tridentate Schiff base ligands towards rhenium(I) and (V) was studied. The rhenium(I) precursor [Re(CO)5Cl] was reacted with (E)-1- (benzo[d]thiazol-2-yl)-2-(phenol-2-ylmethylene)hydrazine (H3bph) to give [ReCl(CO)3(H3bph)], which contains the kinetically inert fac-[Re(CO)3]+ core coordinated to a neutral bidentate ligand. The reaction of [ReO2(py)4Cl] with H3bph gave the dimeric species (μ-O)[ReO(Hbph)(py)]2, where the ligand coordinates as a tridentate dianionic chelate. A similar complex was isolated with (E)-1- (benzo[d]thiazol-2-yl)-2-(2,4-dihydroxy-2-ylmethylene)hydrazine (H3bdh) to give (μ-O)[ReO(Hbdh)(py)]2. The reaction of trans-[ReOCl3(PPh3)2] with H3bph afforded [Re(abt)(imp)Cl2(PPh3)] (abt = 2-aminobenzothiazole, imp = 2-(iminomethyl)phenol), where the ligand broke up into two fragments, both of which coordinated without any modification. The dioxo rhenium precursor cis-[ReO2I(PPh3)2] gave [ReO(Hbdh)(imp)] upon reaction with H3bdh. Ligand imp coordinates as a bidentate monoanionic ligand via the imine nitrogen and deprotonated phenolic oxygen and ligand Hbdh coordinatesas a tridentate dianionic chelate.
- Full Text:
- Date Issued: 2017
Rhodes University Research Report 2017 : a year in review
- Gillitt, Tarryn, Macgregor, Jill, Mantolo, Thumeka, Roberts, Jaine
- Authors: Gillitt, Tarryn , Macgregor, Jill , Mantolo, Thumeka , Roberts, Jaine
- Date: 2017
- Subjects: Rhodes University -- Research
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/72172 , vital:30012
- Description: From Foreword by Dr Sizwe Mabizela, Vice-Chancellor: Many of the goals of our recently completed Institutional Development Plan have to do with retaining and improving our research and scholarly contribution as a university, and ensuring that we not only generate dependable knowledge, but that the knowledge that we create has a positive impact on the social and natural world around us. In summary, our goals are to 1. Maintain and strengthen our general formative degree offering and the research, teaching, and community engagement nexus which enables our students to access powerful knowledge; 2. Enable access to all academically-qualifying students and provide them with conditions which allow them to flourish as critical and engaged citizens; 3. Maintain and strengthen our unique institutional niche as a research-intensive university outside a major urban area; 4. Ensure financial and environmental sustainability practices through good governance, leadership and management; 5. Attract, nurture and retain staff of high-calibre and maintain an inclusive, welcoming, affirming and positive intellectual environment; 6. Provide relevant and appropriate academic infrastructure, equipment and facilities to support our academic project; and 7. Promote Rhodes University as an institution for the public good in local, provincial, national and international contexts. The plan calls upon all of us to re-imagine our University as one in which sustainability permeates every aspect of our academic endeavour, including an elevated sense of awareness and responsibility of our graduates for building sustainable communities. It calls upon us to ensure that we are simultaneously locally responsive and globally engaged. It calls upon us to work towards advancing social justice and do all that we can to restore the dignity and humanity of those who were treated as lesser beings by the previous dispensation. And it calls upon us to remind ourselves that our university does not exist in a vacuum. It exists within a social, cultural and economic milieu, and has an important role to play in lifting the standard of living of our local community.
- Full Text:
- Date Issued: 2017
- Authors: Gillitt, Tarryn , Macgregor, Jill , Mantolo, Thumeka , Roberts, Jaine
- Date: 2017
- Subjects: Rhodes University -- Research
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/72172 , vital:30012
- Description: From Foreword by Dr Sizwe Mabizela, Vice-Chancellor: Many of the goals of our recently completed Institutional Development Plan have to do with retaining and improving our research and scholarly contribution as a university, and ensuring that we not only generate dependable knowledge, but that the knowledge that we create has a positive impact on the social and natural world around us. In summary, our goals are to 1. Maintain and strengthen our general formative degree offering and the research, teaching, and community engagement nexus which enables our students to access powerful knowledge; 2. Enable access to all academically-qualifying students and provide them with conditions which allow them to flourish as critical and engaged citizens; 3. Maintain and strengthen our unique institutional niche as a research-intensive university outside a major urban area; 4. Ensure financial and environmental sustainability practices through good governance, leadership and management; 5. Attract, nurture and retain staff of high-calibre and maintain an inclusive, welcoming, affirming and positive intellectual environment; 6. Provide relevant and appropriate academic infrastructure, equipment and facilities to support our academic project; and 7. Promote Rhodes University as an institution for the public good in local, provincial, national and international contexts. The plan calls upon all of us to re-imagine our University as one in which sustainability permeates every aspect of our academic endeavour, including an elevated sense of awareness and responsibility of our graduates for building sustainable communities. It calls upon us to ensure that we are simultaneously locally responsive and globally engaged. It calls upon us to work towards advancing social justice and do all that we can to restore the dignity and humanity of those who were treated as lesser beings by the previous dispensation. And it calls upon us to remind ourselves that our university does not exist in a vacuum. It exists within a social, cultural and economic milieu, and has an important role to play in lifting the standard of living of our local community.
- Full Text:
- Date Issued: 2017
Attitudes of community stakeholders towards stigmatization of people living with HIV/AIDS in Highland View, linked to St Patrick's Clinic, Bizana, Eastern Cape
- Authors: Nkalane, Athenkosi
- Date: 2017
- Subjects: AIDS (Disease)-- Social aspects -- South Africa -- Eastern Cape HIV-positive persons -- South Africa -- Eastern Cape Stigma (Social psychology)
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/9446 , vital:34352
- Description: The researcher attempted to investigate attitudes of community stakeholders towards stigmatization of people living with HIV/AIDS (PLWHA). This is because people living with HIV/AIDS are usually subjected to negative and positive attitudes in South African communities. The study made use of a case study as a specific research design which was explorative and descriptive. The study employed in-depth interviews, focus group discussions and secondary data sources to collect data. The study was a cross-sectional and adopted a non-probability sampling methodology, but specifically purposive technique. The study used 25 participants who consisted of 12 PLWHA, 5 nurses, and 8 selected community members. The data were analyzed through content thematic analysis. The findings that emanated from the study were: awareness of stigmatizing attitudes subjected to people living with HIV/AIDS (PLWHA); the attitudes displayed towards PLWHA, the drivers of stigma; the impact of stigma on PLWHA; PLWHA suffers immense psychosocial deficit; PLWHA face a state of abject poverty; PLWHA faces Psycho-emotional deficit; the secrecy surrounding the virus forms a fertile ground for infection; fear of contagion; stigma confounds chances of HIV/AIDS disclosure and issues of confidentiality. The study recommended that: the government should prioritize the PLWHA’s human rights; adoption of social media platforms to raise awareness and education of HIV/AIDS; collaboration between the Department of Health and the Department of Traditional affairs; invention of a youth-based psycho-emotional programme; and establishment of in-depth community supported interventions.
- Full Text:
- Date Issued: 2017
- Authors: Nkalane, Athenkosi
- Date: 2017
- Subjects: AIDS (Disease)-- Social aspects -- South Africa -- Eastern Cape HIV-positive persons -- South Africa -- Eastern Cape Stigma (Social psychology)
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/9446 , vital:34352
- Description: The researcher attempted to investigate attitudes of community stakeholders towards stigmatization of people living with HIV/AIDS (PLWHA). This is because people living with HIV/AIDS are usually subjected to negative and positive attitudes in South African communities. The study made use of a case study as a specific research design which was explorative and descriptive. The study employed in-depth interviews, focus group discussions and secondary data sources to collect data. The study was a cross-sectional and adopted a non-probability sampling methodology, but specifically purposive technique. The study used 25 participants who consisted of 12 PLWHA, 5 nurses, and 8 selected community members. The data were analyzed through content thematic analysis. The findings that emanated from the study were: awareness of stigmatizing attitudes subjected to people living with HIV/AIDS (PLWHA); the attitudes displayed towards PLWHA, the drivers of stigma; the impact of stigma on PLWHA; PLWHA suffers immense psychosocial deficit; PLWHA face a state of abject poverty; PLWHA faces Psycho-emotional deficit; the secrecy surrounding the virus forms a fertile ground for infection; fear of contagion; stigma confounds chances of HIV/AIDS disclosure and issues of confidentiality. The study recommended that: the government should prioritize the PLWHA’s human rights; adoption of social media platforms to raise awareness and education of HIV/AIDS; collaboration between the Department of Health and the Department of Traditional affairs; invention of a youth-based psycho-emotional programme; and establishment of in-depth community supported interventions.
- Full Text:
- Date Issued: 2017
Benthic algal communities of shallow reefs in the Eastern Cape: availability of abalone habitat
- Authors: Witte, Andrew Dennis
- Date: 2017
- Subjects: Reef ecology -- South Africa -- Eastern Cape Abalone fisheries -- Habitat -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12032 , vital:27021
- Description: Marine ranching has been identified as an alternative to traditional aquacultural rearing and growing organisms for consumption. In the Eastern Cape, abalone ranching is a new and experimental industry. The aims of the research were to: first develop a GIS model to assist management in site selection for abalone seeding; and secondly to develop and standardize the sampling methodology in order to ground truth the sites, and assist in the monitoring and habitat identification of abalone. The GIS model developed in Chapter 3 was created using an unsupervised classification and fuzzy logic approach. Both vector and raster datasets were utilized to represent 7 different layers. Predominantly satellite imagery was used to classify the different substrate groups according to pixel colour signatures. The basic process was to apply a fuzzy rule set (membership) to rasters which gave an output raster (Fuzzification). The membership output rasters were overlaid which creates a single model output. It was found that model accuracy increased significantly as more layers were overlaid, due to the high variability within each of the individual layers. Model ground-truthing showed a strong and significant correlation (r2 = 0.91; p < 0.001) between the model outputs and actual site suitability based on in situ evaluation. Chapter 4 describes the investigation towards the optimal sampling methods for abalone ranching habitat assessments. Both destructive sampling methods and imagery methods were considered as methods of data collection. The study also evaluated whether quadrat and transects were going to be suitable methods to assess sites, and what size or length respectively they should be to collect the appropriate data. Transect length showed great variation according to the factor assessed. A transect of 15 metres was found to be optimal. Abalone counts showed no significant (p = 0.1) change in the Coefficent of Variance (CV) for transect lengths greater than 15m, and had a mean of 0.2 abalone per metre. Quadrat size showed a significant difference in functional group richness between quadrat sizes of 0.0625m2, and 0.25m2 but no difference between 0.25m2 and 1m2 quadrats for both scape and photographic quadrats. It was also found that between 5 and 10 replicates (p = 0.08) represents the functional groups appropriately using quadrats and that a 0.25m2 quadrat is most suitable for sampling. Chapter 5 describes the benthic community structure of Cape Recife shallow water reefs. Using the standardized methodology previously mentioned, 45 sites were assessed to identify the community structure. These sites were grouped into 5 different groups influenced by depth and substrate, as well as functional group composition according to a Wards classification. The community structure showed that depth and substrate play a significant role (p < 0.05) in the community type. There is also a significant relationship (p < 0.05) between complexity, rugosity, abalone presence and substrate. During this study the basic protocols for site selection and benthic community monitoring have been developed to support the abalone ranching initiative in the Cape Recife area. It has also provided a baseline of the benthic community in the ranching concession area which will be used as a benchmark for future monitoring efforts. The site selection, sampling, and monitoring methods developed during the course of this work have now been rolled out as Standard Operating Procedures for the ranching programme in this area.
