In vitro investigation of the anti-hyperglycemic and chemical composition of Heteromorpha arborescens (Spreng.) Cham leaf extracts used in the management of diabetes mellitus
- Authors: Abifarin, Taiwo Oluwafunmilola https://orcid.org/00000003-4994-4638
- Date: 2021-09
- Subjects: Diabetes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22798 , vital:52760
- Description: Diabetes mellitus is currently a major threat all over the world. It is a chronic disorder characterized by elevated blood glucose levels and disturbance in carbohydrate, fat and protein metabolism which often times leads to several complications such as, atherosclerosis, diabetic nephropathy, retinopathy and neuropathy. Due to the side effects associated with synthetic oral hypoglycemic drugs, herbal remedies have become the alternative in the management of diabetes mellitus. Heteromorpha arborescens is one of the many plants used as herbal remedies for the management of diabetes mellitus in South Africa. In addition, the roots, barks and leaves are used in other parts of Southern Africa for the treatment of mental problems, asthma, cough, dysentery and tuberculosis. The roots are fed to malnourished children in Botswana and Swaziland. However, despite the high medicinal importance, there is little or no scientificinformation to prove this claim. Therefore, the basis of this study is to determine the chemical composition as well as perform and invitro investigation of the antihyperglycemic potential of H. arborescens leaf extracts to provide information that could validate the ethno-medicinal claims for the use of this plant in the management of diabetes mellitus. Phytochemical contents and antioxidant activity of the leaf extracts were determined. Phytochemical analysis of the acetone, ethanol, aqueous and blanched extracts of H. arborescens leaves indicated that the total phenol content of the extracts ranged between 15.10 mg GAE/g- 42.50 mg QAE/g, proanthocyanidin, 459-8402.1 mg QE/g and the flavonoid content, 109.24- 235.79 mg QE/g. In addition, alkaloids (7.65percent) and saponin (25.33percent) were present in significantamounts. Based on the IC50 values, the ethanol extract exhibited the highest total antioxidant activity (0.0125 mg/mL) with highest inhibition against DPPH and ABTS radicals (0.06 and 0.049 mg/mL respectively). Relatively high antioxidant activity may be attributed to the polyphenolic contents which possess hypoglycemic potentials. Minimum Inhibitory Concentrations (MIC) of H. arborescens leaf extracts against Bacillus pumilus, Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli and Klebselia pneumoniae was also determined and results indicated considerable antibacterial activity in the acetone, ethanol and blanched extracts with MIC values ranging from 1.563-12.5 mg/mL; however, the aqueous extract was inactive against all the bacteria strains. The antibacterial activity of the leaf extracts could be advantageous against diabetic related infections. The cytotoxicity, anti-obesity and antidiabetic potentials of blanched, aqueous and ethanol extracts of Heteromorpha arborescens (Spreng.) Cham leaves were also investigated. The results revealed that both ethanol and aqueous extracts indicated considerable inhibition against α-glucosidase (IC50 of 627.29 ± 4.33 μg/mL and 576.46 ± 3.21 μg/mL respectively) while the blanched extract showed weak α- glucosidase inhibition (IC50; 855.38 ± 4.29 μg/mL). The aqueous extract showed the best α- amylase inhibition (IC50; 583.74 ± 5.87 μg/mL) among the assessed extracts. However, weak α- amylase inhibition was observed in the ethanol (IC50; 724.60 ± 4.33 μg/mL) and blanched extracts (IC50; 791.63 ± 3.76 μg/mL) of H. arborescens leaves. Some level of glucose utilization in both C3A and L6 cells was also observed for the aqueous and ethanol extracts which may be attributed to the relatively lower toxicity levels present in them, however, glucose utilization was very weak for the blanched extract, which may be due to higher level of cytotoxicity it possessed. Relatively weak lipase inhibition was observed for the ethanol (IC50; 699.3 ± 1.33 μg/mL), aqueous (IC50; 811.52 ± 3.52 μg/mL) and blanched extract (IC50; 1152.7 ± 4.61 μg/mL) as compared to orlistat (IC50; 56.88 ± 0.11 μg/mL). However, there was no reasonable reduction in lipid accumulation observed in all the extract treated cells. The results obtained suggest that H.arborescens leaf extracts can serve as a potential tool for the development of new strategies for the treatment of diabetes and obesity. However, further analysis is required to ascertain its anti- obesity potential. Also, caution should be taken in the use of the plant at high concentrations in order to ensure safety and efficacy. Analyses were also carried out to determine the nutritional and antinutritional constituents of the plant for possible inclusion in the diet of diabetic patients. Proximate analysis revealed the presence of 8.5 percent total ash, 4.92 percent crude fat, 8.41 percent moisture, 15.74 percent crude protein, 21.48 percent crude fiber, 40.95 percent carbohydrates and 271.04 kcal/100g energy value. Mineral analysis showed that H. arborescens leaves are very rich in K, Ca, and Fe. Considerable amounts of Mg, Mn, Na, P, Cu and Zn were also present. Vitamin analysis showed that the plant has a high content of vitamins A, C and E. The anti-nutrients evaluated were phytate, oxalate, saponin, and alkaloids, all of which were below toxic levels except for saponin which was observed in moderately high level. This study revealed that H. arborescens leaves are a good source of nutrients and mineral elements, (with low anti-nutrient content) that are highly beneficial to human health especially in diabetic individuals, therefore, encouraging its possible inclusion as a vegetable. Essential oil composition of fresh Heteromorphaarborescens leaves were also determined by Solvent-Free-Microwave-Extraction (SFME) and Hydrodistillation (HD) methods and the compositions of both mehods were compared in terms of their chemical compositions, yield, CO2 emission and energy consumption. Solvent Free Microwave extraction method indicated higher oil yield of 0.7 mL/200 g (0.35 percent) as compared to 0.59 mL/200 g (0.295 percent), lower energy consumption and CO2 emission as compared to the hydrodistillation method. In conclusion, H. arborescens leaves indicated considerable potential efficacy in the management for diabetes mellitus and may require further structural elucidation and characterization in order to identify the bioactive constituents. , Thesis (PhD) -- Faculty of Science and Agriculture, 2021
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- Date Issued: 2021-09
International legal protection of women's reproductive rights: a comparative analysis of abortion laws and policies in four jurisdictions-Nigeria, Ghana, South Africa and U.S.A.
- Authors: Abiodun, Adeleke Funminiyi
- Date: 2010-10
- Subjects: Abortion -- Law and legislation , Reproductive right
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/25839 , vital:64491
- Description: The subject matter of abortion law is extremely broad and multi-disciplinary. While naturally having its basis in criminal and constitutional law of individual states, the global development of abortion discourse has been influenced by the need to protect the reproductive rights of women as a sub-set of international human rights laws; thereby advocating not only the decriminalisation of abortion but also, that individual State should take affirmative actions in promoting abortion as a right for every woman. However, that induced abortion is a punishable criminal act or a “protectable” woman’s reproductive right remains controversial due to the plethora of perspectives, beliefs and reservations held by different groups of people which are multi-dimensional and contradictory. This thesis therefore attempts a comparative study of abortion laws and policies in four jurisdictions: Nigeria and Ghana, operating criminalised abortion laws, South Africa and United States which operate liberalised/permissive abortion laws and policies. The study basically examines the legal status and reproductive rights of women to legal and safe abortion within the existing legal framework of national laws of the four selected jurisdictions vis-à-vis the legal protection offered by various international instruments on human rights. While we show that strict and restrictive abortion laws, and also, failure of States to create conditions for safe abortion constitute infractions of the reproductive rights of women, we submit further that over-liberalisation of abortion laws and policies could also amount to infringement of the basic rights of other people, thus there is need to ensure a legal and acceptable balance. The study finally acknowledges the role of international human rights laws in the protection of women’s right to legal and safe abortion but asserts that there can be no universally acceptable morality to which the whole world could subsume in term of women’s right to abortion due to the interplay of socio-cultural, religious, and moral affiliations of the people in different communities. , Thesis (LLD) -- Faculty of Law, 2010
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- Date Issued: 2010-10
Integration of nanostructured metal sulfides into titanium (iv) oxide for high performance dye sensitized solar cell
- Authors: Adedoyin Mojeed Agoro https://orcid.org/0000-0002-0434-9635
- Date: 2020-01
- Subjects: Nanostructured materials , Sulfur compounds
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/21523 , vital:48857
