The antifungal activity of an aqueous Tulbaghia violacea plant extract against Aspergillus flavus
- Authors: Belewa, Xoliswa Vuyokazi
- Date: 2015
- Subjects: Medicinal plants , Antifungal agents , Fungi -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/5858 , vital:21001
- Description: Phytochemical analysis of both HEA1 and the crude plant extract showed the presence of phenolics, tannins and saponins. Saponins were the predominant secondary metabolites and were mostly abundant in the plant extract and to a lesser extent in the active compound. Steroidal saponins, tannins and phenolics were also detected in the plant extract, but only the phenolics were detected in the active compound. The results of the phytochemical analysis showed that those compounds that were not present in the active compound could be removed from the crude extract during the TLC purification process. Investigation on the mechanism of action of the crude plant extract on the sterol production by A. flavus showed that the plant extract affected ergosterol biosynthesis by causing an accumulation of oxidosqualene in the ergosterol biosynthetic pathway resulting in a decline in ergosterol production. An oscillatory response in lanosterol production was observed in the presence of the plant extract, which may be an adaptation mechanism of A. flavus to unfavourable conditions and compensation for the loss of enzyme activity which may have occurred as a result of the accumulation of oxidosqualene. The antifungal activity of the plant extract on ergosterol production by A. flavus may also be due to saponins which target the cell membrane and ergosterol production in fungi. The effect of the plant extract on the fungal cell wall of A. flavus also showed that the plant extract caused a decline in β-(1, 3) glucan production by inhibiting β-glucan synthase. The plant extract also affected the chitin synthesis pathway of A. flavus, by causing a decline in chitin production, which was due to the inhibition of chitin synthase. Investigation of chitinase production using 4MU substrates showed that the plant extract caused an accumulation of chitobioses, by activating chitobiosidases and endochitinases. A decline in N-acetylglucosaminidase activity in the presence of the plant extract was observed and this prevented the formation of N-acetylglucosamine. The accumulation of chitobiosidase and endochitinase may be as a result of autolysis that may be triggered by A. flavus as a survival mechanism in the presence of the plant extract and as a compensatory mechanism for the loss of β-glucans and chitin. The antifungal effect of the plant extract on various components of the cell wall of A. flavus, makes T. violacea aqueous plant extract an ideal chemotherapeutic agent against both human and plant pathogens of Aspergillus. The broad spectrum of antifungal activity of T. violacea against A. flavus also eliminates any chances of the fungus developing resistance towards it and would make it a candidate for use as a potential antifungal agent. Further identification and possible chemical synthesis is needed to shed light on the safety and efficacy of the active compound for further development as a chemotherapeutic agent.
- Full Text:
- Date Issued: 2015
- Authors: Belewa, Xoliswa Vuyokazi
- Date: 2015
- Subjects: Medicinal plants , Antifungal agents , Fungi -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/5858 , vital:21001
- Description: Phytochemical analysis of both HEA1 and the crude plant extract showed the presence of phenolics, tannins and saponins. Saponins were the predominant secondary metabolites and were mostly abundant in the plant extract and to a lesser extent in the active compound. Steroidal saponins, tannins and phenolics were also detected in the plant extract, but only the phenolics were detected in the active compound. The results of the phytochemical analysis showed that those compounds that were not present in the active compound could be removed from the crude extract during the TLC purification process. Investigation on the mechanism of action of the crude plant extract on the sterol production by A. flavus showed that the plant extract affected ergosterol biosynthesis by causing an accumulation of oxidosqualene in the ergosterol biosynthetic pathway resulting in a decline in ergosterol production. An oscillatory response in lanosterol production was observed in the presence of the plant extract, which may be an adaptation mechanism of A. flavus to unfavourable conditions and compensation for the loss of enzyme activity which may have occurred as a result of the accumulation of oxidosqualene. The antifungal activity of the plant extract on ergosterol production by A. flavus may also be due to saponins which target the cell membrane and ergosterol production in fungi. The effect of the plant extract on the fungal cell wall of A. flavus also showed that the plant extract caused a decline in β-(1, 3) glucan production by inhibiting β-glucan synthase. The plant extract also affected the chitin synthesis pathway of A. flavus, by causing a decline in chitin production, which was due to the inhibition of chitin synthase. Investigation of chitinase production using 4MU substrates showed that the plant extract caused an accumulation of chitobioses, by activating chitobiosidases and endochitinases. A decline in N-acetylglucosaminidase activity in the presence of the plant extract was observed and this prevented the formation of N-acetylglucosamine. The accumulation of chitobiosidase and endochitinase may be as a result of autolysis that may be triggered by A. flavus as a survival mechanism in the presence of the plant extract and as a compensatory mechanism for the loss of β-glucans and chitin. The antifungal effect of the plant extract on various components of the cell wall of A. flavus, makes T. violacea aqueous plant extract an ideal chemotherapeutic agent against both human and plant pathogens of Aspergillus. The broad spectrum of antifungal activity of T. violacea against A. flavus also eliminates any chances of the fungus developing resistance towards it and would make it a candidate for use as a potential antifungal agent. Further identification and possible chemical synthesis is needed to shed light on the safety and efficacy of the active compound for further development as a chemotherapeutic agent.