- Full Text:
- Date Issued: 2017
- Authors: Witte, Andrew Dennis
- Date: 2017
- Subjects: Reef ecology -- South Africa -- Eastern Cape Abalone fisheries -- Habitat -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12032 , vital:27021
- Description: Marine ranching has been identified as an alternative to traditional aquacultural rearing and growing organisms for consumption. In the Eastern Cape, abalone ranching is a new and experimental industry. The aims of the research were to: first develop a GIS model to assist management in site selection for abalone seeding; and secondly to develop and standardize the sampling methodology in order to ground truth the sites, and assist in the monitoring and habitat identification of abalone. The GIS model developed in Chapter 3 was created using an unsupervised classification and fuzzy logic approach. Both vector and raster datasets were utilized to represent 7 different layers. Predominantly satellite imagery was used to classify the different substrate groups according to pixel colour signatures. The basic process was to apply a fuzzy rule set (membership) to rasters which gave an output raster (Fuzzification). The membership output rasters were overlaid which creates a single model output. It was found that model accuracy increased significantly as more layers were overlaid, due to the high variability within each of the individual layers. Model ground-truthing showed a strong and significant correlation (r2 = 0.91; p < 0.001) between the model outputs and actual site suitability based on in situ evaluation. Chapter 4 describes the investigation towards the optimal sampling methods for abalone ranching habitat assessments. Both destructive sampling methods and imagery methods were considered as methods of data collection. The study also evaluated whether quadrat and transects were going to be suitable methods to assess sites, and what size or length respectively they should be to collect the appropriate data. Transect length showed great variation according to the factor assessed. A transect of 15 metres was found to be optimal. Abalone counts showed no significant (p = 0.1) change in the Coefficent of Variance (CV) for transect lengths greater than 15m, and had a mean of 0.2 abalone per metre. Quadrat size showed a significant difference in functional group richness between quadrat sizes of 0.0625m2, and 0.25m2 but no difference between 0.25m2 and 1m2 quadrats for both scape and photographic quadrats. It was also found that between 5 and 10 replicates (p = 0.08) represents the functional groups appropriately using quadrats and that a 0.25m2 quadrat is most suitable for sampling. Chapter 5 describes the benthic community structure of Cape Recife shallow water reefs. Using the standardized methodology previously mentioned, 45 sites were assessed to identify the community structure. These sites were grouped into 5 different groups influenced by depth and substrate, as well as functional group composition according to a Wards classification. The community structure showed that depth and substrate play a significant role (p < 0.05) in the community type. There is also a significant relationship (p < 0.05) between complexity, rugosity, abalone presence and substrate. During this study the basic protocols for site selection and benthic community monitoring have been developed to support the abalone ranching initiative in the Cape Recife area. It has also provided a baseline of the benthic community in the ranching concession area which will be used as a benchmark for future monitoring efforts. The site selection, sampling, and monitoring methods developed during the course of this work have now been rolled out as Standard Operating Procedures for the ranching programme in this area.
- Full Text:
- Date Issued: 2017
Synthesis of indium and lead phthalocyanine as photocatalysts for photodynamic antimicrobial chemotherapy and photo-oxidation of pollutants
- Authors: Osifeko, Olawale L
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5221 , vital:20790
- Description: This thesis explores the synthesis of metallophthalocyanines as potential photosensitizers for application in photodynamic antimicrobial chemotherapy and phototransformation of environmental pollutants. The metallophthalocyanines containing amino substituent were conjugated with magnetic nanoparticle and semiconductor quantum dots via an amide bond and by chemisorption onto gold nanoparticles surface. Techniques such as time-resolved fluorescence measurements, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis, fourier transform infrared (FTIR), nuclear magnetic resonance (¹H, ¹³C, and cozy of symmetrical phthalocyanine), electronic spectroscopy, as well as mass spectroscopy were employed to characterize all metallophthalocyanines. Quarternized pyridyloxy substituted phthalocyanine and asymmetric (AB3) metallophthalocyanines were embedded in electrospun polystyrene fiber. General trends are described for quantum yields of fluorescence, triplet, singlet oxygen and photodegradation as well as lifetimes of fluorescence and triplet state of the compounds. There is an increase in triplet quantum yield for Pcs in the presence of gold nanoparticles (AuNPs) and semiconductor quantum dots (QDs), but not in the presence of magnetic nanoparticles (MNPs). Photodynamic inactivation of Escherichia coli with the quarternized photosensitizers at low concentrations totally inactivate the bacteria compared to non-charged photosensitiser. Also, a similar trend was observed for the magnetic nanoparticles conjugates. Photooxidations of bisphenol A and 4-chlorophenol were carried out in this study using two asymmetric Indium(III) phthalocyanines photosensitizers. The photooxidation reactions were compared with those of a symmetrical indium(III) phthalocyanines containing four quaternized 4-pyridyloxy substituents. The complexes were embedded in electrospun polystyrene fiber for heterogeneous photocatalysis. The immobilized photosensitizers possess good singlet oxygen generation potentials in aqueous media. The asymmetrical phthalocyanine containing 4-pyridylsulfanyl and one aminophenoxy showed the best photocatalytic behavior.
- Full Text:
- Date Issued: 2017
- Authors: Osifeko, Olawale L
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5221 , vital:20790
- Description: This thesis explores the synthesis of metallophthalocyanines as potential photosensitizers for application in photodynamic antimicrobial chemotherapy and phototransformation of environmental pollutants. The metallophthalocyanines containing amino substituent were conjugated with magnetic nanoparticle and semiconductor quantum dots via an amide bond and by chemisorption onto gold nanoparticles surface. Techniques such as time-resolved fluorescence measurements, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis, fourier transform infrared (FTIR), nuclear magnetic resonance (¹H, ¹³C, and cozy of symmetrical phthalocyanine), electronic spectroscopy, as well as mass spectroscopy were employed to characterize all metallophthalocyanines. Quarternized pyridyloxy substituted phthalocyanine and asymmetric (AB3) metallophthalocyanines were embedded in electrospun polystyrene fiber. General trends are described for quantum yields of fluorescence, triplet, singlet oxygen and photodegradation as well as lifetimes of fluorescence and triplet state of the compounds. There is an increase in triplet quantum yield for Pcs in the presence of gold nanoparticles (AuNPs) and semiconductor quantum dots (QDs), but not in the presence of magnetic nanoparticles (MNPs). Photodynamic inactivation of Escherichia coli with the quarternized photosensitizers at low concentrations totally inactivate the bacteria compared to non-charged photosensitiser. Also, a similar trend was observed for the magnetic nanoparticles conjugates. Photooxidations of bisphenol A and 4-chlorophenol were carried out in this study using two asymmetric Indium(III) phthalocyanines photosensitizers. The photooxidation reactions were compared with those of a symmetrical indium(III) phthalocyanines containing four quaternized 4-pyridyloxy substituents. The complexes were embedded in electrospun polystyrene fiber for heterogeneous photocatalysis. The immobilized photosensitizers possess good singlet oxygen generation potentials in aqueous media. The asymmetrical phthalocyanine containing 4-pyridylsulfanyl and one aminophenoxy showed the best photocatalytic behavior.
- Full Text:
- Date Issued: 2017
Tetra 4-(propargyloxy)phenoxy phthalocyanines: synthesis, spectroscopic, nonlinear optical and electrocatalytic properties
- Authors: Mwanza, Daniel
- Date: 2017
- Subjects: Phthalocyanines , Nonlinear optics , Electrocatalysis , Spectrum analysis , Thermogravimetry , Phthalocyanines Spectra
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65144 , vital:28695
- Description: This study presents the synthesis, spectroscopic, photophysical and theoretical characterisation of metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (MnTPrOPhOPc) tetra 4-(4-propargyloxy) phenoxy phthalocyanines. Thermal analysis using thermogravimetric analysis (TGA) confirmed the excellent thermal stability of synthesized tetra 4-(4- propargyloxy) phenoxy phthalocyanines. The metal complexes, CoTPrOPhOPc and MnTPrOPhOPc, exhibited better thermal stability when compared to H2TPrOPhOPc. The residual percentage weight remaining was approximately 70% for CoTPrOPhOPc and MnTPrOPhOPc and 45% for H2TPrOPhOPc after 600°C, clearly confirming the stability of the metal complexes. The MTPrOPhOPcs (where M = H2, Co and Mn) complexes exhibited excellent nonlinear optical properties with strong reverse saturable absorption (RSA), especially when 560 nm excitation laser was used. Their nonlinear optical properties followed this trend: H2TPrOPhOPc > CoTPrOPhOPc > MnTPrOPhOPc. According to the trend observed, the H2TPrOPhOPc was an excellent nonlinear optical limiter when compared to the CoTPrOPhOPc and MnTPrOPhOPc. All the investigated complexes exhibited optical limiting properties comparable to the phthalocyanine complexes reported in the literature. The MTPrOPhOPc complexes were further studied for their electrocatalytic and electroanalytical properties towards the detection of hydrogen peroxide. For the electrocatalytic studies, the synthesized complexes were immobilized onto gold electrode surfaces pre-functionalized with phenylazide (Au-PAz) monolayer. Copper (I) catalyzed alkynyl-azide cycloaddition reaction was used to covalently immobilize the MTPrOPhOPcs onto the gold electrode surfaces to form Au-PAz-MTPrOPhOPc. The MTPrOPhOPcs modified gold surfaces (Au-PAz-MTPrOPhOPc) exhibited good reproducibility and stability in various electrolyte conditions. Electrochemical and surface characterisation of the functionalised gold electrode surfaces confirmed the presence of the MTPrOPhOPcs and their electroanalysis was excellent towards electrocatalytic reduction of H2O2, with the limit of detection (LoD) and limit of quantification (LoQ) in the ^M range. The electrocatalytic reduction peaks for H2O2 were observed at -0.37 V for Au-PAz-MnTPrOPhOPc and -0.31 V for Au-PAz-CoTPrOPhOPc when Ag|AgCl pseudo-reference electrode was used. The Au-PAz-MnTPrOPhOPc and Au- PAz-CoTPrOPhOPc gold electrode surfaces showed good sensitivity and reproducibility towards the electrocatalytic reduction of hydrogen peroxide in pH 7.4 phosphate buffer solution. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
- Authors: Mwanza, Daniel
- Date: 2017
- Subjects: Phthalocyanines , Nonlinear optics , Electrocatalysis , Spectrum analysis , Thermogravimetry , Phthalocyanines Spectra
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65144 , vital:28695
- Description: This study presents the synthesis, spectroscopic, photophysical and theoretical characterisation of metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (MnTPrOPhOPc) tetra 4-(4-propargyloxy) phenoxy phthalocyanines. Thermal analysis using thermogravimetric analysis (TGA) confirmed the excellent thermal stability of synthesized tetra 4-(4- propargyloxy) phenoxy phthalocyanines. The metal complexes, CoTPrOPhOPc and MnTPrOPhOPc, exhibited better thermal stability when compared to H2TPrOPhOPc. The residual percentage weight remaining was approximately 70% for CoTPrOPhOPc and MnTPrOPhOPc and 45% for H2TPrOPhOPc after 600°C, clearly confirming the stability of the metal complexes. The MTPrOPhOPcs (where M = H2, Co and Mn) complexes exhibited excellent nonlinear optical properties with strong reverse saturable absorption (RSA), especially when 560 nm excitation laser was used. Their nonlinear optical properties followed this trend: H2TPrOPhOPc > CoTPrOPhOPc > MnTPrOPhOPc. According to the trend observed, the H2TPrOPhOPc was an excellent nonlinear optical limiter when compared to the CoTPrOPhOPc and MnTPrOPhOPc. All the investigated complexes exhibited optical limiting properties comparable to the phthalocyanine complexes reported in the literature. The MTPrOPhOPc complexes were further studied for their electrocatalytic and electroanalytical properties towards the detection of hydrogen peroxide. For the electrocatalytic studies, the synthesized complexes were immobilized onto gold electrode surfaces pre-functionalized with phenylazide (Au-PAz) monolayer. Copper (I) catalyzed alkynyl-azide cycloaddition reaction was used to covalently immobilize the MTPrOPhOPcs onto the gold electrode surfaces to form Au-PAz-MTPrOPhOPc. The MTPrOPhOPcs modified gold surfaces (Au-PAz-MTPrOPhOPc) exhibited good reproducibility and stability in various electrolyte conditions. Electrochemical and surface characterisation of the functionalised gold electrode surfaces confirmed the presence of the MTPrOPhOPcs and their electroanalysis was excellent towards electrocatalytic reduction of H2O2, with the limit of detection (LoD) and limit of quantification (LoQ) in the ^M range. The electrocatalytic reduction peaks for H2O2 were observed at -0.37 V for Au-PAz-MnTPrOPhOPc and -0.31 V for Au-PAz-CoTPrOPhOPc when Ag|AgCl pseudo-reference electrode was used. The Au-PAz-MnTPrOPhOPc and Au- PAz-CoTPrOPhOPc gold electrode surfaces showed good sensitivity and reproducibility towards the electrocatalytic reduction of hydrogen peroxide in pH 7.4 phosphate buffer solution. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