- Description: The work in this thesis describes synthesis, characterization and integration of nanostructured metal sulfides into titanium (IV) oxide for high performance dye sensitized solar cell. The synthesised single source precursors were evaluated using TGA, FTIR, , UV-Vis, PL,1H and 13CNMR, SEM, EDS, HRTEM, XRD, AFM, Raman, I-V, CV, Bode plot and EIS. TGA revealed the thermal degradation and quantified the mass percentage of metal sulphides as 33percent, 45percent and 27percent for CuS, PbS and SnS nanoparticles, respectively. FTIR analysis showed bands at 1580-1450 cm-1, and 1060-940 cm-1 tentatively assigned to C-N and C-S stretching frequencies correspondingly. The (M-S) stretching was observed at 577-406 cm-1 for the complexes using bis(N-di-isopropyl-N-octyldithiocarbamato) as primary ligands. IR spectra of bis(N-1,4-phenyl-N-(4-morpholinedithiocarbamato) as secondary ligands suggested the presence of (C-N) vibrations at 1508-1513 cm-1 for the complexes and 1507-1584 cm-1 for the ligands. The bands in the region of 973-1030 cm-1 were assigned to the complexes and 974- 983 cm-1 were attributed to the ligands, whereas vibration frequencies at 416-625 cm-1 were Nelson's Choice were included in these preliminary variety trials (PVTs) as checks. Twenty-five hybrids expressing high values for the Smith – Hazel selection index were identified across sites over years. Among those hybrids were two checks, namely Q16 (PAN5Q649R) and Q33 (Phb31MO7BR). The top five high – yielding hybrids selected based on the selection index were considered to be the most productive, stable and adaptable based on the GGE biplot and AMMI stability values. None of these single cross hybrids over yielded the best hybrid check (Q16) in the current study. A high potential environment, Centane, was the ideal environments for evaluating genotypes in the present study. The studies showed inbred lines L22, L23, L26, L28, L25, L29 and L31 to be low N stress tolerant at 0 kg N ha-1 based on the low N stress tolerance indices under glasshouse and the field conditions; they were also among the top ten grain-yielders under field conditions at 0 kg N ha-1. Also, in the NUE study, they were found to be among the top ten most N-efficient inbred lines under low N soils, under 30 kg N ha-1, and were among the top twenty-four inbred lines with high NUE values across the N levels in the study. Inbred lines L29 and L22 also produced testcross hybrids that were among the top twenty based on GY under 0 kg N ha-1. The testcross hybrids produced from these inbred lines were also among the top twenty-five with outstanding SCA effects for GY. These inbred lines were also parental lines of some of the top twenty- five best hybrids selected based on the Smith – Hazel selection index in the PVT study. Inbred lines L22, L23, L26, L28, L25, L29 and L31 can therefore further be evaluated and used as sources of N-tolerance genes in QPM breeding programs. tentatively assigned to M-S bond in the complexes. UV-Vis spectroscopy analysis for the complexes and from primary and secondary ligands are between within the range of 338 – 340 nm. PL studies of the primary ligands with metal complexes indicated emissions at 464 nm, 462 nm, 462 nm for Pb(II) and Sn(II), and Cu(II). The presence of secondary ligands was revealed by the absorption peaks at 455, 456 and 457 nm, exhibiting both the signals and chemical constituents of the respective ligands and their corresponding complexes. The electrochemistry in chapters 3 and 4 reveals that phase angle in the Bode plots changes with frequencies for Sn(II) complexes at 58, 57 and 8 respectively. Bode plots showed remarkable electronics of Cu(II) and Pb(II) complex interfaces. The CV curves exhibit two kinds of redox peaks indicating reduction at the negative potentials and oxidation at the positive potentials. The EIS, electrodes produced Rct for Pb(II), Cu(II) and Sn(II) electrodes in chapter 3. Moreover The EIS revealed that Sn(II) sensitizer displaced a stronger chemical capacitance and improved efficiency which could lead to better electron lifetime yield. The obtained CV exhibited anodic and cathodic peaks for Pb(II), connoting a reduction in Pb2+ and oxidation in Pb2-. Bode plot phase angle displayed Sn(II) and Pb(II) with maxima phase, indicating the presence of time constants of the electrode processes in Bis(N-1,4-Phenyl-N-Morhpo-dithiocarbamato bis(Mo/1,4-PHDTC) complexes. From the results in chapter 4, the XRD patterns exhibited good crystalline nature of CuS as a result of sharp and strong diffraction peaks obtained. There are eight peaks of 2θ angle between 26° and 79° relating to orthorhombic structure of SnS. While PbS has a cubic structure with polycrystalline nature, PbS/HDA and PbS both correspond to their crystalline planes of (200), (111), (220), (311), (222), (400), (331), (420) and (422) affirming to PbS QDs structure. SnS/HDA and SnS photosensitizers displayed eleven peaks between the values of 27.02° to 66.05° for SnS/HDA and 26.03° to 66.04° for SnS, in confirming the orthorhombic structure. SEM analysis revealed hexagonal structure for CuS, while PbS and SnS exhibited mesoporous nanostructures with spherical nanoparticles. HRTEM images indicated spherical nano-particles with particle sizes in the range of 3.14 - 44.39 nm. The outcome of HRTEM analysis revealed crystallite sizes varying as 10.90 – 11.57 nm, 3.14 – 5.95 nm and 14.96 – 44.39 nm for the CuS, PbS and SnS, originated from the primary ligands. HRTEM images originating from the Bis(N-1,4-Phenyl-N-Morhpo-dithiocarbamato bis(Mo/1,4-PHDTC) complexes indicated spherical nano-particles with particle sizes of 3.14 - 44.39 nm. Raman images in chapter 5 revealed the presence of Raman active modes of E2g 66 cm-1 and 304, cm-1 and E1g 627 cm-1 and 706 cm-1 for CuS, the active modes of TO 65 cm-1 and 2LO 626 cm-1 for PbS, active modes of B1g 69 cm-1 for SnS and 266 cm-1 for Ag. From the AFM results in chapter 5, CuS photosensitizer displayed a smooth surface and particle estimated to be 0.50 μm and height profile of 12percent. The PbS photosensitizer exhibited particle size of 1.82 μm and 0.654 μm for PbS/HDA, depicting a regular crystal growth rate. The size distribution of SnS nanoparticle at 357 nm connotes smooth surface and good compactness on the substrate. However, SnS/HDA at 122 nm displayed shape and size of non-symmetrical particles. AFM analysis in chapter 8 revealed good size roughness for CuS film. PbS exhibited particle size of 365 nm and size height of 18percent as the smoothest film, while PbS/HDA revealed 1.22 um size with 9percent size height. The evaluated particle sizes varied as 0.11- 1.18 um for SnS/HDA and 0.054 – 0.54 um for SnS films grown at 360 ℃ with size height of 16.8 and 8.4percent. The I-V efficiency obtained indicated that the CuS exhibited a much better efficiency in the QDSCs with higher Voc and the highest η being 2.85percent compared to CuS/HDA and Cu(II). High JSC of 11 mA/cm has been observed in the PbS/HDA QDSSCs, compared to the PbS and Pb(II) cells. The SnS/HDA exhibited a better performance compared to SnS and Sn(II) sensitizers due to the presence of HDA capping agent. , Thesis (MSc -- Faculty of Science and Agriculture, 2020
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- Date Issued: 2020-01
Cultivation, nutritional and pharmacological evaluation of Celosia argentea (L) Kuntze: an endangered wild vegetable in the Eastern Cape Province of South Africa
- Authors: Adegbaju, Oluwafunmilayo Dorcas
- Date: 2019-09
- Subjects: Celosia , Edible greens
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19806 , vital:43250
- Description: Green leafy vegetables are important in human nutrition, but their cultivation is limited to a few staple ones. These vegetables possess high nutritious and therapeutic properties that could help in achieving nutritional security and alleviating the burden of some diseases. A typical example is Celosia argentea, which in South Africa, is little known and grossly under-utilized despite its numerous nutritional and pharmacological values. The present study investigated the cultivation, nutritional and pharmacological potentials of C. argentea at three stages of maturity of two trials. Evaluation of cultivation in the greenhouse towards possible domestication of C. argentea included seed viability test, seed germination under varying temperatures (5, 10, 15, 20 25 30, 35, 40°C), light conditions (continuous light, continuous darkness, alternating light and dark (12h light/12 dark photoperiod) and sowing depths (0, 1, 2, 3, 4 and 5cm). The nutritional evaluation assessed the proximal, mineral, vitamins and antinutrient content of the plant; while pharmacological potentials of C. argentea were evaluated by investigating the ultramorphology, phytochemical content, anti-oxidant, antimicrobial, toxicity and cell-based anti-inflammatory properties of the plant at different stages of growth. Germination experiment revealed that optimum seed germination requirements for C. argentea were 25°C, alternating light and dark regime and a sowing depth of 1cm. Microrphological assessment of C. argentea revealed that the leaves were amphistomatic; with the abaxial surface having higher stomata density. Characteristic, distinguishing protuberances were observed at the polar ends of the stomata on the adaxial surface of the plant epidermis, and the major elements on the foliar epidermis were beryllium, carbon, oxygen and potassium; while pigmentation and colouration, showing localization of bioactive compounds were mostly at the site where trichomes were abundant. Growth parameters and yield potential (plant height, stem girth, leaf area, number of leaves, number of branches, number of days to flowering, number of flowers as well as dry and fresh weight) of C. argentea showed that for agricultural practices on the field, increase in growth parameters should be expected around 4-5 weeks after transplanting while higher yield should be expected around 7-9 weeks after transplanting. The results encouraged cultivation during summer or late spring for best farm management. Proximal, mineral, vitamins and anti-nutrients content of C. argentea at three different maturity stages of two trials were performed using AOAC, ALASA and inductively coupled plasma-optical emission spectrometer techniques. Results revealed that the pre-flowering stage of growth had the highest ash (28.15± 0.10 percent) and crude protein (25.80 ± 0.20 percent) contents. While post-flowering stage had the highest carbohydrate (28.51± 0.20 percent and 36.16± 0.22 percent), crude fibre (33.41± 0.87 percent) and energy (435.28± 27.6 percent) with low fat and moisture (8.43± 0.15 percent and 6.35±0.09 percent) contents respectively; while no marked demarcation in most mineral contents in all the growth stages was observed. Zinc was highest at the flowering stage of growth, while vitamin contents decreased as the plant approached maturation. Antinutrients content of the plant was not dependent on growth stage. Total phenols, flavonoids and proanthocyanidin content of C. argentea were evaluated colourimetrically, while the antioxidant potency of the aqueous, acetone and methanolic extracts was measured using 2,2 diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), Ferric reducing antioxidant power (FRAP) and total antioxidant capacity (TAC) models. All the solvent extracts of the flowering stage had the highest total phenolic (80.75±4.21GAE/g), flavonoids (946.19±7.87QE/mg) and proanthocyanidin contents (100.90±1.29 CE/g); with the acetone extracts showing significantly higher phytochemical content. The flowering stage exhibited the best radical inhibitory activity, with the methanol extract having the highest scavenging power for ABTS and DPPH radicals, while acetone extract showed the highest inhibition against FRAP and highest total antioxidant capacity. The antimicrobial potential of the aqueous acetone and methanolic extracts of C. argentea evaluated using agar dilution method against six bacteria (Klebsiella pneumonia, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Bacillus cereus) and four fungal strains (Candida glabarata, Candida albicans and Penicillium aurantiogriseum and Penicillium chrysogenum) showed that Streptococcus pyrogenes and P. aeruginosa were susceptible to the methanol extracts of all the growing phases of both trials at 10 mg/mL; while Klebsiella pneumoniae was susceptible at 10 mg/mL to only the methanol post-flowering extracts of both trials. C. albicans and P. aurantiogriseum were highly susceptible to all the extracts. Possible toxicity evaluated using brine shrimp lethality assay and calculation of LC50 against brine shrimp nauplii revealed that C. argentea was not toxic at any stage of maturity at all concentrations evaluated. Anti-inflammatory activities and cytotoxicity of C. argentea extracts evaluated using RAW 264.7 macrophages and 3T3-L1 cell lines revealed that the acetone extract of the flowering stage had moderate anti-inflammatory activity with no significant toxicity against activated macrophages. Findings from this study indicate that C. argentea is a safe functional leafy vegetable of high nutritional and pharmacological importance which can easily be cultivated and domesticated in South Africa. This could significantly alleviate the burden of micronutrient deficiencies among pre-school children in rural communities. , Thesis (PhD) (Botany) -- University of Fort Hare, 2019