- Full Text:
- Date Issued: 2015
Inhibitory potential of honey on the enzymatic activity of Helicobacter pylori urease
- Authors: Matongo, Fredrick
- Date: 2012
- Subjects: Honey , Helicobacter pylori infections , Enzyme inhibitors , Traditional medicine , Antifungal agents
- Language: English
- Type: Thesis , Masters , MSc (Biochemistry)
- Identifier: vital:11253 , http://hdl.handle.net/10353/431 , Honey , Helicobacter pylori infections , Enzyme inhibitors , Traditional medicine , Antifungal agents
- Description: Urease of Helicobacter pylori is an important virulence factor implicated in the pathogenesis of many clinical conditions, such as chronic gastritis, peptic ulceration, and gastric cancer. Many urease inhibitors have been discovered, like phosphorodiamidates, hydroxamic acid derivatives, and imidazoles. Despite good activities at the enzyme level and excellent kinetic properties most of them have not been used as therapeutic agents in vivo because of their side effects, toxicity and instability. This has led to much attention to focus on exploring the novel urease inhibitory activities of natural products because of their low toxicity and good bioavailability. Honey, a natural product has been used in folk medicine due to its antitumor, antioxidant, antimicrobial and anti-inflammatory properties. The aims of this study were to isolate, characterise, purify urease produced by H. pylori and investigate the inhibitory effects of solvent honey extracts on its enzymatic activity. Urease was found to be both surface-associated and cytoplasmic. Maximum cytoplasmic urease activity was found to occur after 72 hr whereas maximum extracellular urease activities were found to occur after 96 hr. Characterization of the crude cytoplasmic urease revealed optimal activity at a pH of 7.5 and temperature of 40°C. The kinetic parameters Vmax and Km were 45.32 U ml-1 and 61.11 mM respectively.The honey extracts inhibited the activity of the crude urease in a concentration dependent manner. The Lineweaver-Burk plots indicated a non-competitive type of inhibition against H. pylori urease. The two honey extracts gave promising inhibitory activities against urease of H. pylori. Thus the results of this study delineates that inhibition of urease can ease development in therapeutic and preventative approaches based on the enzymatic activity of this Helicobacter protein.