Workplace health promotion: a case of Rhodes University support staff
- Chigumete, Tinatsei Gabriella
- Authors: Chigumete, Tinatsei Gabriella
- Date: 2017
- Subjects: Rhodes University -- Employees -- Health and hygiene , Employee health promotion -- South Africa -- Makhanda
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44509 , vital:25414
- Description: Background: Non-communicable diseases are rapidly advancing as leading causes of morbidity and mortality across social classes, exerting pressure on existing financial, organizational, and human resources. Health promotion is a common practice in the prevention of noncommunicable diseases, but workplace health promotion has not yet been well established in many workplaces. Identification of past workplace initiatives and exploring their facilitating and limiting factors is thus important to take into consideration when planning future initiatives. Well-informed and guided workplace health promotion initiatives are essential to improve the general health of staff, and these also need to take the broader cultural, socioeconomic, and environmental factors influencing non-communicable diseases in the target population into account. This two-phase study was conducted at Rhodes University. A needs assessment was conducted to identify current policies and practices of workplace health promotion and to identify any shortcomings of the initiatives that have previously been attempted to raise awareness of non-communicable diseases at Rhodes University. The second phase of this project aimed to address concerns raised in the first phase through a health promotion initiative for support staff that focuses on the prevention of noncommunicable diseases through heart healthy diets and physical activity. Method: The first phase of the current study involved working with the support staff and key stakeholders. Using the participatory action research approach and the PRECEDE-PROCEED model to guide the research, 11 semi-structured interviews with key stakeholders and 10 focus group discussions were conducted with support staff members to identify factors affecting workplace health promotion. Participant opinions on how to improve these initiatives were sought. The participants were asked to identify areas on which the intended intervention should focus, as well as to identify their preferred means of communicating health messages. During this phase, a group of support staff members who volunteered their involvement in the design and delivery of the educational intervention was also identified. They chose to go by the name, the Health Awareness Group.In an interim phase of the study, three health information leaflets informed by the results from the above activities were designed. These leaflets underwent a series of qualitative evaluations by other health professionals, a culture and African languages expert, and the Health Awareness Group, to assess content validity, context specificity, and cultural appropriateness for the target group. A series of quantitative tests for readability, suitability, and actionability was also conducted. The health information leaflets were then used as written materials in the educational intervention of the project. Members of the Health Awareness Group were also trained as peer educators through a series of workshops. This enabled them to promote and raise awareness of heart healthy diets and physical activity to others in the workplace. Workshops were participatory in nature and were guided by the Social Cognitive Theory. They were also equipped with the completed health information leaflets to distribute to their peers and to use as reference sources of information when needed. Results: Participants in the semi-structured interviews reported that some health promotion initiatives have previously been attempted and advertised to support staff, but the turnout was poor and most staff did not seem to understand the health benefits of these initiatives. The support staff, in turn, stated that most health talks were conducted in English, contained medical jargon, and that they would have preferred these initiatives either to be simplified or presented in their home language, and to display cultural sensitivity. Support staff have also reported that advertisements were too cliche to elicit their interest. They also suggested incentivising initiatives for better participation. Another key suggestion was to facilitate these initiatives in the university departments they work or other convenient venues, rather than at central venues. It was also suggested that these initiatives be part of the work calendar, as they are often 'impromptu' and, as a result, staff members did not have enough notice to take time off work. Several staff members requested 're-runs of these initiatives because one-time show cases are often inadequate'. Colourful visual representations on posters or leaflets, short plays or films were also proposed as modes of delivering health information. During the design of the material to be used for this project's intended intervention, the health information leaflets were deemed readable, suitable, actionable, context-specific, and culturally appropriate. Workshops conducted during Phase 2 of the study proved to be valuable in training peer educators. Members of the Health Awareness Group also deemed the workshops useful, and reported their readiness to be agents of change in the workplace. Conclusions: Based on the input of key stakeholders and support staff, health promotion policies and protocols for non-communicable diseases have not yet been developed. Health promotion initiatives, especially for support staff, that address non-communicable diseases have previously been attempted at the university but were not well-received. Factors affecting workplace health promotion were identified. Knowledge of these factors was useful in designing and tailoring the written educational materials and the educational intervention to the needs of the support staff and to redress the deficiencies of previous initiatives. The health leaflets were deemed appropriate for use by the target population. They addressed pertinent information needs. The health information leaflets and workshops were useful in equipping the Health Awareness Group with knowledge on heart healthy diets and promotion of physical activity. Continued the involvement of representatives from the Human Resources and Wellness offices will assist in ensuring the sustainability of this workplace health initiative.
- Full Text:
- Date Issued: 2017
- Authors: Chigumete, Tinatsei Gabriella
- Date: 2017
- Subjects: Rhodes University -- Employees -- Health and hygiene , Employee health promotion -- South Africa -- Makhanda
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44509 , vital:25414
- Description: Background: Non-communicable diseases are rapidly advancing as leading causes of morbidity and mortality across social classes, exerting pressure on existing financial, organizational, and human resources. Health promotion is a common practice in the prevention of noncommunicable diseases, but workplace health promotion has not yet been well established in many workplaces. Identification of past workplace initiatives and exploring their facilitating and limiting factors is thus important to take into consideration when planning future initiatives. Well-informed and guided workplace health promotion initiatives are essential to improve the general health of staff, and these also need to take the broader cultural, socioeconomic, and environmental factors influencing non-communicable diseases in the target population into account. This two-phase study was conducted at Rhodes University. A needs assessment was conducted to identify current policies and practices of workplace health promotion and to identify any shortcomings of the initiatives that have previously been attempted to raise awareness of non-communicable diseases at Rhodes University. The second phase of this project aimed to address concerns raised in the first phase through a health promotion initiative for support staff that focuses on the prevention of noncommunicable diseases through heart healthy diets and physical activity. Method: The first phase of the current study involved working with the support staff and key stakeholders. Using the participatory action research approach and the PRECEDE-PROCEED model to guide the research, 11 semi-structured interviews with key stakeholders and 10 focus group discussions were conducted with support staff members to identify factors affecting workplace health promotion. Participant opinions on how to improve these initiatives were sought. The participants were asked to identify areas on which the intended intervention should focus, as well as to identify their preferred means of communicating health messages. During this phase, a group of support staff members who volunteered their involvement in the design and delivery of the educational intervention was also identified. They chose to go by the name, the Health Awareness Group.In an interim phase of the study, three health information leaflets informed by the results from the above activities were designed. These leaflets underwent a series of qualitative evaluations by other health professionals, a culture and African languages expert, and the Health Awareness Group, to assess content validity, context specificity, and cultural appropriateness for the target group. A series of quantitative tests for readability, suitability, and actionability was also conducted. The health information leaflets were then used as written materials in the educational intervention of the project. Members of the Health Awareness Group were also trained as peer educators through a series of workshops. This enabled them to promote and raise awareness of heart healthy diets and physical activity to others in the workplace. Workshops were participatory in nature and were guided by the Social Cognitive Theory. They were also equipped with the completed health information leaflets to distribute to their peers and to use as reference sources of information when needed. Results: Participants in the semi-structured interviews reported that some health promotion initiatives have previously been attempted and advertised to support staff, but the turnout was poor and most staff did not seem to understand the health benefits of these initiatives. The support staff, in turn, stated that most health talks were conducted in English, contained medical jargon, and that they would have preferred these initiatives either to be simplified or presented in their home language, and to display cultural sensitivity. Support staff have also reported that advertisements were too cliche to elicit their interest. They also suggested incentivising initiatives for better participation. Another key suggestion was to facilitate these initiatives in the university departments they work or other convenient venues, rather than at central venues. It was also suggested that these initiatives be part of the work calendar, as they are often 'impromptu' and, as a result, staff members did not have enough notice to take time off work. Several staff members requested 're-runs of these initiatives because one-time show cases are often inadequate'. Colourful visual representations on posters or leaflets, short plays or films were also proposed as modes of delivering health information. During the design of the material to be used for this project's intended intervention, the health information leaflets were deemed readable, suitable, actionable, context-specific, and culturally appropriate. Workshops conducted during Phase 2 of the study proved to be valuable in training peer educators. Members of the Health Awareness Group also deemed the workshops useful, and reported their readiness to be agents of change in the workplace. Conclusions: Based on the input of key stakeholders and support staff, health promotion policies and protocols for non-communicable diseases have not yet been developed. Health promotion initiatives, especially for support staff, that address non-communicable diseases have previously been attempted at the university but were not well-received. Factors affecting workplace health promotion were identified. Knowledge of these factors was useful in designing and tailoring the written educational materials and the educational intervention to the needs of the support staff and to redress the deficiencies of previous initiatives. The health leaflets were deemed appropriate for use by the target population. They addressed pertinent information needs. The health information leaflets and workshops were useful in equipping the Health Awareness Group with knowledge on heart healthy diets and promotion of physical activity. Continued the involvement of representatives from the Human Resources and Wellness offices will assist in ensuring the sustainability of this workplace health initiative.
