African traditional medicine-antiretroviral interactions : effects of Sutherlandia frutescens on the pharmacokinetics of Atazanavir
- Authors: Müller, Adrienne Carmel
- Date: 2011 , 2011-03-28
- Subjects: Antiretroviral agents , Medicinal plants , Traditional medicine , AIDS (Disease) -- Treatment , HIV infections -- Drug therapy , Drug interactions , Pharmacokinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3859 , http://hdl.handle.net/10962/d1013373
- Description: In response to the urgent call for investigations into antiretroviral (ARV)-African traditional medicine (ATM) interactions, this research was undertaken to ascertain whether chronic administration of the ATM, Sutherlandia frutescens (SF) may alter the bioavailability of the protease inhibitor (PI), atazanavir (ATV), which may impact on the safety or efficacy of the ARV. Prior to investigating a potential interaction between ATV and SF in vitro and in vivo, a high performance liquid chromatography method with ultraviolet detection (HPLC-UV) was developed and validated for the bioanalysis of ATV in human plasma and liver microsomes. An improved and efficient analytical method with minimal use of solvents and short run time was achieved in comparison to methods published in the literature. In addition, the method was selective, linear, accurate and precise for quantitative analysis of ATV in these studies. Molecular docking studies were conducted to compare the binding modes and affinities of ATV and two major SF constituents, Sutherlandioside B and Sutherlandin C, with the efflux transporter, P-glycoprotein (P-gp) and the CYP450 isoenzyme, CYP3A4 to determine the potential for these phytochemicals to competitively inhibit the binding of ATV to these two proteins, which are mediators of absorption and metabolism. These studies revealed that modulation of P-gp transport of ATV by Sutherlandioside B and Sutherlandin C was not likely to occur via competitive inhibition. The results further indicated that weak competitive inhibition of CYP3A4 may possibly occur in the presence of either of these two SF constituents. The Caco-2 cell line was used as an in vitro model of human intestinal absorption. Accumulation studies in these cells were conducted to ascertain whether extracts and constituents of SF have the ability to alter the absorption of ATV. The results showed that the aqueous extract of SF significantly reduced ATV accumulation, suggesting decreased ATV absorption, whilst a triterpenoid glycoside fraction isolated from SF exhibited an opposing effect. Analogous responses were elicited by the aqueous extract and a triterpenoid glycoside fraction in similar accumulation studies in P-gp overexpressing Madin–Darby Canine Kidney Strain II cells (MDCKII-MDR1), which signified that the effects of this extract and component on ATV transport in the Caco-2 cells were P-gp-mediated. The quantitative analysis of ATV in human liver microsomes after co-incubation with extracts and components of SF was conducted to determine the effects of SF on the metabolism of ATV. The aqueous and methanolic extracts of SF inhibited ATV metabolism, whilst the triterpenoid glycoside fraction had a converse effect. Analogous effects by the extracts were demonstrated in experiments conducted in CYP3A4-transfected microsomes, suggesting that the inhibition of ATV metabolism in the liver microsomes by these SF extracts was CYP3A4-mediated. A combination of Sutherlandiosides C and D also inhibited CYP3A4-mediated ATV metabolism, which was in contrast to the response elicited by the triterpenoid fraction in the liver microsomes, where other unidentified compounds, shown to be present therein, may have contributed to the activation of ATV metabolism. The in vitro studies revealed the potential for SF to alter the bioavailability of ATV, therefore a clinical study in which the effect of a multiple dose regimen of SF on the pharmacokinetics (PK) of a single dose of ATV was conducted in healthy male volunteers. The statistical analysis showed that the 90 % confidence intervals around the geometric mean ratios (ATV + SF/ATV alone) for both Cmax and AUC0-24 hours, fell well below the lower limit of the "no-effect" boundary of 0.8 – 1.25, implying that the bioavailability of ATV was significantly reduced in this cohort of subjects. It may thus be concluded that if the reduction in bioavailability observed in this clinical study is found to be clinically relevant, co-administration of SF commercial dosage forms and ATV in HIV/AIDS patients may potentially result in subtherapeutic ATV levels, which may in turn contribute to ATV resistance and/or treatment failure. This research has therefore highlighted the potential risk for toxicity or lack of efficacy of ARV regimens which may result when ATMs and PIs are used concurrently and that patients and health care practitioners alike should be aware of these perils.