- Full Text:
- Date Issued: 2012
- Authors: Matongo, Fredrick
- Date: 2012
- Subjects: Honey , Helicobacter pylori infections , Enzyme inhibitors , Traditional medicine , Antifungal agents
- Language: English
- Type: Thesis , Masters , MSc (Biochemistry)
- Identifier: vital:11253 , http://hdl.handle.net/10353/431 , Honey , Helicobacter pylori infections , Enzyme inhibitors , Traditional medicine , Antifungal agents
- Description: Urease of Helicobacter pylori is an important virulence factor implicated in the pathogenesis of many clinical conditions, such as chronic gastritis, peptic ulceration, and gastric cancer. Many urease inhibitors have been discovered, like phosphorodiamidates, hydroxamic acid derivatives, and imidazoles. Despite good activities at the enzyme level and excellent kinetic properties most of them have not been used as therapeutic agents in vivo because of their side effects, toxicity and instability. This has led to much attention to focus on exploring the novel urease inhibitory activities of natural products because of their low toxicity and good bioavailability. Honey, a natural product has been used in folk medicine due to its antitumor, antioxidant, antimicrobial and anti-inflammatory properties. The aims of this study were to isolate, characterise, purify urease produced by H. pylori and investigate the inhibitory effects of solvent honey extracts on its enzymatic activity. Urease was found to be both surface-associated and cytoplasmic. Maximum cytoplasmic urease activity was found to occur after 72 hr whereas maximum extracellular urease activities were found to occur after 96 hr. Characterization of the crude cytoplasmic urease revealed optimal activity at a pH of 7.5 and temperature of 40°C. The kinetic parameters Vmax and Km were 45.32 U ml-1 and 61.11 mM respectively.The honey extracts inhibited the activity of the crude urease in a concentration dependent manner. The Lineweaver-Burk plots indicated a non-competitive type of inhibition against H. pylori urease. The two honey extracts gave promising inhibitory activities against urease of H. pylori. Thus the results of this study delineates that inhibition of urease can ease development in therapeutic and preventative approaches based on the enzymatic activity of this Helicobacter protein.
- Full Text:
- Date Issued: 2012
Factors that influence guest satisfaction with the hospitality establishments: evidence from hospitality industry in Eastern Cape, South Africa
- Mxunyelwa, Siyabonga, Mtshokotshe, Z
- Authors: Mxunyelwa, Siyabonga , Mtshokotshe, Z
- Date: 2021-00-00
- Subjects: Hotels , Antifungal agents
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/6758 , vital:48990 , https://www.ijicc.net/index.php/ijicc-editions/2021/226-vol-15-iss-10
- Description: The management of guests’ satisfaction is imperative for the sustainability of hospitality establishments. The guests’ satisfaction is a lifeblood of a thriving hospitality establishment such as the hotel, guest house, lodge and Bed and Breakfast to mention but a few. The purpose of this paper was to examine the influence of the five dimensional factors of service quality on guest expectations and experiences in hotels in Eastern Cape, South Africa. Furthermore, the paper sought to analyse the factors among the five dimensions that have a main role in driving overall guest expectations and experiences. A purposive sampling method was employed in the data collection process. Primary data was collected through interviews with hotel managers in the Eastern Cape, South Africa. The analysis of variance (ANOVA) among factor was undertaken in order to analyse the five factors. The findings elucidate that tangibles, responsiveness and assurance play a significant role in driving guest expectations and experiences in the South African hotel industry. The paper further underscores that reliability and empathy are an integral part in providing memorable experience for the guests in hotels. Furthermore, service quality is one of the key aspects to guest expectations and experiences. Conversely, the tangible variable is deemed to be the most important factor driving guest expectations and experiences in the context of the South African hotel industry. It is evident from the findings of the paper improve guest expectations and experiences hoteliers should emphasise the following attributes: ‘reliability’, ‘empathy’ and ‘assurance. The findings of this paper makes a meaningful contribution to a better understanding of the main factors that influence guest expectations and experiences. The results of this paper have implications from a managerial point of view in the highly competitive South African hotel industry.
- Full Text:
- Date Issued: 2021-00-00
- Authors: Mxunyelwa, Siyabonga , Mtshokotshe, Z
- Date: 2021-00-00
- Subjects: Hotels , Antifungal agents
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/6758 , vital:48990 , https://www.ijicc.net/index.php/ijicc-editions/2021/226-vol-15-iss-10
- Description: The management of guests’ satisfaction is imperative for the sustainability of hospitality establishments. The guests’ satisfaction is a lifeblood of a thriving hospitality establishment such as the hotel, guest house, lodge and Bed and Breakfast to mention but a few. The purpose of this paper was to examine the influence of the five dimensional factors of service quality on guest expectations and experiences in hotels in Eastern Cape, South Africa. Furthermore, the paper sought to analyse the factors among the five dimensions that have a main role in driving overall guest expectations and experiences. A purposive sampling method was employed in the data collection process. Primary data was collected through interviews with hotel managers in the Eastern Cape, South Africa. The analysis of variance (ANOVA) among factor was undertaken in order to analyse the five factors. The findings elucidate that tangibles, responsiveness and assurance play a significant role in driving guest expectations and experiences in the South African hotel industry. The paper further underscores that reliability and empathy are an integral part in providing memorable experience for the guests in hotels. Furthermore, service quality is one of the key aspects to guest expectations and experiences. Conversely, the tangible variable is deemed to be the most important factor driving guest expectations and experiences in the context of the South African hotel industry. It is evident from the findings of the paper improve guest expectations and experiences hoteliers should emphasise the following attributes: ‘reliability’, ‘empathy’ and ‘assurance. The findings of this paper makes a meaningful contribution to a better understanding of the main factors that influence guest expectations and experiences. The results of this paper have implications from a managerial point of view in the highly competitive South African hotel industry.