- Full Text:
- Date Issued: 2017
Photophysical studies of conjugates of upconversion nanoparticles with aluminium phthalocyanines
- Authors: Watkins, Zane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4964 , vital:20747
- Description: NaYF4 :Yb/Er/Gd upconversion nanoparticles (UCNP) were synthesised and their photoemission stabilised by embedding these nanoparticles in electrospun fibres. The photophysical behaviour of chloro aluminium tetrasulfo-phthalocyanine chloride (ClAlTSPc) was studied in the presence of UCNPs on mixing the two species in solution. The fluorescence lifetimes for UCNPs were shortened at 658 nm in the presence of ClAlTSPc when the former was embedded in fibre and suspended in a dimethyl sulfoxide solution of the latter. A clear singlet oxygen generation by ClAlTSPc through Forster resonance energy transfer (FRET) was demonstrated using a singlet oxygen quencher, 1,3-diphenylisobenzofuran. UCNP capped with amino groups were then covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). There was a decrease in fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to FRET. Low FRET efficiencies of 18 and 21 % for ClAlTSPc and ClAlTCPc, respectively, were obtained.
- Full Text:
- Date Issued: 2017
- Authors: Watkins, Zane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4964 , vital:20747
- Description: NaYF4 :Yb/Er/Gd upconversion nanoparticles (UCNP) were synthesised and their photoemission stabilised by embedding these nanoparticles in electrospun fibres. The photophysical behaviour of chloro aluminium tetrasulfo-phthalocyanine chloride (ClAlTSPc) was studied in the presence of UCNPs on mixing the two species in solution. The fluorescence lifetimes for UCNPs were shortened at 658 nm in the presence of ClAlTSPc when the former was embedded in fibre and suspended in a dimethyl sulfoxide solution of the latter. A clear singlet oxygen generation by ClAlTSPc through Forster resonance energy transfer (FRET) was demonstrated using a singlet oxygen quencher, 1,3-diphenylisobenzofuran. UCNP capped with amino groups were then covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). There was a decrease in fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to FRET. Low FRET efficiencies of 18 and 21 % for ClAlTSPc and ClAlTCPc, respectively, were obtained.
- Full Text:
- Date Issued: 2017
The effect of point of substitution and silver based nanoparticles on the photophysical and optical nonlinearity of indium carboxyphenoxy phthalocyanine
- Oluwole, David O, Ngxeke, Sixolisile M, Britton, Jonathan, Nyokong, Tebello
- Authors: Oluwole, David O , Ngxeke, Sixolisile M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188596 , vital:44768 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.07.032"
- Description: Indium(III) chloride 1,8(11),15(18),22(25)-tetra-(3-carboxyphenoxy) phthalocyanine (1) and indium(III) chloride 2,9(10),16(17),23(24)-tetra–(3-carboxyphenoxy) phthalocyanine (2) were covalently linked to glutathione capped silver nanoparticles (AgNPs–GSH) and silver selenide/zinc sulfide (Ag2Se/ZnS–GSH) quantum dots via amide bond formation. The photophysical and nonlinear optical behaviour of the metallophthalocyanines and their conjugates with nanoparticles were investigated using the open aperture Z–scan technique. Complex 2 showed enhanced photophysical properties compared to 1. The conjugates revealed improved triplet state quantum yields (except for 1-AgNPs-GSH which afforded lower triplet state quantum yields in comparison to 1) and nonlinear optical activities in comparison to the Pc complexes. The synthesized complexes, nanoparticles and their conjugates could be potential nonlinear optical materials due to their good nonlinear optical activities.
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, David O , Ngxeke, Sixolisile M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188596 , vital:44768 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.07.032"
- Description: Indium(III) chloride 1,8(11),15(18),22(25)-tetra-(3-carboxyphenoxy) phthalocyanine (1) and indium(III) chloride 2,9(10),16(17),23(24)-tetra–(3-carboxyphenoxy) phthalocyanine (2) were covalently linked to glutathione capped silver nanoparticles (AgNPs–GSH) and silver selenide/zinc sulfide (Ag2Se/ZnS–GSH) quantum dots via amide bond formation. The photophysical and nonlinear optical behaviour of the metallophthalocyanines and their conjugates with nanoparticles were investigated using the open aperture Z–scan technique. Complex 2 showed enhanced photophysical properties compared to 1. The conjugates revealed improved triplet state quantum yields (except for 1-AgNPs-GSH which afforded lower triplet state quantum yields in comparison to 1) and nonlinear optical activities in comparison to the Pc complexes. The synthesized complexes, nanoparticles and their conjugates could be potential nonlinear optical materials due to their good nonlinear optical activities.
- Full Text:
- Date Issued: 2017
Development and assessment of ketoconazole intravaginal thermosetting hydrogel formulations
- Authors: Ramanah, Ashmita
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5198 , vital:20785
- Description: Imidazole compounds are commonly used as antifungal therapies and ketoconazole was the first broad spectrum orally active azole identified and registered. However, the risks of hepatotoxicity and drug interactions following systemic delivery and absorption of ketoconazole outweigh the therapeutic benefits and ketoconazole was therefore discontinued as first line systemic antifungal therapy in many countries. Although not yet banned in South Africa, the South African Medicine Formulary has ceased to recommend the use of ketoconazole for systemic treatment. Topical use of ketoconazole is, however, regarded as safe following extensive human use as low systemic absorption occurs following topical administration. Vulvo-vaginal candidiasis is a yeast infection that affects a large number of women, some of whom present with several infections annually. The topical treatment options for vulvo-vaginal candidiasis include the use of vaginal tablets, capsules, ovules and creams administered as a single dose or one to three times daily for three to fourteen days either alone or in combination with another dosage form depending on the regimen. Administration of the dose nightly is recommended for most vaginal creams and ovule formulation due to leakage and the uncomfortable feel of the dosage form if administered during the day. A thermosetting gel that remains in the vagina following administration and prolongs the release of ketoconazole from a once daily dose would be a useful addition to the arsenal for intra-vaginal antifungal therapy. Thermosetting gels would be more comfortable to administer as the gel would set in a form similar to naturally occurring mucous in the vagina and, if formulated with a low pH, irritation of the sensitive and fissured tissue would be minimised. A further benefit would be that once set the gel would loosely take on the anatomical shape of the vagina. A simple, precise, accurate, reproducible and sensitive stability-indicating reversed phase-high performance liquid chromatographic method using ultraviolet detection for the quantitation of ketoconazole was developed and validated. The method was specific and was applied to the determination of ketoconazole in commercial and experimental formulations in addition to samples from degradation studies and in vitro release testing. Product performance characteristics of commercial products were investigated with the goal to provide a strategy for the development of a novel intra vaginal gel in the shortest possible time. Characterisation of Xolegel®, Kez® shampoo and Ketazol® cream included an evaluation of pH, viscosity and assay, in addition to spectroscopic and thermal analysis, to identify ideal characteristics of topical products that could be used as targets during formulation development of the gel. An in vitro release method was developed and validated for precision and accuracy and the in vitro release profiles of commercial ketoconazole products were compared using analysis of variance, model dependent and independent approaches. Ketoconazole release data from test gel manufactured during formulation development were investigated to obtain information about the relationship between formulation content and drug release. Poloxamers marketed as Pluronic® and Lutrol® are synthetic non-ionic tri-block copolymers that consist of hydrophobic propylene oxide and hydrophilic polyethylene oxide blocks, which in solution interact to exhibit thermo-reversible behaviour. In situ forming hydrogels consisting of poloxamers, more specifically poloxamer 407, are activated following a temperature stimulus and undergo a sol to gel transition. This approach was used to produce a thermosetting vaginal gel that would exhibit a long residence time in the vagina with an associated enhancement of therapeutic efficacy. Ketoconazole- excipient compatibility was investigated during preformulation studies using spectroscopic and thermal analysis to enable the selection of excipients best suited for the production of a novel dosage form prior to formulation development activities. No obvious interactions between ketoconazole and excipient were observed and ketoconazole was found in an amorphous form when in combination with polysorbate 80 and poloxamers. A two-level factorial design was used to produce solvent systems with different amounts of polysorbate 80, citric acid and ethanol to identify a vehicle in which ketoconazole exhibited optimum solubility and at a pH that would be least irritating to the vaginal mucosa with a low content of excipients. The optimised vehicle consisted of 4% m/v citric acid, 1.5% v/v polysorbate 80 and 9.5% v/v ethanol made up to 50 g with citrate-phosphate buffer adjusted to pH 5.0, resulted in a vehicle of pH of 3.5 in which 71.41 mg of ketoconazole was dissolved per mL. A Central Composite Design was used to evaluate compositions for the modulation of viscosity of the thermosetting dosage form such that it was a liquid at 22 °C that rapidly formed a stiff gel when heated to 37 °C (intra-vaginal temperature) using different amounts of the poloxamer grades 407, 188 and 237. Thermosetting gels containing 2% m/v ketoconazole were manufactured using specifications generated using the Central Composite Design and the viscosity at 22 °C and 37 °C, solution to gel transition time, potency and ketoconazole release at 24, 48 and 72 hours investigated. Contour and three-dimensional response surface plots and mathematical relationships with target ranges set for responses were identified and with the aid of Central Composite Design the optimisation of a desirable thermosetting gel was achieved. The optimised composition included 16% m/v poloxamer 407, 10% m/v poloxamer 188 and 6% m/v poloxamer 237 in the gel that was used as the basis for further optimisation studies. The low ketoconazole release for ketoconazole observed indicated that the poloxamers had formed a gel matrix that sustained the release of ketoconazole and would therefore ensure that once daily administration of the gel was possible. The sol-gel transition test may be used as a simple and cheap alternative to viscosity testing for thermosetting formulations when expensive viscometers and rheometers are unavailable and was successfully used for this purpose.Ketoconazole is photolabile and is prone to degradation in aqueous solutions. The hydrophobic core of micelles formed in these dosage forms are believed to shield ketoconazole molecules and improve stability in aqueous solutions and acidic gels. The thermosetting gel optimised for poloxamer content was subjected to a further Central Composite Design in which sodium metabisulphite content and vehicle pH were investigated. The length of storage was used as a numeric variable and storage condition as a categoric variable at two levels to monitor the stability of the gels. The formulations were investigated at sample times of 0, 1, 2, 4 and 8 weeks at 5 °C, 25 °C and 40 °C. The use of a Central Composite Design facilitated an understanding of the interactions between input variables and their impact on the responses analysed including ketoconazole content, release at 24, 48 and 72 hours, gel pH and viscosity at 22 °C and 37 °C. Design of Experiments may be used as a rapid cost effective tool for an overall assessment of the stability of novel topical dosage forms. However, a more thorough assessment of stability may be required for product registration. Ketoconazole was found to be unstable in the acidic thermosetting gels despite the addition of antioxidant. The gels in liquid form at 5 °C and 25 °C have a low number of micelles for ketoconazole incorporation and therefore additional optimisation studies would be required to enhance the shelf-life of this product.