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- Date Issued: 2019-09
Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24365 , vital:62645
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to- electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
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- Date Issued: 2011-01
Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24343 , vital:62638
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to-electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
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- Date Issued: 2011-01
Genetic diversity, resistance profile of HIV and risk assessment of mother-to-child transmission in pregnant women on anti-retroviral therapy in the Eastern Cape, South Africa
- Authors: Adeniyi, Oladele Vincent
- Date: 2018-12
- Subjects: Antiretroviral agents http://id.loc.gov/authorities/subjects/sh2003006231 , AIDS (Disease) in infants http://id.loc.gov/authorities/subjects/sh90004332
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19817 , vital:43254
- Description: Despite the initiation of life-long ART in HIV-infected pregnant women, the rate and determinants of infant HIV transmission are not known, especially in the poor resource settings of the Eastern Cape, South Africa. Maternal anti-retroviral therapy (ART) is crucial for elimination of mother-to-child transmission (MTCT) of HIV. However, the inevitable risks of emergence of HIV drug resistance poses significant threat to achieving this goal of HIV-free generation and keeping mothers alive. Also, it is unclear if women with high viral load at delivery have acquired clinically relevant mutations, which could confer resistance to the ART, thus, further increasing the risks of motherto- child transmission of HIV-drug resistance strains. In addition to the gaps identified in the prevention of mother-to-child transmission (PMTCT) context, the understanding of regional epidemics is crucial to the broader epidemiological profiling of HIV infections in the country. Despite the rapid influx of foreign nationals to South African and Eastern Cape Province, there has not been any molecular epidemiological studies profiling the HIV diversity in the Eastern Cape. , Thesis (PhD) (Microbiology) -- University of Fort Hare, 2018
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- Date Issued: 2018-12
Agro-morphological characterisation, nitrogen use efficiency and combining ability of quality protein maize (zea mays l.) genotypes for low nitrogen tolerance
- Authors: AdeOluwa, Olusola Oluyinka https://orcid.org/ 0000-0003-2145-7141
- Date: 2021-08
- Subjects: Corn -- Quality
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/21501 , vital:48855 , http://id.loc.gov/authorities/subjects/sh85032715
- Description: Low nitrogen stress tolerant Quality Protein Maize (QPM) genotypes will be of great benefit to farmers for increasing productivity in nitrogen depleted soils in the Eastern Cape (EC) Province, South Africa (SA). The current study evaluated: (i) QPM inbred lines for tolerance to low soil nitrogen, (ii) the Nitrogen Use Efficiency (NUE) of different QPM inbred lines, (iii) the combining ability of QPM genotypes for tolerance to low nitrogen, grain yield, and other agro-morphological traits, and (iv) the agro-morphological characteristics and adaptation of QPM hybrids to environments of different production potential in the Eastern Cape, South Africa. Thirty-two white-seeded QPM inbred lines obtained from CIMMYT-Zimbabwe and Quality Seeds (PTY) LTD were evaluated for tolerance to low soil nitrogen stress using two nitrogen (N) treatment levels: 0 kg N ha-1 and 30 kg N ha-1 under both glasshouse and field conditions at the Crop Research farm, University of Fort Hare, in two planting seasons. The study aimed at assessing the response of QPM inbred lines to low N, with a view to identifying low N tolerant types under both glasshouse and field conditions. Shoot length stress tolerance index (SHL STI) indicated lines L23, L29, L27, L13, L16, L17, L31, L14, L18 and L22 to be low soil N tolerant from the glasshouse study. From the field study, low N Stress Tolerance Index (STI) identified inbred lines L23, L31, L26, L28, L25, L29, L32, L4, L6, L3 and L2 as low soil N tolerant. These inbred lines also had high grain yields (GY) in the field under 0 kg N ha-1 (all ranked within the top ten except L2). They also had the potential for stable yields across environments considering their high Yield Stability Index (YSI), Mean Productivity (MP), Geometric Mean Productivity (GMP) and Stress Susceptibility Index (SSI) values. Both the glasshouse and field studies revealed inbred lines L22, L23, L26, L28, L25, L29 and L31 were common to both the glasshouse and field studies as being low soil N tolerant. These thirty-two parental QPM inbred lines were evaluated in the field for their nitrogen use efficiency (NUE) under five different nitrogen levels: 0, 30, 60, 90 and 120 kg N ha-1. The inbred lines studied under 0 kg N ha-1 and 30 kg N ha-1 indicated that N level expressed highly significant differences (P ≤ 0.001) for total nitrogen in biomass (Bio Total N), total nitrogen in grain (G Total N), grain yield (GY), nitrogen use efficiency (NUE) and almost all the indices estimated. The top six nutrient use efficient genotypes were L9, L14, L23, L25, L29 and L32 across N levels. However, the best and highest NUE was obtained from the lowest fertilizer dose, 30 kg N ha-1. Highly significant and positive correlation coefficients were found between Nitrogen Use Efficiency (NUE) and yield (+0.9), NUE and NUtE (+0.9), NUE and HI (Harvest Index) (+0.5), NUtE and yield (+0.99), HI and yield (+0.5) and NUtE and HI (+0.5). Thus, NUE, HI and NUtE could be good predictors of yield potential under low N soil conditions. Sixty-four testcross hybrids were generated from crossing these 32 QPM inbred lines with two QPM open pollinated varieties (OPVs) as testers in a line x tester design and were evaluated under 0 kg N ha-1 and 30 kg N ha-1 in the field. The objectives of the experiment were to: (i) identify high yielding hybrids with tolerance to low soil N in the EC; (ii) determine the combining abilities and mode of gene action for various traits under low and high nitrogen conditions; and (iii) group the inbred lines into heterotic groups for future use in the breeding program. Results revealed that under 30 kg N ha-1 (30N) condition, both additive and non-additive gene effects were observed with less importance of non-additive gene action for grain yield. Based on specific combining ability (SCA) effects, hybrids LNC22, LNC31, LOB22, LNC30, LNC29, LOB11, LNC18, LOB30, LOB19 and LNC24 showed outstanding performance under 0 kg N ha-1 (0N) condition with relatively acceptable SCA under 30N for yield. Inbred lines L6 (1.63), L22 (1.74), L29 (1.83) and L30 (1.24) showed positive and significant GCAs for grain yield under 0N. They were identified as the best combiners for grain yield as they were among the top ten performers for GCA under 0N. They can be very useful sources of low N tolerance genes. Two heterotic groups were formed under 0 kg N ha-1 and 30 kg N ha-1 conditions, and they will be useful for future hybrid development in the breeding program. Furthermore, these thirty-two QPM inbred lines were utilised as parental lines to generate seventy-six single cross hybrids. These single cross hybrids were evaluated across three environments of varying production potential in the Eastern Cape (EC), during the 2016/17 and 2017/18 summer seasons. Non-QPM hybrids namely PAN5Q649R and Phb31MO7BR, as well as QPM OPVs OBATANPA and Nelson's Choice were included in these preliminary variety trials (PVTs) as checks. Twenty-five hybrids expressing high values for the Smith – Hazel selection index were identified across sites over years. Among those hybrids were two checks, namely Q16 (PAN5Q649R) and Q33 (Phb31MO7BR). The top five high – yielding hybrids selected based on the selection index were considered to be the most productive, stable and adaptable based on the GGE biplot and AMMI stability values. None of these single cross hybrids over yielded the best hybrid check (Q16) in the current study. A high potential environment, Centane, was the ideal environments for evaluating genotypes in the present study. The studies showed inbred lines L22, L23, L26, L28, L25, L29 and L31 to be low N stress tolerant at 0 kg N ha-1 based on the low N stress tolerance indices under glasshouse and the field conditions; they were also among the top ten grain-yielders under field conditions at 0 kg N ha-1. Also, in the NUE study, they were found to be among the top ten most N-efficient inbred lines under low N soils, under 30 kg N ha-1, and were among the top twenty-four inbred lines with high NUE values across the N levels in the study. Inbred lines L29 and L22 also produced testcross hybrids that were among the top twenty based on GY under 0 kg N ha-1. The testcross hybrids produced from these inbred lines were also among the top twenty-five with outstanding SCA effects for GY. These inbred lines were also parental lines of some of the top twenty- five best hybrids selected based on the Smith – Hazel selection index in the PVT study. Inbred lines L22, L23, L26, L28, L25, L29 and L31 can therefore further be evaluated and used as sources of N-tolerance genes in QPM breeding programs. , Thesis (PhD) -- Faculty of Science and Agriculture, 2021