- Full Text:
- Date Issued: 2021-00-00
Investigations of the assessment of bioequivalence of topical clotrimazole products using a dermatopharmacokinetic approach
- Authors: Parfitt, Natalie Rae
- Date: 2011 , 2010-07-05
- Subjects: Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3840 , http://hdl.handle.net/10962/d1007659 , Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Description: The specialised nature of the stratum corneum makes it an efficient barrier to foreign substances, including drug molecules. Therefore, cutaneous drug absorption is a slow and complex process of which stratum corneum penetration is the rate limiting step. The rate and extent of stratum corneum penetration by a drug compound depends greatly on the presence of penetration enhancing/retarding excipients and therefore the clinical outcomes of a product rely greatly on the components and quality of the formulation. Hence, establishing bioequivalence between topical products is crucial to ensure that patients receiving multisource drug products are assured of the same efficacy and safety as the brand product. Since locally acting topical formulations do not target the systemic circulation, conventional methods of assessing bioequivalence using plasma levels are not appropriate. Consequently, the current regulatory guidelines require comparative clinical trials to be carried out to show bioequivalence between topical products. As these studies are very expensive and time consuming, the development of a more direct and relatively rapid and inexpensive method for determining bioequivalence between topical products is required. Clotrimazole is an anti-fungal agent where the target site of action is in the stratum corneum. In this work, tape stripping, which involves the sampling of stratum corneum, was investigated as a tool for the determination of bioequivalence between topical clotrimazole products. The tape stripping method involved the analysis of each tape strip individually and standardization of stratum corneum thickness between subjects was carried out using TEWL measurements. This approach provided detailed information regarding the amount of clotrimazole present in the stratum corneum as well as the extent of drug penetration. Prior to the tape stripping studies an HPLC method was developed for the quantitative analysis of clotrimazole from the tape strip samples. This method was shown to be accurate and reproducible across the required range. It was also shown to be selective for clotrimazole in the presence of possible interfering substances such as those present in the tape adhesive and also skin components. The bioequivalence studies were conducted using a single “uptake” time point. In order to determine an appropriate dose duration for these studies a novel approach was employed, involving a preliminary dose duration study. For the bioequivalence investigations, Canesten® Topical cream was used as both test and reference products to determine if the method was capable of showing bioequivalence. Subsequently, Canesten® Topical cream was also compared to a 1% gel formulation to determine if the method could detect formulation differences. The conventional BE limits of 0.8 – 1.25 were used for the assessment of BE, however, the clinical relevance of using these limits for dermal studies is debatable since they are derived from oral pharmacokinetic studies. Therefore, the data from the tape stripping investigations were also assessed using more realistic limits of 0.75 – 1.33 and even 0.7 – 1.44. In addition to the tape stripping studies a novel method of determining the amount of drug present in the stratum corneum, the “Residual Method”, was investigated. This method involved assaying the amount of clotrimazole found in the residual formulation after a specified dose duration had elapsed and subtracting that amount from the amount of clotrimazole initially applied. The results of tape stripping investigations showed that, if the study is sufficiently powered, tape stripping may be used to determine bioequivalence according to the conventional limits, as well as possibly detect formulation differences between different clotrimazole products. Bioequivalence assessment using the widened intervals showed that fewer subjects were required to achieve a sufficient statistical power. The variability associated with this method was acceptable and tape stripping may therefore have the potential to be used as a BE tool in a regulatory setting for clotrimazole or other antifungal topical formulations. The “Residual Method” also showed promising results as a bioequivalence tool, but further investigation and extensive validation of this method is required before it can be suggested as a regulatory method. The results of these studies have clearly indicated that tape stripping has the potential to be used as an alternative to comparative clinical trails for the assessment of bioequivalence between clotrimazole formulations and also to assess bioequivalence between other antifungal products.