- Full Text:
- Date Issued: 2017
- Authors: Ramanah, Ashmita
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/5198 , vital:20785
- Description: Imidazole compounds are commonly used as antifungal therapies and ketoconazole was the first broad spectrum orally active azole identified and registered. However, the risks of hepatotoxicity and drug interactions following systemic delivery and absorption of ketoconazole outweigh the therapeutic benefits and ketoconazole was therefore discontinued as first line systemic antifungal therapy in many countries. Although not yet banned in South Africa, the South African Medicine Formulary has ceased to recommend the use of ketoconazole for systemic treatment. Topical use of ketoconazole is, however, regarded as safe following extensive human use as low systemic absorption occurs following topical administration. Vulvo-vaginal candidiasis is a yeast infection that affects a large number of women, some of whom present with several infections annually. The topical treatment options for vulvo-vaginal candidiasis include the use of vaginal tablets, capsules, ovules and creams administered as a single dose or one to three times daily for three to fourteen days either alone or in combination with another dosage form depending on the regimen. Administration of the dose nightly is recommended for most vaginal creams and ovule formulation due to leakage and the uncomfortable feel of the dosage form if administered during the day. A thermosetting gel that remains in the vagina following administration and prolongs the release of ketoconazole from a once daily dose would be a useful addition to the arsenal for intra-vaginal antifungal therapy. Thermosetting gels would be more comfortable to administer as the gel would set in a form similar to naturally occurring mucous in the vagina and, if formulated with a low pH, irritation of the sensitive and fissured tissue would be minimised. A further benefit would be that once set the gel would loosely take on the anatomical shape of the vagina. A simple, precise, accurate, reproducible and sensitive stability-indicating reversed phase-high performance liquid chromatographic method using ultraviolet detection for the quantitation of ketoconazole was developed and validated. The method was specific and was applied to the determination of ketoconazole in commercial and experimental formulations in addition to samples from degradation studies and in vitro release testing. Product performance characteristics of commercial products were investigated with the goal to provide a strategy for the development of a novel intra vaginal gel in the shortest possible time. Characterisation of Xolegel®, Kez® shampoo and Ketazol® cream included an evaluation of pH, viscosity and assay, in addition to spectroscopic and thermal analysis, to identify ideal characteristics of topical products that could be used as targets during formulation development of the gel. An in vitro release method was developed and validated for precision and accuracy and the in vitro release profiles of commercial ketoconazole products were compared using analysis of variance, model dependent and independent approaches. Ketoconazole release data from test gel manufactured during formulation development were investigated to obtain information about the relationship between formulation content and drug release. Poloxamers marketed as Pluronic® and Lutrol® are synthetic non-ionic tri-block copolymers that consist of hydrophobic propylene oxide and hydrophilic polyethylene oxide blocks, which in solution interact to exhibit thermo-reversible behaviour. In situ forming hydrogels consisting of poloxamers, more specifically poloxamer 407, are activated following a temperature stimulus and undergo a sol to gel transition. This approach was used to produce a thermosetting vaginal gel that would exhibit a long residence time in the vagina with an associated enhancement of therapeutic efficacy. Ketoconazole- excipient compatibility was investigated during preformulation studies using spectroscopic and thermal analysis to enable the selection of excipients best suited for the production of a novel dosage form prior to formulation development activities. No obvious interactions between ketoconazole and excipient were observed and ketoconazole was found in an amorphous form when in combination with polysorbate 80 and poloxamers. A two-level factorial design was used to produce solvent systems with different amounts of polysorbate 80, citric acid and ethanol to identify a vehicle in which ketoconazole exhibited optimum solubility and at a pH that would be least irritating to the vaginal mucosa with a low content of excipients. The optimised vehicle consisted of 4% m/v citric acid, 1.5% v/v polysorbate 80 and 9.5% v/v ethanol made up to 50 g with citrate-phosphate buffer adjusted to pH 5.0, resulted in a vehicle of pH of 3.5 in which 71.41 mg of ketoconazole was dissolved per mL. A Central Composite Design was used to evaluate compositions for the modulation of viscosity of the thermosetting dosage form such that it was a liquid at 22 °C that rapidly formed a stiff gel when heated to 37 °C (intra-vaginal temperature) using different amounts of the poloxamer grades 407, 188 and 237. Thermosetting gels containing 2% m/v ketoconazole were manufactured using specifications generated using the Central Composite Design and the viscosity at 22 °C and 37 °C, solution to gel transition time, potency and ketoconazole release at 24, 48 and 72 hours investigated. Contour and three-dimensional response surface plots and mathematical relationships with target ranges set for responses were identified and with the aid of Central Composite Design the optimisation of a desirable thermosetting gel was achieved. The optimised composition included 16% m/v poloxamer 407, 10% m/v poloxamer 188 and 6% m/v poloxamer 237 in the gel that was used as the basis for further optimisation studies. The low ketoconazole release for ketoconazole observed indicated that the poloxamers had formed a gel matrix that sustained the release of ketoconazole and would therefore ensure that once daily administration of the gel was possible. The sol-gel transition test may be used as a simple and cheap alternative to viscosity testing for thermosetting formulations when expensive viscometers and rheometers are unavailable and was successfully used for this purpose.Ketoconazole is photolabile and is prone to degradation in aqueous solutions. The hydrophobic core of micelles formed in these dosage forms are believed to shield ketoconazole molecules and improve stability in aqueous solutions and acidic gels. The thermosetting gel optimised for poloxamer content was subjected to a further Central Composite Design in which sodium metabisulphite content and vehicle pH were investigated. The length of storage was used as a numeric variable and storage condition as a categoric variable at two levels to monitor the stability of the gels. The formulations were investigated at sample times of 0, 1, 2, 4 and 8 weeks at 5 °C, 25 °C and 40 °C. The use of a Central Composite Design facilitated an understanding of the interactions between input variables and their impact on the responses analysed including ketoconazole content, release at 24, 48 and 72 hours, gel pH and viscosity at 22 °C and 37 °C. Design of Experiments may be used as a rapid cost effective tool for an overall assessment of the stability of novel topical dosage forms. However, a more thorough assessment of stability may be required for product registration. Ketoconazole was found to be unstable in the acidic thermosetting gels despite the addition of antioxidant. The gels in liquid form at 5 °C and 25 °C have a low number of micelles for ketoconazole incorporation and therefore additional optimisation studies would be required to enhance the shelf-life of this product.
- Full Text:
- Date Issued: 2017
A comparative study of the dosimetric features of α-Al2O3: C, Mg and α-Al2O3: C
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113058 , vital:33694 , https://doi.org/10.1093/rpd/ncx039
- Description: A comparative study of the dosimetric features of α-Al2O3:C,Mg and α-Al2O3:C relevant to thermoluminescence dosimetry is reported. A glow curve of α-Al2O3:C,Mg measured at 1°C/s after beta irradiation to 1 Gy shows two subsidiary peaks at 42°C (labelled as I) and 72°C (II) and the main peak at 161°C (III) whereas a glow curve of α-Al2O3:C measured under the same conditions shows the main peak at 178°C (II′) and a lower intensity peak at 48°C (I′). Apart from these ones, there are several other peaks at temperatures beyond that of the main peak in both α-Al2O3:C,Mg and α-Al2O3:C. However, the latter are not included in this study. We report a comparative quantitative analysis of dose response and fading of peaks I, II and III of α-Al2O3:C,Mg and peaks I′ and II′ of α-Al2O3:C. Analysis shows that the dose response of peaks I and III is sublinear within 1–10 Gy whereas that of peak II is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy. In comparison, the dose response of peak I′ is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy whereas that of peak II′ is sublinear within 1–4 Gy followed by a superlinear region within 4–10 Gy. As regards to fading corresponding to 1 Gy, peak I is very unstable and fades within 300 s, peak II is more stable and takes up to 43200 s to fade. In comparison, peak III fades down to 30% of its initial intensity within 2400 s. Interestingly, between 2400 and 800 s, the intensity fades by 17% only. Regarding fading in α-Al2O3:C, peak I′ fades within 600 s whereas peak II′ shows an inverse fading behaviour up to 64800 s. The rate of fading for peaks I, II and III in α-Al2O3:C,Mg was found to decrease with increase in dose. However, no such behaviour was observed in α-Al2O3:C. The fading in both samples is discussed on the basis of a charge hopping mechanism.
- Full Text:
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113058 , vital:33694 , https://doi.org/10.1093/rpd/ncx039
- Description: A comparative study of the dosimetric features of α-Al2O3:C,Mg and α-Al2O3:C relevant to thermoluminescence dosimetry is reported. A glow curve of α-Al2O3:C,Mg measured at 1°C/s after beta irradiation to 1 Gy shows two subsidiary peaks at 42°C (labelled as I) and 72°C (II) and the main peak at 161°C (III) whereas a glow curve of α-Al2O3:C measured under the same conditions shows the main peak at 178°C (II′) and a lower intensity peak at 48°C (I′). Apart from these ones, there are several other peaks at temperatures beyond that of the main peak in both α-Al2O3:C,Mg and α-Al2O3:C. However, the latter are not included in this study. We report a comparative quantitative analysis of dose response and fading of peaks I, II and III of α-Al2O3:C,Mg and peaks I′ and II′ of α-Al2O3:C. Analysis shows that the dose response of peaks I and III is sublinear within 1–10 Gy whereas that of peak II is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy. In comparison, the dose response of peak I′ is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy whereas that of peak II′ is sublinear within 1–4 Gy followed by a superlinear region within 4–10 Gy. As regards to fading corresponding to 1 Gy, peak I is very unstable and fades within 300 s, peak II is more stable and takes up to 43200 s to fade. In comparison, peak III fades down to 30% of its initial intensity within 2400 s. Interestingly, between 2400 and 800 s, the intensity fades by 17% only. Regarding fading in α-Al2O3:C, peak I′ fades within 600 s whereas peak II′ shows an inverse fading behaviour up to 64800 s. The rate of fading for peaks I, II and III in α-Al2O3:C,Mg was found to decrease with increase in dose. However, no such behaviour was observed in α-Al2O3:C. The fading in both samples is discussed on the basis of a charge hopping mechanism.
- Full Text:
- Date Issued: 2017
Exploring the influence of a multiliteracies approach on Grade 11 Physical Sciences learners' sense making and dispositions towards graphs of motion
- Authors: Mwiiyale, Laina Natangwe
- Date: 2017
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/17605 , vital:22264
- Description: Namibian students perform poorly in Physical Sciences and the Physics component in particular (DNEA, 2013). The Namibian Senior Secondary Certificate (NSSC) Examiner's report (DNEA, 2014) also reveals that many Physical Science learners have difficulties demonstrating an understanding of basic physics required for working with kinematic graphs (graphical representation of motion). Kinematics is an important tool in understanding the motion of objects - whether translational, oscillatory or circular. In kinematics, the relationships between distance, displacement, speed, velocity or acceleration and time are represented in graphs of motion. In teaching the topic, using graphs can be an alternative to the use of abstract formulas, or formulas can be used along with graphical representations to facilitate student understanding (Behzak, 2006). This study explored the influence of the multiliteracies approach on grade 11 Physical Science learners' dispositions and sense making towards graphs of motion. The intervention being investigated is informed by the Pedagogy of Multiliteracies (PoM) framework by Cazden et al., (1996) with the focus on overt instruction, situated practice, critical framing and transformed practice using semiotic patterns of meaning, in conjunction with Vygotsky's (1978) social constructivism theory - particularly, its notion of mediation. This action research study employed the interpretive paradigm. Data were collected using a pre-test, stimulated recall interviews, lesson observations, a post-test and learners' reflections. Data were coded and the codes then categorized into different themes in order to answer the research questions. The findings of this study were that learners are better able to make sense of graphs of motions when a PoM approach is employed. Their dispositions towards graphs of motion also improved as a result of the PoM intervention, due to it enabling a better understanding of kinematics concepts. This study also contributed to the professional development of the researcher, particularly in terms of it contributing to a broader understanding of the research and possible usefulness of semiotic mediation in science education. Implications of the study include the possibility of including the PoM approach in science teacher education and training programme curricula.