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- Date Issued: 2021-08
Surveillance study on pathogenic Acinetobacter species in freshwater environment of the Amathole and Chris Hani District Municipalities, Eastern Cape, South Africa
- Authors: Adewoyin, Mary Ayobami https://orcid.org/0000-0001-7489-7402
- Date: 2019-09
- Subjects: Acinetobacter infections http://id.loc.gov/authorities/subjects/sh95004928 , Acinetobacter http://id.loc.gov/authorities/subjects/sh91001451 , Nosocomial infections http://id.loc.gov/authorities/subjects/sh85092770
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19836 , vital:43257
- Description: This study evaluates the occurrence of medically relevant Acinetobacter species in three rivers, namely; Keiskamma, Tyhume and Great Fish in the Eastern Cape Province, South Africa in one year sampling regime (April 2017 - March 2018). The physicochemical parameters (pH, temperature (TEM), electrical conductivity (EC), total dissolved solids (TDS), salinity (SAL), total suspended solids (TSS), turbidity (TBS), dissolved oxygen (DO) and biological oxygen demand (BOD)) of the water bodies were measured. The presumptive Acinetobacter species recovered from the freshwater resources were recorded and further confirmed using molecular techniques. Similarly, confirmed isolates were subjected to speciation using species-specific primer sets for A. baumannii and A. nosocomialis. Also, virulence genes namely; afa/draBC, epsA, fimH, OmpA, PAI, sfa/focDE, and traT in the two Acinetobacter species were also determined using molecular method. In addition, the antibiogram characteristics of A. baumannii and A. nosocomialis isolated from the water samples were determined using standard methods. The antibiotic susceptibility test was performed using a panel of 12 antibiotics belonging to the aminoglycosides (amikacin, AK and gentamicin, GM), β-lactam/β-lactamase-inhibitor combinations (piperacillin-tazobactam, PTZ), cephems (ceftazidime, CAZ, cefotaxime, CTX, and cefepime, CPM), carbapenems (imipenem, IMI and meropenem, MEM), fluoroquinolones (ciprofloxacin, CIP), folate pathway inhibitors (Trimethoprim/sulfamethoxazole, TS), lipopeptides (Polymyxin B, PB) and tetracyclines (tetracycline, TET). Similarly, antibiotic resistance genes (ARGs) present in the Acinetobacter isolates were investigated including aminoglycoside resistance genes (aacC2, aphA1 and aphA2), β-lactamases resistance genes (blaTEM, blaSHV, blaOXA-1-like, blaCTX-M(GROUP 1), blaCTX-M(GROUP 2), blaCTX-M(GROUP 9), blaVEB, blaGES, blaPER, blaCTX-M-8/-25, blaOXA-48-like, blaVIM, blaIMP and blaKPC), fluoroquinolones resistance genes (qnrA, qnrB, qnrC, qnrD and qnrS), sulfonamide resistance genes (sul1 and sul2), and tetracycline resistance genes (tetA, tetB, tetC, tetM, tetL and tetO). The pH, EC, TDS, SAL, TEMP, TSS, TBS, DO, and BOD for Tyhume River ranged as follows: 7.2-7.7, 125-141 μS/cm, 62-71mg/L, 0.06- 0.07 PSU, 11.3-20.2oC, 30.0-89.6 mg/L, 35.0-96.0 NTU, 8.2-9.8 mg/L, 2.0-4.2 mg/L, while for Great Fish River, the parameters were 8.0-8.2, 274-369 μS/cm, 137-184mg/L, 0.13-0.18PSU, 12.7-22.3oC, 44.3-99.4 mg/L, 48.0-214.0 NTU, 7.8-9.9 mg/L, 3.1- 4.9 mg/L, and at Keiskamma River they were 7.5-7.9, 153.2-285.0 μS/cm, 86-143 mg/L, 0.07-0.14 PSU, 11.0-21.4oC, 27.0- 55.6 mg/L, 31-61 NTU, 8.3-9.8 mg/L, 3.0-6.0 mg/L. A total of 1107 presumptive Acinetobacter spp. were recovered from the rivers sampled of which 428, 370 and 309 isolates were recovered from Tyhume, Great Fish and Keiskamma rivers respectively. However, only 844 was confirmed positive for the genus Acinetobacter and are recovered in the proportions 285 (77 percent), 219 (70.9 percent) and 340 (79 percent) from Great Fish, Keiskemma and Tyhume rivers respectively. Our finding revealed that 410 (48.58 percent) and 23 (2.7 percent) of the isolates were confirmed to be A. baumannii and A. nosocomalis respectively. Also, 308 (75.12 percent percent) A. baumannii and 3 (13.04 percent) A. nosocomialis isolates exhibited one or more virulence genes out of the seven tested, whereas 102 (24.88 percent) and 20 (86.95 percent) of the A. baumannii and A. nosocomialis isolates did not harbour any virulence gene. Additionally, OmpA was the most prevalent (p<0.05) virulence gene found in A. baumannii with 69 (45.10 percent), 52 (50.98 percent) and 77 (49.68 percent) isolates from Great Fish, Keiskamma and Tyhume rivers respectively. The rates of susceptibilities of A. baumannii and A. nosocomialis to the antibiotics followed the order; Piperacillin-tazobactam (72.8 percent ; 73.9 percent), Ceftazidime (70.5 percent ; 91.3 percent), Cefotaxime (16.8 percent ; 17.4 percent), Cefepime (88.5 percent ; 95.7 percent), Imipenem (95.9 percent ; 100 percent ), Meropenem (92.7 percent ; 91.3 percent), Amikacin (97.6 percent ; 91.3 percent), Gentamicin (89.8 percent ; 87 percent), Polymyxin B (84.4 percent ; 91.3 percent), Tetracycline (74.7 percent ; 78.3 percent), Ciprofloxacin (75.9 percent ; 78.3 percent) and Trimethoprim/sulfamethoxazole (74.0 percent ; 73.9 percent) respectively. Both A. baumannii and A. nosocomialis were highly susceptible to all the antimicrobials tested except cefotaxime where 64 percent and 78 percent intermediate responses were observed in the species. At least 10 isolates of A. baumannii were resistant against each of the antibiotics used. The modal multiple antibiotics resistance phenotypes (MARPs) for Acinetobacter spp. was MARP 3 (29.87 percent) and the least was MARP 10 and 11 (2.6 percent each). The antimicrobial resistance index (ARI) was higher at two sampling sites KE2 (0.33) and TY1 (0.22). Similarly, MARI showed that sampling sites KE2 was a hotspot for multidrug-resistant Acinetobacter spp. Of the five classes of ARGs studied, there was a widespread of β-lactamases (blaTEM) in the two Acinetobacter species, followed by sul2, which were detected in 67 (63.2 percent) and 44 (49.4 percent) isolates respectively, across the rivers studied. We conclude that aquatic resources of the study community are important reservoirs of pathogenic Acinetobacter species and antibiotic resistance determinants. The occurrence of clinically-important Acinetobacter species suggests possible contamination of these selected rivers which are consumed by humans and livestock, as well as being used for irrigation system, and this constitutes a risk to public health. It also shows that A. baumannii and A. nosocomialis can thrive in the aquatic environment. This study suggests that direct utilization of water from these sources for domestic and other purposes without any form of pre-treatment should be avoided. It is, therefore, necessary for regulatory authorities to monitor the release of domestic and industrial wastewater into these water bodies in order to prevent outbreaks of epidemics. , Thesis (PhD) (Microbiology) -- University of Fort Hare, 2019
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- Date Issued: 2019-09
Effects of the use of manipulative materials on grade nine learners’ performance in fractions in public high schools in Chris Hani West Education District, South Africa
- Authors: Adom, George
- Date: 2020-01
- Subjects: Mathematics -- Study and teaching -- Activity programs.|0http://id.loc.gov/authorities/subjects/sh2010101041 , Acalculia in children.|0http://id.loc.gov/authorities/subjects/sh2002012422
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19371 , vital:43058
- Description: The purpose of this study was to investigate the effects of the use of manipulative concrete materials on grade 9 learners’ performance in fractions in public high schools in Chris Hani west education district, in the Eastern Cape Province of the Republic of South Africa. Two hundred and fifty (250) grade nine (9) learners, whose ages ranged between 13-16 years, and ten (10) educators teaching grade nine mathematics, were selected from 40 public high schools with the use of stratified, systematic random sampling, convenience and purposive sampling methods. One hundred and twenty-five (125) learners were put into the experimental group, and another one hundred and twenty-five (125) learners were put into a control group through systematic random sampling method. Pre-test, Post-test, and Control group quasi-experimental design were used as research designs to collect data. Two research instruments were developed. These included: A Fractions Achievement Test (FAT), and Students Questionnaire on Manipulative Concrete Materials (SQMCM). The experimental group were taught with the Manipulative Concrete Materials (Cuisenaire rods, Fraction bar/Fraction title, Paper folding and Computer assisted manipulative), whilst the control group was taught through the lecture method. Four (4) null hypotheses were generated and tested at 0.05 level of significance. The data collected were analysed using Analysis of Covariance (ANCOVA) to find the Mean, Standard Deviation and t-test. The mean and standard deviation were used to compare the pre-test and post-test results between the Experimental group and the Control group. The analysed results of the means, standard deviations and t-tests were used to reject the null hypotheses. The analysed results were illustrated as followed: Cuisenaire rods pre-test (mean = 8.372, SD=1.770), post-test (mean = 12,428, SD=4.732), t=13,024 p< 0.05. Hypothesis (H01) was rejected : Fraction tiles/fraction bars pre-test (mean = 8.372, SD=1.770), post-test (mean = 11,42, SD=3.67), t=12,10 p< 0.05. Hypothesis (H02) was rejected : Paper folding pre-test (mean = 8.372, SD=1.770), post-test (mean = 11,792, SD=4.256), t=12,024 p< 0.05. Hypothesis (H03) was rejected : Computer assisted manipulative pre-test (mean = 8.372, SD=1.770), post-test (mean = 12,212, SD=4.569), t=12,801 p< 0.05. Hypothesis (H04) was also rejected. The comparison of the mean scores and iv standard deviation between the Experimental groups and Control groups indicated that there was no significant difference in the Pre-test in all cases. On the other hand, the mean scores and standard deviations between the Experimental group and Control group in the Post-test showed a vast difference in all cases. There were improvement in the mean scores, and slightly difference in the standard deviations in the Experimental groups, whilst there were drops in the mean scores and standard deviations of the Control groups in all cases. From the studies, there was an indication that manipulative concrete materials have significant effects on grade nine learner’s performance in fractions. It was therefore suggested that manipulative concrete materials should be incorporated into the instructions of fractions in mathematics. , Thesis (PhD) -- Faculty of Education, 2020