- Full Text:
- Date Issued: 2011
Biopharmaceutics of phenylpropanolamine
- Authors: Dowse, Roslind
- Date: 1984
- Subjects: Biopharmaceutics Pharmacokinetics Phenylpropanolamine Pharmacology High performance liquid chromatography
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3818 , http://hdl.handle.net/10962/d1004915
- Description: Phenylpropanolamine (PPA), a sympathomimetic amine, has been widely used over the past 40 years as a decongestant and, in much larger dosages, as an appetite suppressant. Considerable interest has recently been shown in this drug due to its increasing popularity as an over-the-counter anorectic agent. Much controversy exists concerning the unfavourable side-effects of PPA resulting from the higher doses required for appetite suppression and the potential of this drug for abuse. A literature search revealed a paucity of information concerning the determination of PPA in biological fluids and, most noticeably, on the pharmacokinetics of this drug. An original method for determining PPA in serum and urine using high performance liquid chromatography (HPLC) which has increased sensitivity over other published HPLC methods is presented here. The simplicity of the extraction from biological fluids and subsequent determination by HPLC, enables concentrations of PPA to be monitored after a single dose of the drug. This method is therefore readily applicable to bioavailability and pharmacokinetic studies. The dissolution profiles of 4 sustained-release formulations of PPA were determined in a modified USP rotating paddle apparatus and the samples analysed using HPLC. A mathematical equation was applied to these data which are expressed in terms of dissolution parameters. Oral test dosage forms and solutions of PPA were investigated in bioavailability trials using the developed HPLC method to analyse the urine and serum samples. Linear one body compartment kinetics were assumed and the WagnerNelson method used to transform in vivo serum data to absorption plots which were then fitted to the well known Weibull equation. In order to more appropriately characterize the kinetic processes of absorption, distribution and elimination, a more complex model was utilized which involved numerical integration of a series of differential equations. The data were fitted to these models using nonlinear regression techniques. The pharmacokinetics of PPA are shown to exhibit some evidence of nonlinearity. The absorption of the drug appears to be di scontinuous and PPA seems to favour a two body compartment model.
- Full Text:
- Date Issued: 1984
Synthesis and reactions of sugar chlorosulphates
- Authors: Glass, Beverley Dawn
- Date: 1982
- Subjects: Chemical reactions Sugar -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3826 , http://hdl.handle.net/10962/d1006145
- Description: Summary: Partially chlorosulphated derivatives were synthesised for the purpose of examining the reactions of the chlorosulphonyloxy group in the presence of free hydroxyl groups. The behaviour of the chlorosulphonyloxy group was investigated under acidic conditions. Since sterically favoured chlorosulphonyloxy groups undergo facile replacement by chlorine to form chlorodeoxy sugars, some compounds possessing chlorosulphonyloxy groups which,due to polar and steric effects are not replaced by chloride,were investigated with a view to possible activation of the unfavourable centres towards nucleophilic substitution, thereby making available previously inaccessible chlorodeoxy sugars.
- Full Text:
- Date Issued: 1982
Establishing a formulation design space for a generic clobetasol 17- propionate cream using the principles of quality by design
- Authors: Fauzee, Ayeshah Fateemah Beebee
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:20983 , http://hdl.handle.net/10962/5868
- Description: The pharmaceutical industry is global, is highly regulated and is able to achieve reasonable product quality but at high cost with maximum effort. Numerous challenges face the pharmaceutical industry and include a shrinking research pipeline, less innovation, outsourcing, investments, increasing research and development costs, long approval times, growth of the generic industry, failure to understand or analyze manufacturing failure and wastage as high at fifty percent for some pharmaceutical products. An efficient and flexible pharmaceutical sector should be able to consistently produce high quality pharmaceutical products at a reduced cost with minimal waste. As a result, Food and Drug Administration (FDA) and other agencies such as the International Conference on Harmonization (ICH) have embraced a “Quality by Design” (QbD) paradigm and this has become the “desired state” so as to shift manufacturing from being empirical to a science, engineering, and risk based approach. QbD is a systematic approach for the development of high quality pharmaceutical dosage forms that begins with predefined objectives based on the premise that quality must be built into and not tested into a product. QbD together with the establishment of a design space for dosage forms is a fairly new concept and there is limited published data on QbD concepts that report the entire process of identifying Critical Quality Attributes (CQA), design of a formulation and manufacturing process to meet product CQA, understanding the impact of material attributes and process parameters on product CQA, identification and controlling sources of variability in materials and processes that affect the CQA of a product and finally establishing, evaluating and testing a design space using both in vitro and in vivo approaches to assure that a product of consistent quality can always be produced. The objective of these studies was to implement a QbD approach to establish a design space for the development and manufacture of a safe, effective, stable generic formulation containing 0.05% w/w clobetasol 17-propionate (CP) that had similar in vitro and in vivo characteristics to an innovator product, Dermovate® (Sekpharma® Pty Ltd, Sandton, Gauteng, RSA). Such a product would pose a minimal risk of failure when treating severe skin disorders such as seborrhoeic dermatitis, extreme photodermatitis and/or severe psoriasis in HIV/AIDS patients in Southern Africa.