- Full Text:
- Date Issued: 2017
- Authors: Mwiiyale, Laina Natangwe
- Date: 2017
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/17605 , vital:22264
- Description: Namibian students perform poorly in Physical Sciences and the Physics component in particular (DNEA, 2013). The Namibian Senior Secondary Certificate (NSSC) Examiner's report (DNEA, 2014) also reveals that many Physical Science learners have difficulties demonstrating an understanding of basic physics required for working with kinematic graphs (graphical representation of motion). Kinematics is an important tool in understanding the motion of objects - whether translational, oscillatory or circular. In kinematics, the relationships between distance, displacement, speed, velocity or acceleration and time are represented in graphs of motion. In teaching the topic, using graphs can be an alternative to the use of abstract formulas, or formulas can be used along with graphical representations to facilitate student understanding (Behzak, 2006). This study explored the influence of the multiliteracies approach on grade 11 Physical Science learners' dispositions and sense making towards graphs of motion. The intervention being investigated is informed by the Pedagogy of Multiliteracies (PoM) framework by Cazden et al., (1996) with the focus on overt instruction, situated practice, critical framing and transformed practice using semiotic patterns of meaning, in conjunction with Vygotsky's (1978) social constructivism theory - particularly, its notion of mediation. This action research study employed the interpretive paradigm. Data were collected using a pre-test, stimulated recall interviews, lesson observations, a post-test and learners' reflections. Data were coded and the codes then categorized into different themes in order to answer the research questions. The findings of this study were that learners are better able to make sense of graphs of motions when a PoM approach is employed. Their dispositions towards graphs of motion also improved as a result of the PoM intervention, due to it enabling a better understanding of kinematics concepts. This study also contributed to the professional development of the researcher, particularly in terms of it contributing to a broader understanding of the research and possible usefulness of semiotic mediation in science education. Implications of the study include the possibility of including the PoM approach in science teacher education and training programme curricula.
- Full Text:
- Date Issued: 2017
Devulcanization of model compounds by a variety of diphenyldisulfides
- Authors: Boyce, Annemè
- Date: 2017
- Subjects: Rubber -- Recycling Rubber, Reclaimed , Rubber -- Standards -- South Africa Rubber -- Research Chromatographic analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14730 , vital:27834
- Description: Improvements to the properties of recycled rubber, by developing a more selective breakdown process, is an important issue and a global challenge. Devulcanization is the most promising way to achieve this. It is a process which aims to totally or partially cleave monosulfidic (C-S-C), disulfidic (C-S-S-C) and polysulfidic (C-Sx-C) crosslinks of vulcanized rubber. In this study, the devulcanization of sulfur-vulcanized natural rubber with a variety of diphenyldisulfides has been studied using 2,3-dimethyl-2-butene and squalene as model compounds, vulcanized by sulfur and 2-bisbenzothiazole-2,2’-disulfide. 2-aminodiphenyldisulfide; 4-amino-diphenyldisulfide; bis(2-benzamido-)diphenyldisulfide and 2,2’-bithiosalicylic acid were used as aromatic disulfides devulcanization agents. Thermal analysis was used to investigate interactions between various combinations of curatives in the vulcanization systems in the absence of model compounds. Thermogravimetric analysis was used to detect mass changes during vulcanization and whether the samples decompose/evaporate so as not to contaminate differential scanning calorimetry instrumentation. Differential scanning calorimetry was used to investigate reactions occurring between curatives. Comparison of reversing and non-reversing signals in modulated experiments are suggestive of reactions between devulcanization agents and sulfur, and accelerators Vulcanization of the model compounds were performed in 10m evacuated sealed glass ampoules placed in an oil bath at 160 °C and agitated for the duration of vulcanization. After 60 min the ampoules were removed and quenched. These were then devulcanized by exposure to a devulcanization agent in a sealed ampoule at 180 for 60 min. Crosslinked 2,3-dimethyl-2-butene species were isolated and analysed by reversed phase high performance liquid chromatography. Particular attention was paid to changes in the number of sulfur atoms in the crosslinks. Results indicate that of the devulcanization agents tested 4-amino-diphenyldisulfide was the most effective. No detrimental effect on devulcanization efficiency was caused by the substitution of a basic amino group with an acidic carboxylic acid group Gel permeation chromatography was performed on devulcanized squalene crosslinks using a tetrahydrofuran eluent. GPC investigations with squalene were less effective than HPLC experiments with 2,3-dimethyl-2-butene at evaluating the relative efficiency of individual devulcanization agents. Results were, however, consistent with 4-amino-diphenyldisulfide again being the most efficient devulcanization agent.
- Full Text:
- Date Issued: 2017
- Authors: Boyce, Annemè
- Date: 2017
- Subjects: Rubber -- Recycling Rubber, Reclaimed , Rubber -- Standards -- South Africa Rubber -- Research Chromatographic analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14730 , vital:27834
- Description: Improvements to the properties of recycled rubber, by developing a more selective breakdown process, is an important issue and a global challenge. Devulcanization is the most promising way to achieve this. It is a process which aims to totally or partially cleave monosulfidic (C-S-C), disulfidic (C-S-S-C) and polysulfidic (C-Sx-C) crosslinks of vulcanized rubber. In this study, the devulcanization of sulfur-vulcanized natural rubber with a variety of diphenyldisulfides has been studied using 2,3-dimethyl-2-butene and squalene as model compounds, vulcanized by sulfur and 2-bisbenzothiazole-2,2’-disulfide. 2-aminodiphenyldisulfide; 4-amino-diphenyldisulfide; bis(2-benzamido-)diphenyldisulfide and 2,2’-bithiosalicylic acid were used as aromatic disulfides devulcanization agents. Thermal analysis was used to investigate interactions between various combinations of curatives in the vulcanization systems in the absence of model compounds. Thermogravimetric analysis was used to detect mass changes during vulcanization and whether the samples decompose/evaporate so as not to contaminate differential scanning calorimetry instrumentation. Differential scanning calorimetry was used to investigate reactions occurring between curatives. Comparison of reversing and non-reversing signals in modulated experiments are suggestive of reactions between devulcanization agents and sulfur, and accelerators Vulcanization of the model compounds were performed in 10m evacuated sealed glass ampoules placed in an oil bath at 160 °C and agitated for the duration of vulcanization. After 60 min the ampoules were removed and quenched. These were then devulcanized by exposure to a devulcanization agent in a sealed ampoule at 180 for 60 min. Crosslinked 2,3-dimethyl-2-butene species were isolated and analysed by reversed phase high performance liquid chromatography. Particular attention was paid to changes in the number of sulfur atoms in the crosslinks. Results indicate that of the devulcanization agents tested 4-amino-diphenyldisulfide was the most effective. No detrimental effect on devulcanization efficiency was caused by the substitution of a basic amino group with an acidic carboxylic acid group Gel permeation chromatography was performed on devulcanized squalene crosslinks using a tetrahydrofuran eluent. GPC investigations with squalene were less effective than HPLC experiments with 2,3-dimethyl-2-butene at evaluating the relative efficiency of individual devulcanization agents. Results were, however, consistent with 4-amino-diphenyldisulfide again being the most efficient devulcanization agent.
- Full Text:
- Date Issued: 2017
Synthesis and bioassay of rationally designed DXR inhibitors as potential antimalarial lead compounds
- Authors: Nokalipa, Iviwe Cwaita
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4888 , vital:20740
- Description: Globally, the eradication of malaria has been challenging due to the problem of resistance that past and currently available drugs exhibit. This is exacerbated by the inherent need for anti-malarial drugs to be affordable to the poverty-stricken majority that is primarily affected by this burden. This research has focused on the development of potential inhibitors of 1-deoxy-D- xylulose-5 phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate- independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate into 2-C- methyl-D-erithrytol 4-phosphate. This enzyme has been determined to be a target for the development of novel antimalarial agents and extensive molecular modelling has been undertaken to develop inhibitors that fit into the DXR active site. The in silico docking data have been used to inform the design and synthesis of various N-benzyl-substituted phosphoramidate ligands that were determined to have potential as novel substrate mimics of fosmidomycin, a known DXR inhibitor. Synthesis of the N-benzyl-substituted phosphoramidate ligands involved a nine-step sequence commencing from diethyl phosphoramidate. In all, some 40 compounds have been prepared, some of them new, and were fully characterized using NMR. Attention has also been given to the mass spectrometric fragmentation patterns exhibited by selected intermediates. Four of the final products were evaluated for in vitro antimalarial activity using a PLDH assay and exhibited IC50 values < 100 µM.
- Full Text:
- Date Issued: 2017
- Authors: Nokalipa, Iviwe Cwaita
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4888 , vital:20740
- Description: Globally, the eradication of malaria has been challenging due to the problem of resistance that past and currently available drugs exhibit. This is exacerbated by the inherent need for anti-malarial drugs to be affordable to the poverty-stricken majority that is primarily affected by this burden. This research has focused on the development of potential inhibitors of 1-deoxy-D- xylulose-5 phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate- independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate into 2-C- methyl-D-erithrytol 4-phosphate. This enzyme has been determined to be a target for the development of novel antimalarial agents and extensive molecular modelling has been undertaken to develop inhibitors that fit into the DXR active site. The in silico docking data have been used to inform the design and synthesis of various N-benzyl-substituted phosphoramidate ligands that were determined to have potential as novel substrate mimics of fosmidomycin, a known DXR inhibitor. Synthesis of the N-benzyl-substituted phosphoramidate ligands involved a nine-step sequence commencing from diethyl phosphoramidate. In all, some 40 compounds have been prepared, some of them new, and were fully characterized using NMR. Attention has also been given to the mass spectrometric fragmentation patterns exhibited by selected intermediates. Four of the final products were evaluated for in vitro antimalarial activity using a PLDH assay and exhibited IC50 values < 100 µM.