- Full Text:
- Date Issued: 2020-01
The changing face of NEPAD and the challenges of facilitating sub-regional economic integration on the ECOWAS platform
- Authors: Agomuonso, Udo Robertson
- Date: 2013-03
- Subjects: New Partnership for Africa's Development , Economic Community of West African States , Sustainable development -- Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24783 , vital:63573
- Description: This research is intended to evaluate and study the challenges confronting NEPAD’s quest for sub regional economic integration in the ECOWAS domain. Political and economic integration has been part of African strategy to overcome fragmentation, marginalization and improve the continent’s position in the global political economy. Indeed, Africa needs integration more than any other continent or region in the world and this is why, it has had a fair share of regional integration arrangements all through her history. Unfortunately, these efforts have not paid off in the dimension of desired expectations. When NEPAD was established, it was given regional integration responsibilities, even though it was not a regional organization. It was mandated to drive regional integration in Africa by supporting the regional integration efforts of the regional economic institutions in Africa. After 10 years of existence, African leaders dissolved NEPAD and in its place, instituted the NEPAD Planning and Coordinating Agency (NPCA). This move was orchestrated by the seemingly slow progress made by NEPAD in this direction. NEPAD and ECOWAS has been working together to promote regional integration, but like in most parts of Africa, the challenges has been seemingly intractable. The study is anchored around the principles of integration as presented by the neo-functionalists theorists. Hence, the research attempted to provide an explanation of the performance and non-performance of NEPAD as a regional integration tool, within the confines of the theory. The findings show that while, there has been some level of success in this venture as evidenced by the projects that are on-going in the sub region, the fact remains that NEPAD did not deliver or actually delivered below expectations. However, this situation is reversible as the study submitted that, there is a future for regional integration in West Africa, Africa and the new NPCA, if the African Union pulls the right levers. , Thesis (PhD) -- Faculty of Social Sciences and Humanities, 2013
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- Date Issued: 2013-03
Investigation of the levels of PBDEs and PCNs in the surface water and sediments from selected waterbodies in the Eastern Cape Province, South Africa
- Authors: Agunbiade, Idowu Victoria https://orcid.org/0000-0001-5605-0312
- Date: 2021-06
- Subjects: Persistent pollutants , Water -- Purification -- Organic compounds removal , Organic water pollutants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22699 , vital:52660
- Description: Studies have revealed that persistent organic pollutants (POPs) are omnipresent in our environment; almost all human beings have definite levels of POPs in their bodies. Even fetus and embryos are not spared; they have been found to bear certain levels of POPs. So far, there are about 28 chemicals listed as POPs among which are polybrominated diphenyl ethers (PBDEs) and polychlorinated naphthalenes (PCNs). PCN and PBDE distributions have been reported from different sources around the world, but studies relating to PCNs occurrence and distribution in Africa, especially South Africa is still minimal. PBDEs have been reported to cause diabetes, cancer, damage to reproductive system, thyroid, liver and other vital organs in the body, while PCNs have been linked to chloracne (severe skin reactions/lesions) and liver disease (yellow atrophy) in humans, chicken oedema and X-disease in cattle. Hence, this study evaluates PCN levels in water and sediment samples from three waterbodies: North End Lake (NEL), Chatty River (CHA) and Makman Canal (MMC), while PBDE levels was reported in NEL and CHA samples. The three sites are located in Port Elizabeth, Eastern Cape Province (ECP) of South Africa. The lake serves as a recreational resort while the latter two waterbodies are tributaries discharging into the Swartkop Estuary, an important estuary in ECP. Water samples were extracted with C18 cartridges (solid phase), while soxhlet was employed for the extraction of sediments. Water and sediment extricates were purified and quantified with gas chromatography-micro electron capture detector (GC-μECD). Forty-seven (47) water samples and 44 sediment samples were collected in August until December 2020 from six sampling points in NEL, five points in each of CHA and MMC. All the samples were evaluated for physicochemical properties, PBDEs and PCNs using validated standard methods. The sampling period covered three South Africa seasons: August (winter), October (spring) and December (summer). The physicochemical parameters (PP) of NEL water samples for the three seasons generally varied as follows: temperature (15.3–23°C), pH (7.9–10.3), oxidation-reduction potential, ORP (23.4-110 mV), atmospheric pressure, AP (14.52-15.56 PSI), turbidity (15.1–167 NTU), electrical conductivity, EC (114–1291 μS/cm), total dissolved solids, TDS (55-645 mg/L), total suspended solids, TSS (20–107 mg/L) and salinity (0.05–0.65 PSU). All the PPs except for turbidity and TSS are within acceptable limits. NEL sediments had moisture content (MC), organic matter (OM) and organic carbon (OC) in the range of 0.04–8.0percent, 0.08–2.2percent and 0.05–1.8percent, respectively. The sum of eight PCN congeners Σ8PCNs and six PBDE congeners Σ6PBDEs in NEL water samples ranged from 0.164–2.934 μg/L and 0.009-1.025 μg/L individually. The values for Σ8PCNs and Σ6PBDEs in NEL sediment samples varied from 0.991–237 μg/kg and 0.354-28.850 μg/kg, respectively. The calculated hazard quotient (HQ) corresponding to the non-carcinogenic health risk associated with PBDEs in NEL water samples was 2.0×10-3-1.4×10-1, while the TEQ values due to PCNs varied from 6.10×10-7- 3.12×10-3 μg/L in NEL water samples and 3.70×10-5-1.96×10-2 μg/kg dw in sediments. The PP values for CHA water samples include temperature (15.4–22.9°C), pH (7.7–10.5), TDS (991–1771 mg/L), TSS (6–41 mg/L), turbidity (1.0–198 NTU), EC (1981–3542 μS/cm), AP (14.60–14.80 PSI), ORP (-339.1-51.3 mV), and salinity (1.02–1.87 PSU). The EC, TDS and salinity exceeded acceptable values at certain points. The sediments of CHA have MC, OM and OC contents ranging from 0.01-10.2percent, 0.2-1.3percent and 0.1-0.8percent in that order. Sum of Σ8PCNs, Σ6PBDEs in CHA water and sediment samples ranged from 0.026–1.054 μg/L, 0.007-0.079 μg/L and 0.429–1888.468 μg/kg, 0.347-6.468 μg/kg individually. The HQ in CHA water samples was 1.6×10-3-7.7×10-3 and the estimated TEQ was 1.0×10-7-6.62×10-5 μg/L and 1.10×10−5-6.40×10−2 μg/kg in water and sediments, respectively. The temperatures for MMC water samples ranged from 15.6-24.5°C, while other PPs recorded were as follows: pH (8.4-10.2), TDS (943–4002 mg/L), TSS (7-491 mg/L), turbidity (2.9-154.2 NTU), EC (1885-8004 μS/cm), AP (14.53–14.82 PSI), ORP (7.8-130 mV) and salinity (0.96-4.47 PSU). MMC’s sediments recorded MC, OM and OC varying as 0.4- 18.9percent, 0.2-4.5percent and 0.1-2.6percent, respectively across the three seasons. The Σ8PCNs for MMC water and sediment samples were 0.035–0.699 μg/L and 0.260–6744 μg/kg. The TEQ values in MMC water and sediment samples were 1.19×10-7-1.47×10-4 μg/L and 4.43×10−5- 4.19×10−1 μg/kg, respectively. The results are all less than one, and this suggests that the selected water is safe. Results showed that NEL water had highest TEQ, PCN and PBDE concentrations, while MMC sediments recorded maximum TEQ and PCN levels in this study. PBDE concentrations in NEL sediments were above the other site. In conclusion, NEL water was most polluted with both pollutants (PCNs and PBDEs), but MMC sediments contained more PCNs. There is need for the immediate remediation of these selected waterbodies. , Thesis (PhD) -- Faculty of Science and Agriculture, 2021
- Full Text:
- Date Issued: 2021-06
Study of the biotransformations and microbiological properties of cymbopogon citratus
- Authors: Ajayi, Emmanuel Olusegun https://orcid.org/0000-0002-0838-4948
- Date: 2015
- Subjects: Lemongras , Essences and essential oils
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19737 , vital:43197
- Description: Variations in the essential oil yield, chemical composition and kinetics of chemical transformation, antibacterial, and antioxidant properties of the Cymbopogon citratus cultivated in Alice, Eastern Cape of South Africa, over a period of 12 months using the solvent-free microwave extraction and the modified forms of conventional hydrodistillation methods have been evaluated. The modified forms involve variation in the pH medium to effect extraction and to obtain the whole leaf extracts of Cymbopogon citratus (lemongrass). The GC-MS analyses of the essential oils revealed the presence of 10, 11, 13, and 9 principal compounds in the microwave, extraction, hydrodistillation (water-distilled), hydrodistillation (aciddistilled and hydrodistillation (base-distilled), respectively with citral being the prominent compound in all the various extraction methods, with the water-distilled method having the highest cumulative citral content under the period specified. Each of the components of the oils varied in quantity and quality of yield at different points of the year. Different extraction methods produce different compounds. Increase in the amount of citral content was observed during the maturation stage of Cymbopogon citratus in all the extraction methods. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration (MIC) values were determined on the oils and extracts of Cymbopogon citratus using agar dilution method. The essential oils obtained using all the methods of extraction showed activity against all the tested bacteria at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the acid-distilled varied between 1.25 and 5.0 mg mL-1, while those obtained by both water- and base-distilled showed equal activity on the microorganisms with the MIC ranging between 2.5 and 10 mg mL-1. The microwave extraction showed the least activity with the MIC of 10 mg mL-1. This however suggested that the oils obtained through acid-distillation showed the greatest activity than all other methods of extraction. Activity of the various extracts on bacteria showed that the ethanol extract had the highest activity on the tested organisms with MIC ranging between 0.625 and 1.25 mg mL-1. This was closely followed by the acid-extract (1.25 and 5.0 mg mL-1), methanol extract (1.25 and 10 mg mL-1), acetone extract (2.5 and 5.0 mg mL-1), and base extract (5.0 mg mL-1). Both cold water and hot water extracts showed the least activity of MIC, >10 mg mL-1. The antioxidant and free-radical scavenging activity of the obtained oils and extracts were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay, [(2,2ˊ-azino bis-(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS), nitric oxide and ferric reducing power assays. The oils and extracts showed DPPH radical scavenging ability, but not as high as the standard drugs. The base extract showed a higher reducing power than the standard drug, rutin. There were significant differences in the phytochemicals contents of the various leaf extracts. The acetone extract has the highest flavonol, proanthocyanidin, and alkaloid contents. The ethanol extract showed the highest amount of phenolic content with the acid extract, having the least. Thin layer chromatography (TLC) and column chromatography was employed to obtain different fractions of extracts using four eluent solvent systems of varying polarities: toluene, petroleum ether, hexane and ethyl acetate and sprayed with anisaldehyde. A single, visible spot of B-fraction was developed, collected and analyzed as 1-methyl-2,4,5- trinitroimidazole with renown valuable properties. , Thesis (PhD) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015
Water restriction and vitamin c supplementation on Xhosa goats during summer: Effect on growth performance, blood biochemical profile, nutrient balance, carcass characteristics and meat quality
- Authors: Akinmoladun, Oluwakamisi Festus https://orcid.org/0000-0001-6462-374X
- Date: 2020-08
- Subjects: Goats -- Nutrition , Goats -- Feeding and feeds
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22710 , vital:52664
- Description: This study aimed to evaluate the effect of single and extra vitamin C (VC) supplementation on water-stressed Xhosa goats during the summer by evaluating their growth performance, blood biochemical profile, nutrient balance, carcass characteristics and meat qualities. The objectives were to assess the effect of water restriction and vitamin C supplementation by evaluating: firstly, growth performance, heat tolerance responses, and blood metabolites; secondly, intake, nutrient digestibility, nitrogen and mineral balance; thirdly, stress indices, carcass characteristics and meat qualities parameters and lastly, fatty acid profile, oxidative stability of lipids and sensory attributes were evaluated. To achieve these objectives, forty-two (42) goats were divided equally into seven treatments (75-day trial); without water restriction (W0, control); water restriction of 70percent of ad libitum water intake WI (W70); water restriction of 50percent ad libitum WI (W50); water restriction of 70percent of ad libitum WI plus 3g VC daily (W70+); water restriction 50percent of ad libitum WI plus 3g VC daily (W50+); water restriction of 70percent of ad libitumWI plus 3g VC and extra 5gVC given every eight-day (70++); water restriction of 50percent of ad libitum WI plus 3g VC and extra 5gVC given every eight-day (W50++). In the first objective, growth performance parameters, body condition scores, rectal temperature, respiratory rate, heat tolerance response parameters and blood metabolites were measured.Weight loss due to water restriction was reduced by VC supplementation in treated groups. The attenuation effect of VC was significant (P<0.05) in responses to respiratory rate (RR), Na+, K+, Mg2+, Cl-, Ca2+ and urea. Supplementation of VC (either single or multiple) did not (P>0.05) improve the effect of water restriction on body condition scores (BCs), FAMACHA©, glucose, globulin, alanine aminotransferase (ALT) and high-density lipoprotein (HDL). In the second objective, intake, nutrient digestibility, nitrogen and mineral balance were evaluated. The reduced nutrient intake was similar (P>0.05) irrespective of water restrictions and VC supplementations. Water-restriction levels did not affect nutrient intake/metabolic weight. Retained nitrogen increased with water-restriction levels but not influenced by VC. NH3-N decreased with the levels of water restriction while the pH was similar across the water restricted groups. Supplementation of VC had no effect (P>0.05) on apparent digestibility and digestible nutrients induced by water restriction levels. The amount of Ca, K, Mg retained increased (P<0.05) with water-restriction levels. In the third objective, stress indices, carcass characteristics and meat quality parameters were evaluated. The level of plasma cortisol concentration due to water stress was lessened (P<0.05) by VC. Follicle stimulating hormone (FSH), Luteinizing hormone (LH) and insulin were not affected (P>0.05) by levels of water restriction. The hot and carcass weights were lower (P<0.05) in W70+ and W50+ compared to W70 and W50 respectively. Vitamin C treated goats had higher redness (a*) compared to W70, W50 and W0. The shear force and cooking loss increased (P<0.05) with water restriction levels, while thaw loss, pH45min and pH24h were not affected by water restriction levels. In the final objective, the treatments did not affect (P>0.05) the oxidative stability of lipids (TBARS). The moisture and fat content in the water restricted groups were lower (P<0.05) than W0. The consumer meat sensory appearance decreased (P<0.05) with levels of water restrictions. Regardless of VC concentration and supplementation, vaccenic, and docosahexaenoic acid increased (P<0.05) while linolenic acid decreased as the water restriction levels increased. Nonetheless, treatment did not affect (P>0.05) the saturated and unsaturated fatty acids. These studies showed that suboptimal water intake negatively affects the growth performance and nutrient intake of Xhosa goats. However, the reduction in body weight loss and decreased plasma cortisol (chief stress hormone) concentration following vitamin C supplementation (especially at a daily single dose [3g/d]) may well reduce the effect of water stress in goats. , Thesis (PhD) -- Faculty of Science and Agriculture, 2020
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- Date Issued: 2020-08
Agricultural entrepreneurship development as strategy for economic empowerment: The case of small-scale farmers in Eastern Cape Province of South Africa
- Authors: Akinwale, Olusola Mokayode
- Date: 2020-11
- Subjects: Sustainable development -- South Africa -- Eastern Cape , South Africa -- Economic conditions
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/20241 , vital:45637
- Description: This study emanated from the struggle for economic empowerment among small-scale farmers in South African. The study advocates for the establishment of a viable environment where agricultural entrepreneurship can thrive. While the South African Nation Development Plan (NDP) proposed to create one million jobs through agricultural sector by 2030, the majority of small-scale farmers in South Africa are struggling to grow beyond the level of subsistence farming, and the youths appear not to be interested in the farming. It is therefore become necessary to conduct this current study that is exploratory in nature; it explored several factors and barriers to agricultural entrepreneurship development, as well as factors that can contribute to the development of prosperous and sustainable agricultural entrepreneurship among small-scale farmers in South African. The study was conducted in two district municipalities of Eastern Cape Province of South Africa – OR Tambo and Chris Hani. Both quantitative and qualitative research methods were used to make findings. Findings from the study shows that economic empowerment can be achieved through agricultural entrepreneurship development by giving adequate attention to specific factors like individuals’ attitude, production skills, access to market and marketing skills, management skills. Empirically, basic components like personal interests, adequate training and background, efficient extension service, famers’ network and communication, specific goal-oriented, understanding market, farmers’ collaboration, and access to sufficient funding are few of the factors that will make the small-scale farmers grow to the level of commercial farming. The study concluded that prerequisite to developing a sustainable agricultural entrepreneurship climate among small-scale farmers in South African is the combination of basic components aforementioned. Suggestions were made for strong collaboration between government and private sectors to provide development assistance for small-scale farmers as they struggles to develop their small-scale farming to sustainable entrepreneurship level. , Thesis (DPhil) -- Faculty of Management and Commerce, 2020
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- Date Issued: 2020-11
Effect of pomegranate (Punica granatum L) peel powder meal on growth performance, gut integrity, haemato-biochemical indices, meat, and bone quality of broiler chickens
- Authors: Akuru, Eunice Amaka https://orcid.org/0000-0002-3093-0247
- Date: 2022-04
- Subjects: Broilers (Chickens) , Meat -- Quality
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/23611 , vital:58218