- Full Text:
- Date Issued: 2014
Application of dermal microdialysis and tape stripping methods to determine the bioavailability and/or bioequivalence of topical ketoprofen formulations
- Authors: Tettey-Amlalo, Ralph Nii Okai
- Date: 2008
- Subjects: Drugs -- Therapeutic equivalency Transdermal medication High performance liquid chromatography Nonsteroidal anti-inflammatory agents -- Bioavailability Nonsteroidal anti-inflammatory agents -- Effectiveness Nonsteroidal anti-inflammatory agents -- Testing Nonsteroidal anti-inflammatory agents -- Side effects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3796 , http://hdl.handle.net/10962/d1003274
- Description: The widespread acceptance of topical formulations intended for local and/or regional activity has prompted renewed interest in developing a model to determine the bioavailability of drugs in order to establish bioequivalence as a means of evaluating formulation performance of multisource products and also for use during formulation development. Current in vivo techniques such as blister suction and skin biopsy amongst others used to determine the bioavailability and/or bioequivalence of topical formulations are either too invasive to generate appropriate concentration-time profiles or require large numbers of study subjects thereby making the study expensive and time-consuming. Moreover, there are currently no sampling techniques that can demonstrate dermal bioavailability and/or bioequivalence of topical formulations intended for local and/or regional activity. Dermal microdialysis is a relatively new application of microdialysis that permits continuous monitoring of endogenous and/or exogenous solutes in the interstitial fluid. The technique is involves the implantation of semi-permeable membranes which are perfused with an isotonic medium at extremely slow flow rates and collection of microlitre sample volumes containing diffused drugs. Tape stripping, a relatively older technique, has been extensively used in comparative bioavailability studies of various topical formulations. However, due to shortcomings arising from reproducibility and inter-subject variation amongst others, the published FDA guidance outlining the initial protocol was subsequently withdrawn. The incorporation of transepidermal water loss with tape stripping has garnered renewed interest and has been used for the determination of drug bioavailability from a number of topical formulations. Hence the primary objective of this research is to develop and evaluate microdialysis sampling and tape stripping techniques, including the incorporation of the determination of transepidermal water loss, to assess the dermal bioavailability of ketoprofen from topical gel formulations and to develop models for bioequivalence assessment. A rapid UPLC-MS/MS method with requisite sensitivity for the analysis of samples generated from dermal microdialysis was developed and validated which accommodated the microlitre sample volumes collected. An HPLC-UV method was developed and validated for the analysis of samples generated from the in vitro microdialysis and in vivo tape stripping studies. The work presented herein contributes to a growing body of scientific knowledge seeking to develop a model for the determination of bioequivalence of pharmaceutically equivalent topical formulations intended for local and/or regional activity in human subjects.
- Full Text:
- Date Issued: 2008
Aspects of prostacyclin in experimental hypertension
- Authors: Botha, Julia Hilary
- Date: 1983
- Subjects: Prostacyclin Prostaglandins Prostaglandin endoperoxides Thromboxanes Hypertension
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3825 , http://hdl.handle.net/10962/d1006109
- Description: A new prostaglandin - prostaglandin X (later renamed prostacyclin or prostaglandin I₂ (PGI₂)), was discovered by Moncada, Gryglewski, Bunting and Vane in 1976. This unstable substance was shown to be produced by vascular tissue and to be a vasodilator and the most potent endogenous inhibitor of platelet aggregation known. Because of its properties, it appeared that a lack of it may be related to the development and or maintenance of hypertension, a disorder featuring vasoconstriction and an increased tendency to arterial thrombosis. The present studies aimed to investigate this possibility using a rat model. A bioassay for prostacyclin was first perfected. This consisted of a modification of the method used by Moncada, Higgs and Vane (1977): PGI₂ released by rat aortic strips, during incubation in tris buffer, was measured by assessing the ability of the incubate to inhibit adenosine diphosphate induced aggregation of human platelets, as compared to the inhibitory effect of standard prostacyclin sodium salt. The specificity of the assay for the detection of PGI₂ was tested. The abil ity of hypertensive rat aorta to release prostacycl in was investigated in two studies. The first compared aortas of Wistar rats of the New Zealand genetically hypertensive strain (GH) with those of matched normotensive Wistar controls. In the second study, hypertension was induced by wrappi ng the ri ght kidney with surgical silk and removing the contralateral kidney. Ten weeks later, aortic generation of prostacyclin by these animals was compared with that of matched sham controls which had received identical surgical manipulation but for the application of silk to the right