- Full Text:
- Date Issued: 2011
- Authors: Parfitt, Natalie Rae
- Date: 2011 , 2010-07-05
- Subjects: Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3840 , http://hdl.handle.net/10962/d1007659 , Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Description: The specialised nature of the stratum corneum makes it an efficient barrier to foreign substances, including drug molecules. Therefore, cutaneous drug absorption is a slow and complex process of which stratum corneum penetration is the rate limiting step. The rate and extent of stratum corneum penetration by a drug compound depends greatly on the presence of penetration enhancing/retarding excipients and therefore the clinical outcomes of a product rely greatly on the components and quality of the formulation. Hence, establishing bioequivalence between topical products is crucial to ensure that patients receiving multisource drug products are assured of the same efficacy and safety as the brand product. Since locally acting topical formulations do not target the systemic circulation, conventional methods of assessing bioequivalence using plasma levels are not appropriate. Consequently, the current regulatory guidelines require comparative clinical trials to be carried out to show bioequivalence between topical products. As these studies are very expensive and time consuming, the development of a more direct and relatively rapid and inexpensive method for determining bioequivalence between topical products is required. Clotrimazole is an anti-fungal agent where the target site of action is in the stratum corneum. In this work, tape stripping, which involves the sampling of stratum corneum, was investigated as a tool for the determination of bioequivalence between topical clotrimazole products. The tape stripping method involved the analysis of each tape strip individually and standardization of stratum corneum thickness between subjects was carried out using TEWL measurements. This approach provided detailed information regarding the amount of clotrimazole present in the stratum corneum as well as the extent of drug penetration. Prior to the tape stripping studies an HPLC method was developed for the quantitative analysis of clotrimazole from the tape strip samples. This method was shown to be accurate and reproducible across the required range. It was also shown to be selective for clotrimazole in the presence of possible interfering substances such as those present in the tape adhesive and also skin components. The bioequivalence studies were conducted using a single “uptake” time point. In order to determine an appropriate dose duration for these studies a novel approach was employed, involving a preliminary dose duration study. For the bioequivalence investigations, Canesten® Topical cream was used as both test and reference products to determine if the method was capable of showing bioequivalence. Subsequently, Canesten® Topical cream was also compared to a 1% gel formulation to determine if the method could detect formulation differences. The conventional BE limits of 0.8 – 1.25 were used for the assessment of BE, however, the clinical relevance of using these limits for dermal studies is debatable since they are derived from oral pharmacokinetic studies. Therefore, the data from the tape stripping investigations were also assessed using more realistic limits of 0.75 – 1.33 and even 0.7 – 1.44. In addition to the tape stripping studies a novel method of determining the amount of drug present in the stratum corneum, the “Residual Method”, was investigated. This method involved assaying the amount of clotrimazole found in the residual formulation after a specified dose duration had elapsed and subtracting that amount from the amount of clotrimazole initially applied. The results of tape stripping investigations showed that, if the study is sufficiently powered, tape stripping may be used to determine bioequivalence according to the conventional limits, as well as possibly detect formulation differences between different clotrimazole products. Bioequivalence assessment using the widened intervals showed that fewer subjects were required to achieve a sufficient statistical power. The variability associated with this method was acceptable and tape stripping may therefore have the potential to be used as a BE tool in a regulatory setting for clotrimazole or other antifungal topical formulations. The “Residual Method” also showed promising results as a bioequivalence tool, but further investigation and extensive validation of this method is required before it can be suggested as a regulatory method. The results of these studies have clearly indicated that tape stripping has the potential to be used as an alternative to comparative clinical trails for the assessment of bioequivalence between clotrimazole formulations and also to assess bioequivalence between other antifungal products.
- Full Text:
- Date Issued: 2011
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