- Description: The objective of the current study was to investigate the overall response of broiler birds to varying dietary levels of pomegranate (Punica granatum L) peel powder meal (PPPM). A total of 432-day-old Cobb 500 broiler chicks were randomly divided into six experimental groups of four replications with 18 birds per replicate in a completely randomized design (CRD). The birds were fed isonitrogenous and isocaloric experimental diets designated as: T1-control diet with 0percent additives (negative control; NEGCON); T2- control diet supplemented with α-tocopherol acetate at 200g per ton (positive control; POSCON): T3, T4, T5 and T6-control diet supplemented with 2, 4, 6 and 8g/kg PPPM (PPPM2, PPPM4, PPPM6, PPPM8). The phytochemical, nutritional and antioxidant properties of the pomegranate peel powder were determined. Results showed that the South African-grown pomegranate peel (“Wonderful” variety) had rich protein and trace mineral contents. Higher (p < 0.05) antioxidant and hepatic anti-lipid peroxidative activities were recorded in the ethanol and acetone extracts than the water extract, whereas the three extracts had no toxic effects on liver and kidney cells (p > 0.05). The dietary effects of PPPM supplementation on growth performance, digestibility, carcass, and organ weight indices of Cobb 500 birds were determined. The POSCON diet enhanced (p < 0.05) feed conversion ratio (FCR) at week 3. The average final body weight and average daily weight gain were highest (p < 0.05) in birds fed PPPM2 and PPPM4 diets, whereas birds fed PPPM2 diet had enhanced (p < 0.05) FCR and protein efficiency ratio when compared with birds on POSCON. Thigh and breast weights were highest (p < 0.05) in birds on PPPM4 and PPPM8 diets, whereas birds fed PPPM4 diet had enhanced (p < 0.05) nutrient digestibility compared with those on POSCON. The antioxidant status and breast meat quality of Cobb 500 broiler birds fed diets supplemented with PPPM were determined. Meat from birds fed PPPM8 diet had the highest (p < 0.05) thawing loss, while cooking loss was lowest (p < 0.05) in the PPPM2 group. The highest (p < 0.05) ability to scavenge ABTS [(2, 2-azinobis (3ethylbenzothiazoline-6 sulfonic acid))] radical cation (ABTS+) was recorded in the PPPM2 and PPPM4 meat while PPPM8 meat had increased (p < 0.05) catalase activity. The fatty acid composition, oxidative status, and drip loss in breast meat of Cobb 500 broiler birds fed graded levels of PPPM was determined. Meat from birds fed PPPM4 diet had the lowest (p < 0.05) margaric (C17:0) and arachidic (C20:0) acids, while meat from birds fed PPPM8 diet had higher (p < 0.05) levels of eicosadenoic (C20:2, n-6) and arachidonic (AA, 20:4) acids. The POSCON had higher (p < 0.05) ability to reduce TBARS levels in meat on day-1 and day-16 of storage than the NEGCON and PPPM diets, whereas TBARS levels were lowest (p < 0.05) in PPPM6 meat on day-16. The gut pH, histology, haematology, serum-biochemical indices, and bone quality parameters of Cobb 500 broiler birds fed diets supplemented with PPPM was determined. Birds fed POSCON, PPM2 and PPPM4 diets had the lowest (p < 0.05) pH in the duodenum, jejunum, and caecum, whereas duodenal pH values were lowest (p < 0.05) in birds fed PPPM2 and PPPM4 diets compared with birds on NEGCON. Birds fed PPPM4 diet had the highest (p < 0.01) duodenal, jejunal and ileal villi height (VH), and the highest (p < 0.01) VH to crypt depth (CD) ratio in the duodenum, jejunum, and ileum. The lowest (p < 0.05) CD in the duodenum, jejunum and ileum was also recorded in birds fed PPPM4 diet. Birds fed PPPM8 diet had higher (p < 0.05) values for white blood cell count, red blood cell count, haemoglobin concentration and packed cell volume, whereas the lowest (p < 0.05) concentration of serum aspartate transaminase was recorded in birds fed PPPM4 diet. Birds on PPM4 diet had longer (p < 0.05) bones. Bone weight and bone breaking strength were highest (p < 0.05) in birds fed PPPM8 diet. Tibia zinc and iron concentrations increased as the inclusion levels of pomegranate peel powder meal increased. It was concluded that broiler birds require 4 g/kg pomegranate peel powder for enhanced growth performance, nutrient digestibility, gut histology, quality, and antioxidant enzyme activity of meat, whereas 8 g/kg pomegranate peel powder meal supplementation is required for enhanced heamato-biochemical indices, bone quality, fatty acid composition and lipid peroxidative parameters in broiler birds. , Thesis (PhD) -- Faculty of Science and Agriculture, 2022
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- Date Issued: 2022-04
Pharmacological, toxicological and phytochemical evaluation of helichrysum petiolare hilliard & b.l. burtt - an indigenous plant traditionally used in the treatment of diabetes in the eastern cape province of South Africa
- Authors: Aladejana, Adebowale Emmanuel https://orcid.org/0000-0003-1871-926X
- Date: 2022-04
- Subjects: Diabetes -- Alternative treatment , Traditional medicine , Medicinal plants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22787 , vital:52755
- Description: Diabetes mellitus is one of the leading causes of death in South Africa, and it has already placed significant stress on the country’s health sector and economy. The orthodox hypoglycaemic drugs are not only ineffective in the management of the disease and its complications, but they also possess unwanted side effects. The need for alternative non-toxic drugs is therefore imperative. Various studies have listed several medicinal plants that can be successfully used in the herbal treatment of diabetes and have investigated them for their anti-diabetic potentials in vivo and/or in vitro. Out of the different potential herbal species, plants belonging to the Asteraceae family possess highly potent hypoglycaemic properties with negligible toxicities. Five Asteraceae plants widely used in different parts of South Africa for the treatment of diabetes were reviewed. The review provided an update of scientific evidence on the hypoglycaemic properties of the plants. However, Helichrysum petiolare was studied extensively in this study for its antidiabetic activity H. petiolare has been listed in many ethnobotanical surveys as a plant with potent hypoglycaemic potential, this, however, has not been properly verified in scientific literature and there has hardly been any study on the essential oil and nutritional composition, and antioxidant, antidiabetic, and cytotoxicity potentials of the plant. The effects of hydro-distillation (HD) and solvent-free microwave extraction (SFME) methods on the chemical constituents of H. petiolare-derived essential oils were evaluated. The SFME method had a higher yield of essential oil than the HD. There were substantial amounts of monoterpenes, monoterpene alcohols, sesquiterpenes, and sesquiterpene alcohols in both essential oils obtained, but these compounds were more profound in the SFME derived essential oil which has 62 compounds compared to the 52 derived through HD. The SFME derived essential oil can therefore be said to be of better quality than the HD method. The compounds obtained in the essential oils have high pharmaceutical and cosmetic value, and as observed in this study, their quantity is dependent on the method of extraction (Ibáñez and Blázquez, 2021; Kaur et al., 2021). The proximate analysis of the whole plant of H. petiolare showed high levels of Acid Detergent Fibre (ADF), vitamins (A, C and E), Neutral Detergent Fibre (NDF), and minerals. The high ADF level is believed to be responsible for the low energy, fat and carbohydrate levels observed in the study. The result showed a high level of oxalate and therefore suggests cooking of the plant before human consumption. Overall nutrition and mineral compositions of the plant showed that H. petiolare is immensely rich in vital nutrients that are of great importance to health and metabolism; these nutrients are suggested to be partly responsible for the plant’s useful medicinal properties. The phytochemical contents of the acetone (ACQ), ethanol (ETQ), and boiled (BAQ) and cold (CAQ) aqueous whole-plant extracts of Helichrysum petiolare were determined using standard phytochemical reaction methods. ABTS, DPPH, NO and TAC assays were used to evaluate their antioxidant properties. The highest total phenolic content (212,963 mg/g) was reported in the BAQ extract, while the ETQ had the highest flavonoid (172.393 mg/g) and proanthocyanidin contents (65.855 mg/g). Alkaloids, flavonols, and saponin were highest in the ACQ extract, while the CAQ had the lowest phytochemical content. Among the extracts, the BAQ had the highest DPPH•+ (IC50 0.02 mg/mL) and ABTS•+ (IC50 0.07) inhibition capacities, while the ETQ exhibited the highest NO• Inhibition (IC50 0.41 mg/mL) and TAC (IC50 0.19 mg/mL). These findings justify the use of H. petiolare in traditional medicine and further recommend the ETQ and BAQ extracts of the plant as more effective extracts for medicinal treatment. The hepatotoxicity (cytotoxicity, mitotoxicity and lipotoxicity) potential of the BAQ, CAQ and ETQ extracts of Helichrysum petiolare was evaluated using standard procedures. The results showed negligible BAQ and CAQ cytotoxicities, which were further, corroborated by stability in the mitochondrial membrane potentials and were congruent with the CAQ and BAQ results for steatosis and phospholipidosis. The data suggested favourable CAQ and BAQ toxicity profiles with limited risks for hepatotoxicity. The ETQ extract, however, showed significantly high levels of cytotoxicity and lipotoxicity, and a low level of mitotoxicity. Our result suggested a potential risk of the ETQ extract for hepatotoxicity but appears partly independent of direct mitochondrial involvement. Glucose uptake assay showed significantly increased glucose uptake in the BAQ and CAQ treated L6 and C3A cell lines. The CAQ extract enhanced glucose uptake more in the L6 myocytes than in the C3A cell-lines hepatocytes. The BAQ extract showed higher levels of inhibition on α–amylase and α-glucosidase activities as compared to CAQ. The BAQ and CAQ extracts of H. petiolare may, therefore, contain pharmacologically active and relatively non-toxic hypoglycaemic chemicals, which may be effective substitutes in the treatment of diabetes mellitus. This study provides up to date scientific information on the use of H. petiolare in the treatment of diabetes mellitus in the Eastern Cape of South Africa. It justifies the use of this plant in herbal medicine and sheds more light on its previously vaguely understood nutritional and medicinal potentials. More studies, however, need to be done to isolate, identify and purify the constituent bioactive compound(s). Their dosage of application and mode of action also needs to be understood. , Thesis (PhD) -- Faculty of Science and Agriculture, 2022
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- Date Issued: 2022-04
Preparation, characterization, and in vitro evaluation of polymer-based wound dressings for the management of chronic wounds
- Authors: Alven, Sibusiso
- Date: 2022
- Subjects: Toxicity testing -- In vitro , Wound healing , Chronic diseases
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/27992 , vital:71414