kidney. Contrary to expectation, in both forms of hypertension, aortas of the rats with elevated pressure produced consistently more prostacyclin than those of matched controls. In order to discover more about the relationship between elevated pressure and elevated PGI₂ production, the effect of pressure reduction with hypotensive agents on the ability of GH rat aortas to produce prostacyclin, was investigated. After pressure had been controlled within normal range for one week (achieved by oral administration of furosemide, dihydralazine and reserpine for one month), aortic PGI₂ was reduced in comparison with matched GH controls. However, the reduction was not consistent and statistical significance was not reached. Because it was subsequently reported by other workers, that some of the hypotensive agents which had been employed may effect prostaglandin levels per se, no conclusions could be drawn from this study as to any possible direct relationships between pressure and aortic prostacyclin generating capacity. A further means of reducing elevated pressure (which had no inherent effect on prostaglandin levels) was thus sought. A mechanical method was eventually selected, application of a silver clip to the aortas of GH rats, just below the diaphragm, producing an immediate reduction in pressure distal to the constriction. Eighteen hours with later, PGI₂ production by these distal aortas those of matched sham GH controls and was was compared found to be consistently reduced. These results indicate that the ability to produce PGI₂ may be influenced by prior local pressure changes and that the increased capacity of hypertensive rat aortas to generate prostacyclin may be related to the increased mechanical transmural stress consequent on elevated pressure. Since haemostatic balance must be influenced not only by vascular PGI₂ generation but also by platelet sensitivity to PGI₂, the response of GH platelets to the anti-aggregatory effect of prostacyc1in was also investigated. As it had been shown by Sinzinger, Si1berbauer, Horsch and Gall (1981) that intra-arterial infusion of PGI₂ in humans decreased platelet sensitivity to the substance, the possibility existed that platelet sensitivity in hypertension might be reduced. This hypothesis was, however, invalidated as the sensitivity of GH platelets to the anti-aggregatory effect of PGI₂ was almost identical to that of normotensive controls. The shortcomings of the methodology and the possible importance of these findings in the hypertensive animal are discussed. The idea that elevated PGI₂ in hypertension may play a protective role both with respect to platelet aggregation and in attenuating further pressure rises is considered. It is finally suggested that it will be possible to draw more accurate conclusions as to the meaning of the increased PGI₂ generation in hypertension (both in relation to vascular tone and platelet function) only when details of production of, and sensitivity to, thromboxane A₂ are known. Thromboxane A₂ (TXA₂) is a vasoconstrictor and promotor of aggregation (Hamberg, Svensson and Samuelson, 1975) and it may be that, despite elevated vascular PGI₂ generation, the TXA₂/PGI₂ balance is still tipped in favour of vasoconstriction and platelet aggregation in hypertension.
- Full Text:
- Date Issued: 1983
Formulation development, manufacture and evaluation of a lamivudine-zidovudine nano co-crystal thermo-responsive suspension
- Authors: Witika, Bwalya Angel
- Date: 2020
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/140546 , vital:37897 , http://dx.doi.org/10.21504/10962/140546
- Description: Expected release date-April 2021
- Full Text:
- Date Issued: 2020
Development and validation of a health literacy measure for limited literacy public sector patients in South Africa
- Authors: Marimwe, Chipiwa
- Date: 2018
- Subjects: Health literacy -- South Africa , Patient education -- South Africa , Communication in medicine -- South Africa , Health literacy -- Social aspects -- South Africa , Poor -- Medical care -- South Africa , Analysis of variance , Multidimensional Screener of Functional Health Literacy (MSFHL)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62661 , vital:28227
- Description: The growing complexity of healthcare demands greater patient involvement and skills to navigate this complex system. It has therefore become increasingly important to identify individuals with inadequate health literacy, by using efficient, short and reliable measures for doing so. Most research on the development and validation of health literacy tests has been conducted in high-income countries, with very little reported from low-and middle-income countries (LMICs). Existing health literacy measures have come under scrutiny for their lack of cultural sensitivity, bias towards certain population groups and failure to acknowledge health literacy as a multidimensional concept. These measures usually have limited application in LMICs due to the significantly different structuring of healthcare systems, they overlook the extreme discrepancies in educational levels, and rely too heavily on the ability to read health information. No health literacy data for South Africa are available, and only a few health literacy-based research papers have been published in this country. The aim of the study was to develop and validate a health literacy measure that is contextually and culturally appropriate