- Full Text:
- Date Issued: 2017
Characterisation, antimalarial and biological activities of secondary metabolites from leaves of anonidium mannii
- Authors: Makoni, Pfungwa Gervase
- Date: 2017
- Subjects: Anonidium mannii -- Therapeutic use , Botanical chemistry , Annonaceae -- Therapeutic use , Apocynaceae -- Therapeutic use , Malaria -- Chemotherapy , Tuberculosis -- Chemotherapy , Bacterial diseases -- Chemotherapy , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4797 , vital:20725
- Description: Anonidium mannii is a plant of the Annonaceae genus which is used traditionally in Africa for the treatment of gonorrhoea, malaria, cancer, skin inflammation and dysentery. In this study we will evaluate antimalarial, antifungal, anti - tuberculosis, antibacterial activities and cytotoxicity of different fractions in order to provide a scientific rationale for the traditional use of Anonidium mannii as well as provide possible novel drugs in the treatment of multi drug resistant strains of parasites and bacteria. Extracts from dried leaves were obtained by using solvent extraction and different fractions obtained using column chromatography eluted with solvents of varying polarities to obtain a wide range of metabolites. The antimalarial activity of the various fractions and some pure compounds was evaluated using plasmodium lactate dehydrogenase (pLDH) assay. Cytotoxicity was evaluated using HeLa cells while anti – tuberculosis assay was evaluated using the green fluorescent protein. Antibacterial activity of the extracts was evaluated using micro-dilution assay against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria and Gram-negative (Escherichia coli and Salmonella typhi) bacteria. Antifungal activity was evaluated against Candida albicans. The antimalarial assays yielded some fractions with promising IC50 values. The selected fractions yielded activities ranging between 0.73 μg/mL and 20.23 μg/mL. The fraction with the best activity was obtained from a hexane/ethyl acetate fraction. AM1C, a cholestane, showed the best activity from the pure metabolites that were screened. AM3C, stigmasterol, a pure compound gave the best antifungal activity with an MIC of 0.063 μg/mL. AM9C another pure compound (sterol) showed the best activity against S. typhi with a value of 0.031 μg/mL. AM2C a pure compound showed an activity of 0.063 μg/mL against E. faecalis. The best cytotoxicity was demonstrated by the fraction C2AM3P with a cell viability of 7.1 ± 0.2 % while AM1C had a viability of 20.2 ± 1.2 %. Several pure metabolites were isolated and four of these were positively identified as steroids. Of these steroids the structure of three novel metabolites from A. mannii was deduced. The study showed promising antibacterial, antifungal, anti – tuberculosis, antimalarial and anticancer activity of A. mannii. These results validate the use of A. manni against cancer, skin inflammation which is caused by fungus, malaria and bacterial diseases.
- Full Text:
- Date Issued: 2017
- Authors: Makoni, Pfungwa Gervase
- Date: 2017
- Subjects: Anonidium mannii -- Therapeutic use , Botanical chemistry , Annonaceae -- Therapeutic use , Apocynaceae -- Therapeutic use , Malaria -- Chemotherapy , Tuberculosis -- Chemotherapy , Bacterial diseases -- Chemotherapy , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4797 , vital:20725
- Description: Anonidium mannii is a plant of the Annonaceae genus which is used traditionally in Africa for the treatment of gonorrhoea, malaria, cancer, skin inflammation and dysentery. In this study we will evaluate antimalarial, antifungal, anti - tuberculosis, antibacterial activities and cytotoxicity of different fractions in order to provide a scientific rationale for the traditional use of Anonidium mannii as well as provide possible novel drugs in the treatment of multi drug resistant strains of parasites and bacteria. Extracts from dried leaves were obtained by using solvent extraction and different fractions obtained using column chromatography eluted with solvents of varying polarities to obtain a wide range of metabolites. The antimalarial activity of the various fractions and some pure compounds was evaluated using plasmodium lactate dehydrogenase (pLDH) assay. Cytotoxicity was evaluated using HeLa cells while anti – tuberculosis assay was evaluated using the green fluorescent protein. Antibacterial activity of the extracts was evaluated using micro-dilution assay against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria and Gram-negative (Escherichia coli and Salmonella typhi) bacteria. Antifungal activity was evaluated against Candida albicans. The antimalarial assays yielded some fractions with promising IC50 values. The selected fractions yielded activities ranging between 0.73 μg/mL and 20.23 μg/mL. The fraction with the best activity was obtained from a hexane/ethyl acetate fraction. AM1C, a cholestane, showed the best activity from the pure metabolites that were screened. AM3C, stigmasterol, a pure compound gave the best antifungal activity with an MIC of 0.063 μg/mL. AM9C another pure compound (sterol) showed the best activity against S. typhi with a value of 0.031 μg/mL. AM2C a pure compound showed an activity of 0.063 μg/mL against E. faecalis. The best cytotoxicity was demonstrated by the fraction C2AM3P with a cell viability of 7.1 ± 0.2 % while AM1C had a viability of 20.2 ± 1.2 %. Several pure metabolites were isolated and four of these were positively identified as steroids. Of these steroids the structure of three novel metabolites from A. mannii was deduced. The study showed promising antibacterial, antifungal, anti – tuberculosis, antimalarial and anticancer activity of A. mannii. These results validate the use of A. manni against cancer, skin inflammation which is caused by fungus, malaria and bacterial diseases.
- Full Text:
- Date Issued: 2017
Health promotion: approaches to dietary salt reduction
- Authors: Mushoriwa, Fadzai
- Date: 2017
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44761 , vital:25439
- Description: Background Globally, non-communicable diseases are the leading causes of mortality and morbidity, with the majority of these occurring in low-middle income countries. The devastating consequences of non-communicable diseases could be curtailed through better management of four modifiable factors: physical inactivity; tobacco use; harmful use of alcohol; and unhealthy diets. The World Health Organisation has recommended dietary salt reduction as a cost-effective strategy in combatting the burden of NCDs. Consumer awareness and education is one of three primary strategies that have been identified by the World Health Organisation to achieve population-wide salt reduction. It involves the provision of salt reduction knowledge and the promotion of healthy salt related practices. These campaigns are a necessity in populations with high discretionary salt use such as South Africa. For these health promotion activities to succeed, they need to be developed with consideration of factors such as the environment, culture, and socio-economic standing of the intended target population. This two-phase health promotion study was conducted at St Mary’s Development and Care Centre and the Assumption Sisters Nutrition Centre. These are two community based organisations located in Grahamstown, South Africa. A needs assessment was conducted to identify the knowledge and practices of cooks and guardians from these centres on dietary salt reduction. The aim of the second phase of the study was to conduct an educational intervention and to develop a culturally appropriate and contextually specific health information intervention through a participatory process. Method: This was a qualitative study that was supported by elements of quantitative research.. The first phase of the current study was a needs assessment. The first step involved an observational phase with cooks from the centres. The aim was to observe their discretionary salt use during food preparation and to document the salt content in the processed foods available at each centre. Semi-structured interviews were then conducted, with 3 cooks and 16 guardians1 from the centres, to assess their knowledge and practices regarding salt reduction.Parents or the people responsible for the care of the children attending both centres. Guided by findings from the needs assessment phase, an educational intervention was developed. This phase involved the participatory development of three health information leaflets and a series of educational interactive sessions were conducted. Quantitative tests to assess the readability, suitability, and actionability were conducted on the leaflets. Qualitative assessment of the leaflets involved formative evaluations conducted by health care professionals, phase 1 participants, Rhodes University peer educators, an African languages and cultural expert, and a Rhodes University student wellness manager. This step was included to assess the content validity, context specificity, acceptability, and cultural appropriateness of the materials. Educational interactive sessions were guided by constructs of the Social Cognitive Theory and were conducted on three main topics: ‘Salt and my health’, ‘Reducing salt in my diet’, and ‘Reading food labels’. Results: The majority of the processed foods available at both centres contained low to medium levels of salt. Children at the centres were not provided with salt shakers on the tables during meal times. Cooks did not use measuring utensils when adding salt during meal preparation. Semistructured interviews revealed that participants lacked both declarative and procedural knowledge. In terms of declarative knowledge, they were unaware of the daily salt intake recommendations and the relationship between salt and sodium. Participants were able to identify hypertension as one of the health related consequences of high salt consumption. Most participants were responsible for purchasing groceries in their households. Their selfreported food label reading behaviours and inability to read food labels highlighted their lack of procedural knowledge. Most participants reported that they added salt during meal preparation and at mealtimes, highlighting high discretionary salt use. Some participants were also aware of cultural or religious uses of salt. The developed health information leaflets were considered to be written at a readability level appropriate for the target audience. The leaflets were also deemed to be actionable, culturally appropriate, and contextually specific and suitable materials. The educational interactive sessions were found to be interesting and informative. Conclusions: Findings from the needs assessment revealed the need for an educational intervention to address the identified gaps in the participants’ knowledge and practices regarding dietary salt reduction. The developed health information leaflets were found to be informative, culturally appropriate, and contextually specific, as planned. Interactive sessions provided an excellent platform to supply participants with concise and accurate information, increasing the possibility of improving their salt reduction related knowledge.
- Full Text:
- Date Issued: 2017
- Authors: Mushoriwa, Fadzai
- Date: 2017
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44761 , vital:25439
- Description: Background Globally, non-communicable diseases are the leading causes of mortality and morbidity, with the majority of these occurring in low-middle income countries. The devastating consequences of non-communicable diseases could be curtailed through better management of four modifiable factors: physical inactivity; tobacco use; harmful use of alcohol; and unhealthy diets. The World Health Organisation has recommended dietary salt reduction as a cost-effective strategy in combatting the burden of NCDs. Consumer awareness and education is one of three primary strategies that have been identified by the World Health Organisation to achieve population-wide salt reduction. It involves the provision of salt reduction knowledge and the promotion of healthy salt related practices. These campaigns are a necessity in populations with high discretionary salt use such as South Africa. For these health promotion activities to succeed, they need to be developed with consideration of factors such as the environment, culture, and socio-economic standing of the intended target population. This two-phase health promotion study was conducted at St Mary’s Development and Care Centre and the Assumption Sisters Nutrition Centre. These are two community based organisations located in Grahamstown, South Africa. A needs assessment was conducted to identify the knowledge and practices of cooks and guardians from these centres on dietary salt reduction. The aim of the second phase of the study was to conduct an educational intervention and to develop a culturally appropriate and contextually specific health information intervention through a participatory process. Method: This was a qualitative study that was supported by elements of quantitative research.. The first phase of the current study was a needs assessment. The first step involved an observational phase with cooks from the centres. The aim was to observe their discretionary salt use during food preparation and to document the salt content in the processed foods available at each centre. Semi-structured interviews were then conducted, with 3 cooks and 16 guardians1 from the centres, to assess their knowledge and practices regarding salt reduction.Parents or the people responsible for the care of the children attending both centres. Guided by findings from the needs assessment phase, an educational intervention was developed. This phase involved the participatory development of three health information leaflets and a series of educational interactive sessions were conducted. Quantitative tests to assess the readability, suitability, and actionability were conducted on the leaflets. Qualitative assessment of the leaflets involved formative evaluations conducted by health care professionals, phase 1 participants, Rhodes University peer educators, an African languages and cultural expert, and a Rhodes University student wellness manager. This step was included to assess the content validity, context specificity, acceptability, and cultural appropriateness of the materials. Educational interactive sessions were guided by constructs of the Social Cognitive Theory and were conducted on three main topics: ‘Salt and my health’, ‘Reducing salt in my diet’, and ‘Reading food labels’. Results: The majority of the processed foods available at both centres contained low to medium levels of salt. Children at the centres were not provided with salt shakers on the tables during meal times. Cooks did not use measuring utensils when adding salt during meal preparation. Semistructured interviews revealed that participants lacked both declarative and procedural knowledge. In terms of declarative knowledge, they were unaware of the daily salt intake recommendations and the relationship between salt and sodium. Participants were able to identify hypertension as one of the health related consequences of high salt consumption. Most participants were responsible for purchasing groceries in their households. Their selfreported food label reading behaviours and inability to read food labels highlighted their lack of procedural knowledge. Most participants reported that they added salt during meal preparation and at mealtimes, highlighting high discretionary salt use. Some participants were also aware of cultural or religious uses of salt. The developed health information leaflets were considered to be written at a readability level appropriate for the target audience. The leaflets were also deemed to be actionable, culturally appropriate, and contextually specific and suitable materials. The educational interactive sessions were found to be interesting and informative. Conclusions: Findings from the needs assessment revealed the need for an educational intervention to address the identified gaps in the participants’ knowledge and practices regarding dietary salt reduction. The developed health information leaflets were found to be informative, culturally appropriate, and contextually specific, as planned. Interactive sessions provided an excellent platform to supply participants with concise and accurate information, increasing the possibility of improving their salt reduction related knowledge.