- Description: Microbial infections are responsible for the retarded recovery process of chronic wounds. Polymer-based scaffolds possess features suitable for the treatment of chronic injuries. However, these scaffolds are commonly encapsulated with therapeutic agents to enhance their biological activities, including antibacterial efficacy. In this research, two types of polymer-based scaffolds were formulated and evaluated as effective formulations for the treatment of chronic wounds: sponges and topical gels. Sponges were formulated from cross-linking of gelatin and PEG. Ag nanoparticles and metronidazole were incorporated into the sponges to improve their antibacterial activity. Topical gels were loaded with essential oils and Ag nanoparticles and prepared from CMC and poloxamer. The prepared sponges and topical gels were evaluated using various analysis and characterization techniques. SEM/EDX, FTIR, and TGA were employed to characterize gelatin/PEG hybrid sponges followed by porosity, in vitro biodegradability, cytotoxicity, and antibacterial studies. FTIR, SEM/EDX, and TGA confirmed their physicochemical properties and successful fabrication of sponges loaded with metronidazole and Ag nanoparticles. The sponges were biodegradable, indicating their capability to induce skin regeneration. The drug release studies showed a rapid release of metronidazole 28.32-71.97 percent from the sponges over the first hour, followed by a sustained drug release. The Ag nanoparticles were released in a sustained manner, suggesting that these sponges can rapidly destroy bacteria and inhibit persisting bacterial infections as well as protect the lesion bed from further bacteria infections. The in vitro antibacterial studies of sponges displayed superior antibacterial activity against most of the Gram-negative and Gram-positive bacteria strains commonly found in chronic wound infections with a MIC value of 15.625 μg/mL. In vitro cytotoxicity experiments revealed excellent biocompatibility with a percent cell viability of more than 70 percent. The in vitro wound scratch healing assay exhibited that the sponges encapsulated with only metronidazole promoted high cell migration than the dual drug-loaded sponges and untreated cells, suggesting its potential to quicken the wound healing process. CMC/Poloxamer topical gels were also characterized by FTIR, followed by pH, viscosity, spreadability, cytotoxicity, and antibacterial studies. FTIR showed successful preparation of CMC/Poloxamer topical gels loaded with essential oils and Ag nanoparticles. The topical gels exhibited pH in the range of 5.20-6.68, spreadability between 5.4 and 5.9 cm, and viscosity ranged from 216 to 1200 cP at 50 rpm and 210–858 cP at 100 rpm. The in vitro drug release studies demonstrated that Ag nanoparticles were released from the topical gels in a sustained manner. Most formulated topical gels demonstrated superior antimicrobial efficacy against Gram-positive and Gram-negative bacteria strains than the blank gel and controls. The cytotoxicity analysis displayed more than 90.83 percent cell viability for the topical gels, revealing excellent biocompatibility. The outcomes revealed that the topical gels enriched with essential oils lavender and tea tree and Ag nanoparticles and sponges incorporated with metronidazole and Ag nanoparticles are potential wound dressing scaffolds that can be employed for the treatment of chronic infected injuries. The in vitro wound healing experiments showed that the HaCaT cells cultured with gels co-enriched with lavender oil and Ag nanoparticles possessed a higher rate of closure in comparison to the untreated cells for 96 hours. , Thesis (PhD) -- Faculty of Science and Agriculture, 2022
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- Date Issued: 2022
Post-conflict reconstruction and development in South Sudan
- Authors: Annan, David https://orcid.org/0000-0001-9199-102X
- Date: 2019-08
- Subjects: Peace-building , Conflict management , South Sudan -- Politics and government -- 2011-
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19925 , vital:44486
- Description: The primary goal of this study was to identify possibilities for a common ground for reconciliation and restoring law and order through internally driven post-conflict reconstruction and development (PCRD) in South Sudan to prevent the recurrence of violent conflict and to attain peace, socio-economic and sustainable development. The existing literature about PCRD is mainly written by authors, policymakers and scholars who mostly support externally driven interventions and operations of ready-made ‘solutions’ to complex problems in war-torn countries without exploring internally driven approval to solve these conflicts. It is because of the failure of these externally driven approaches and the absence of a common goal for reconciliation that this study has been conceived to explore alternative approaches for reconciliation and post-conflict settlement to restore responsible law and order, build resilient good governance and to build legitimate state institutions in South Sudan. To better understand in-conflict and post-conflict societies and their needs, the study uses a qualitative methodology approach through explorative and interpretative mechanisms to purposely put together face-to-face interviews of people’s opinions on the current civil conflict in South Sudan. The findings indicate that for peace to be restored there is a need for an internally national dialogue and reconciliation and external actors must support locally driven initiation to enable lasting peace to prevail in South Sudan. The research uses cosmopolitan conflict transformation resolution (CCTR) to demonstrate perspective and knowledge of the South Sudanese on peace-building to provide an alternative contribution to efficient intervention in the South Sudan conflict. Without peace there cannot be effective lasting development and without development, it is almost impossible to establish lasting peace. Hence, the study views PCRD more as a sustainable development intervention through an internally driven approach than a market-biased political process to prevent relapse of violent conflict in South Sudan. , Thesis (PhD) -- Faculty of Management and Commerce, 2019
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- Date Issued: 2019-08
Comparative performance of 3-kWp ranges Solar Photovoltaic Systems under varying meteorological conditions in Alice, Eastern Cape Province, South Africa
- Authors: Apeh, Oliver Okechukwu https://orcid.org/0000-0003-4076-0613
- Date: 2021-08
- Subjects: Photovoltaic power systems , Solar energy
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/21567 , vital:48888
- Description: PVsystem has recently emerged in South Africa as a way to curb the country’s persistent shortage of electricity. A wide effort for the past few decades have targeted at study, testing and demonstration of PV power systems which was established all over the country as an appropriate measure to tackle transportation, agriculture, industry, commercial as well as domestic activities. In view of these drives, both off-grid and grid-connected PV systems are being applied. However, operating a building with an off-grid system is one of the means to providing the possibility of energy access to places far away from the national grid. As an off-grid choice, 50 W SHS is being distributed to customers in distant rustic parts of the country where grid option is difficult to access. But the SHS of the stated capacity can barely generate 0.3 to 0.4 kWh of electric energy per day, even at the optimal solar radiations. In view of this, more efforts are directed at expanding the off-grid systems to accommodate large rural households in South Africa. This thesis is dedicated to a study on the various configurations and components of PV power plant as a way to enhance electricity generations in South Africa. To this effect, different power plants were considered at SolarWatt park, University of Fort Hare with the aim to conduct a comparative analysis of the charge controllers with respect to the charge and discharge rates of their respective batteries. The grid-connected PV power generation was classified into hybrid PV and grid-assisted PV, while off-grid is a BIPV. These power plants generations were installed for the purpose of research level with a total capacity of 11.4 kW. The off-grid system is made up of HIT modules, FlexMax80 charge controller, Victron energy inverter and M-Molar battery bank. The hybrid and grid-assisted systems each consist of 15 polycrystalline modules and Microcare charge controllers. In addition, hybrid comprises SMA Sunny Island inverter and Trojan battery bank whereas grid-assisted consist of Microcare inverter and Hoppercke battery bank. The first part of the experimental work was monitored, and the meteorological parameters which are ambient temperature, solar radiation, relative humidity and wind speed, were measured and evaluated while electrical parameters includes PV current and voltage, MPPT current and voltage, battery current and voltage and inverter current and voltage were also measured and evaluated in the second part of the experiment. This lasted for a period of four years, starting from 1st January 2017 to 31st December 2020. Similarly, the second aspect was to monitor the electrical performance of the three systems and was performed for a period of six months, starting from January to June 2019. During the second experiment, hybrid and grid-assisted systems were reconfigured to function as off-grid systems. Moreover, a detailed data acquisition system designed to measure and record both meteorological and electrical parameters affecting the performance of the systems. The electrical parameters include PV current and voltage, MPPT current, battery current and voltage and inverter current and voltage. Other parameters in the measurements are; inverter efficiency, active and apparent power, while meteorological parameters include; solar irradiance, ambient temperature, relative humidity, wind speed and direction. The meteorological results show that the maximum and minimum mean amount of global solar radiation was 7.34 kWh/m2/day in December and 3.03 kWh/m2/day in June, respectively, while the average radiation and temperature for the typical year were 4.98 kWh/m2/day and 16.88 oC respectively. The solar radiations obtained are within the range in major places in South Africa. Similarly, an average wind speed of 2.5 m/s is experienced in Alice in a year and average solar radiation of 606.06 W/m2 in summer and 346.17 W/m2 in winter. The three lead-acid battery systems monitored under the electrical aspect are M-Molar, Trojan and Hoppecke battery systems. It was established that the charging current decreases gradually from 27.7 to 18.5 A for the M-Molar while Hoppecke and Trojan deceased respectively from 15 to 10 A and 23 to 13 A at the end of each phase by charging it at the maximum power point of the PV array. It was equally found that the M-Molar battery current has the highest rate of charging and quickest rate of discharging in comparison to the other two batteries. Finally, from the results gotten from this research, we may propose that the solar PV system contributes significantly to the satisfaction of the needed electricity in South Africa. , Thesis (PhD) -- Faculty of Science and Agriculture, 2021
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- Date Issued: 2021-08