- Full Text:
- Date Issued: 2017
Performance of magnetic nanocomposites for the removal of some selected contaminants from aqueous solution
- Authors: Ojemaye, Mike Onyewelehi
- Date: 2017
- Subjects: Nanocomposites (Materials)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8746 , vital:33508
- Description: In this thesis, the performances of magnetic nanoparticles based materials were assessed for the removal or reduction of heavy metals in aqueous solutions. The successful synthesis of a novel adsorbent, azomethine functionalized magnetic nanoparticles (MNP-Maph) by covalent bonding between the amine group (-NH2) of amine functionalized magnetic nanoparticles (MNP-NH2) and carboxylic group (-COOH) of 4-{[(E)-phenylmethylidene]amino}benzoic acid (Maph-COOH) was achieved. This adsorbent was examined for the removal of di and trivalent ions (Cu2+, Zn2+, As3+, Pb2+ and Hg2+) from aqueous solutions. Also, magnetic photocatalyst with silica interlayer (NiFe2O4-SiO2-TiO2) was synthesized and employed for the reduction of Cr(VI) in aqueous solution. The photocatalytic reduction efficiency of this material was compared with that of magnetic titanium dioxide (NiFe2O4-TiO2) photocatalyst and titanium dioxide (TiO2) to ascertain the material with the best photocatalytic efficiency and ease of separation. All synthesized materials were characterized by using XRD, FT-IR, TEM, SEM, TGA and VSM before application. For the adsorption processes, the effects of pH, contact time, adsorbent dose and temperature were examined to ascertain the experimental condition necessary for the optimal removal of metal ions from solution. The data obtained from all experiments were fitted into four kinetic models; pseudo-first order, pseudo-second order, elovich and intra particle diffusion models to determine the mechanism involved in the adsorption of these di and trivalent ions while two isotherm models were employed in the adorption processes; these include: Langmuir and Freudlich models. Also, for the photocatalytic experiment, the effects of pH, contact time and photocatalyst dose were investigated to determine the experimental conditions necessary for the optimal reduction of Cr(VI) in aqueous solution. MNP-Maph showed excellent removal capacities of 34.08, 35.83, 50.08, 58.24 and 59.24 mg g-1 for Cu2+, Zn2+, As3+, Pb2+ and Hg2+ respectively compared to data previously reported in literature. This is as a result of the high affinity of azomethine group towards metal ions which tremendously enhanced removal of metal ions by adsorption. The incorporation of azomethine to magnetic nanoparticles improved the affinity towards metal ions removal forming strong electrostatic interaction between the adsorbent active sites and adsorbates. Also, the utilization of NiFe2O4-SiO2-TiO4, NiFe2O4-TiO2 and TiO2 for the reduction of Cr(VI) in aqueous solution showed a good photocatalytic performance with NiFe2O4-SiO2-TiO2 showing to be better in terms of both photocatalytic reduction and magnetic separation. TiO2 was observed to have 96.7percent reduction efficiency within 240 min while NiFe2O4-SiO2-TiO2 has 96.5percent reduction efficiency within 300 min and NiFe2O4-TiO2 gave 60percent reduction efficiency within 300 min of UV irradiation. This magnetic photocatalyst composite (NiFe2O4-SiO2-TiO2) gives the advantage of avoiding the problem of separation often encountered with most photocatalyst materials including TiO2 by allowing separation with the aid of a magnetic field. The adsorption processes were all described by pseudo-second order and Langmuir isotherm models while the photocatalytic process was described by Langmuir-Hinshelwood (L-H) kinetic model. Furthermore, thermodynamic experiment studied for the adsorption processes showed that all metal ion adsorption except Hg2+ by MNP-Maph were endothermic in nature, rapid and spontaneous indicating the feasibility of the sorbent material for the removal of metal ions from aqueous solutions. Also, regenerability study conducted to determine the reusability of sorbent material after seven cycles showed the potential to reuse sorbent material seven times or more. The reusability of the sorbent material was observed to show a percentage of an average of 78percent using 50:50 mixture of 0.1 mol dm-3 HNO3 and HCl for all adsorption processes. For the photocatalytic experiment, regenerability using 0.1 mol dm-3 for 1 h was observed to be very impressive after 3 runs for all synthesized photocatalytic materials. This thereby implies that the removal of metal ions by these materials will not in any way introduce secondary pollutants into the environment. Rather, it will avert the production of secondary pollutants. Also, the use of simple conventional chemicals for the regeneration of synthesized materials showed that regeneration in this study is cost effective as regeneration has been known to cost about three quarter of the total operation and maintenance of an adsorption or photocatalytic process. Application of MNP-Maph to real wastewater sampled from five different wastewater treatment plants in Eastern Cape Province for the removal of Cu2+, Zn2+ and As3+ showed that removal efficiencies of approximately 80 percent were achieved for all three metal ions upon adsorption by MNP-Maph. These therefore show that the introduction of metal loving ligand such as Maph-COOH improved the efficiency of MNP towards the removal of heavy metal ions from aqueous solution. Also, silica positively influenced the performance of magnetic titanium dioxide towards Cr(VI) reduction and separation from aqueous solution. This study therefore showed that these materials should be considered for future applications in the area of water/wastewater decontamination.
- Full Text:
- Date Issued: 2017
- Authors: Ojemaye, Mike Onyewelehi
- Date: 2017
- Subjects: Nanocomposites (Materials)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8746 , vital:33508
- Description: In this thesis, the performances of magnetic nanoparticles based materials were assessed for the removal or reduction of heavy metals in aqueous solutions. The successful synthesis of a novel adsorbent, azomethine functionalized magnetic nanoparticles (MNP-Maph) by covalent bonding between the amine group (-NH2) of amine functionalized magnetic nanoparticles (MNP-NH2) and carboxylic group (-COOH) of 4-{[(E)-phenylmethylidene]amino}benzoic acid (Maph-COOH) was achieved. This adsorbent was examined for the removal of di and trivalent ions (Cu2+, Zn2+, As3+, Pb2+ and Hg2+) from aqueous solutions. Also, magnetic photocatalyst with silica interlayer (NiFe2O4-SiO2-TiO2) was synthesized and employed for the reduction of Cr(VI) in aqueous solution. The photocatalytic reduction efficiency of this material was compared with that of magnetic titanium dioxide (NiFe2O4-TiO2) photocatalyst and titanium dioxide (TiO2) to ascertain the material with the best photocatalytic efficiency and ease of separation. All synthesized materials were characterized by using XRD, FT-IR, TEM, SEM, TGA and VSM before application. For the adsorption processes, the effects of pH, contact time, adsorbent dose and temperature were examined to ascertain the experimental condition necessary for the optimal removal of metal ions from solution. The data obtained from all experiments were fitted into four kinetic models; pseudo-first order, pseudo-second order, elovich and intra particle diffusion models to determine the mechanism involved in the adsorption of these di and trivalent ions while two isotherm models were employed in the adorption processes; these include: Langmuir and Freudlich models. Also, for the photocatalytic experiment, the effects of pH, contact time and photocatalyst dose were investigated to determine the experimental conditions necessary for the optimal reduction of Cr(VI) in aqueous solution. MNP-Maph showed excellent removal capacities of 34.08, 35.83, 50.08, 58.24 and 59.24 mg g-1 for Cu2+, Zn2+, As3+, Pb2+ and Hg2+ respectively compared to data previously reported in literature. This is as a result of the high affinity of azomethine group towards metal ions which tremendously enhanced removal of metal ions by adsorption. The incorporation of azomethine to magnetic nanoparticles improved the affinity towards metal ions removal forming strong electrostatic interaction between the adsorbent active sites and adsorbates. Also, the utilization of NiFe2O4-SiO2-TiO4, NiFe2O4-TiO2 and TiO2 for the reduction of Cr(VI) in aqueous solution showed a good photocatalytic performance with NiFe2O4-SiO2-TiO2 showing to be better in terms of both photocatalytic reduction and magnetic separation. TiO2 was observed to have 96.7percent reduction efficiency within 240 min while NiFe2O4-SiO2-TiO2 has 96.5percent reduction efficiency within 300 min and NiFe2O4-TiO2 gave 60percent reduction efficiency within 300 min of UV irradiation. This magnetic photocatalyst composite (NiFe2O4-SiO2-TiO2) gives the advantage of avoiding the problem of separation often encountered with most photocatalyst materials including TiO2 by allowing separation with the aid of a magnetic field. The adsorption processes were all described by pseudo-second order and Langmuir isotherm models while the photocatalytic process was described by Langmuir-Hinshelwood (L-H) kinetic model. Furthermore, thermodynamic experiment studied for the adsorption processes showed that all metal ion adsorption except Hg2+ by MNP-Maph were endothermic in nature, rapid and spontaneous indicating the feasibility of the sorbent material for the removal of metal ions from aqueous solutions. Also, regenerability study conducted to determine the reusability of sorbent material after seven cycles showed the potential to reuse sorbent material seven times or more. The reusability of the sorbent material was observed to show a percentage of an average of 78percent using 50:50 mixture of 0.1 mol dm-3 HNO3 and HCl for all adsorption processes. For the photocatalytic experiment, regenerability using 0.1 mol dm-3 for 1 h was observed to be very impressive after 3 runs for all synthesized photocatalytic materials. This thereby implies that the removal of metal ions by these materials will not in any way introduce secondary pollutants into the environment. Rather, it will avert the production of secondary pollutants. Also, the use of simple conventional chemicals for the regeneration of synthesized materials showed that regeneration in this study is cost effective as regeneration has been known to cost about three quarter of the total operation and maintenance of an adsorption or photocatalytic process. Application of MNP-Maph to real wastewater sampled from five different wastewater treatment plants in Eastern Cape Province for the removal of Cu2+, Zn2+ and As3+ showed that removal efficiencies of approximately 80 percent were achieved for all three metal ions upon adsorption by MNP-Maph. These therefore show that the introduction of metal loving ligand such as Maph-COOH improved the efficiency of MNP towards the removal of heavy metal ions from aqueous solution. Also, silica positively influenced the performance of magnetic titanium dioxide towards Cr(VI) reduction and separation from aqueous solution. This study therefore showed that these materials should be considered for future applications in the area of water/wastewater decontamination.
- Full Text:
- Date Issued: 2017