to measure health literacy in limited literacy public sector patients in South Africa. An Item Bank of 30 questions was developed with the input of a diverse expert consultant panel, and included skills-based and self-reported questions which ensured cultural, contextual and educational level appropriateness. The Information and Support for Health Actions Questionnaire (ISHA-Q) is a health literacy measure developed to assess health literacy for LMICs which includes 14 core scales. These were useful in ensuring coverage of a range of health literacy constructs within the Item Bank. The 30 questions were then allocated to one of three health literacy domains: Procedural knowledge, Factual knowledge and Access to healthcare, health services and social support. Ethical approval for the study was obtained. The questions were translated into isiXhosa and underwent pilot testing. Following pilot testing, 120 isiXhosa first-language speakers, at least 18 years old, who attended public sector facilities and had a maximum 12 years of education were recruited from a primary healthcare clinic in Grahamstown. An interpreter was trained and he participated in all interviews. A questionnaire was used to collect data on the 30-question Item Bank. The Multidimensional Screener of Functional Health Literacy (MSFHL) was used as the primary comparator.The second phase of the study involved the refinement of the 30 questions in the Item Bank, which involved a multi-stage process. Data were analysed statistically using t-test, correlations, chi-square and ANOVA tests at a 5% level of significance, in order to identify problematic questions. Item Response Theory was used to ascertain difficulty and discriminatory ability of the questions. Each question was further subjected to in-depth interrogation by a panel of healthcare professionals to ensure that questions were supported by the conceptual framework and the definitions of health literacy adopted for this study. The number of questions was reduced from 30 to 12, and formed the new Health Literacy Test - Limited Literacy (HELT-LL). To validate the HELT-LL, 210 patients with the same inclusion criteria as previously noted, were recruited from four primary healthcare clinics in the Eastern Cape Province. Individual interviews were conducted with the assistance of the interpreter to collect sociodemographic data as well as data from the HELT-LL, the primary comparator (MSFHL), and a secondary comparator which was a South African modified version of the Newest Vital Sign (NVS-SA). The HELT-LL was re-administered to 40 patients in a follow-up interview two weeks later. The HELT-LL categorised only 17.6% of the patients as having adequate health literacy, just over a third with inadequate health literacy, and the majority with marginal health literacy. Questions in the cognitively demanding Procedural knowledge domain were the most poorly answered, with a mean score of 48.6±24.9%. Patients had great difficulty performing the basic numeric tasks in this domain. The overall mean score for the HELT-LL was 52.8±18.4%, compared with the more cognitively demanding NVS-SA with a mean of 28.6±21.1%, and clearly illustrated the impact of the strategy to include in the HELT-LL a variety of questions with differing cognitive load. The MSFHL, which is based on demographic characteristics and perceived difficulties with reading and writing, had an overall mean score of 44.4±26.2%. Demographic characteristics including age, education and English literacy, were found to be good predictors of limited health literacy, with significant correlations being found between these variables and the mean HELT-LL score. An acceptable value for Cronbach’s alpha, excellent test-retest reliability and excellent concurrent validity show that the HELT-LL is a valid and reliable measure of health literacy in our target population. As there is a paucity of health literacy research emanating from developing countries, this study presents a significant contribution to literature. It is the first study to report the development and validation of a health literacy measure to address the dearth of available health literacy measures applicable for South Africa. If implemented for use in clinical settings and for research purposes, it could provide valuable South African health literacy data which could inform the development of interventions focusing on improving health literacy and health outcomes.
- Full Text:
- Date Issued: 2018
The isolation, characterisation and chemotaxonomic significance of secondary metabolites from selected South African Laurencia spp. Rhodophyta
- Authors: Fakee, Jameel
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64696 , vital:28593
- Description: Bioprospection of marine organisms as a potential source for lead drugs is becoming increasingly popular. The secondary metabolome of these organisms consists of structurally diverse molecules possessing unprecedented carbon skeletons, the biosynthesis of which occurs via complex metabolomic pathways driven by specialist enzymes. This structural novelty is highly influential on the favourable bioactivity these compounds display. A prominent example of such a compound is trabectedin marketed as Yondelis®. Registered for the treatment of soft tissue sarcomas, this marine drug was developed from extracts of the tunicate Ecteinascidia turbinata. South Africa is renowned for possessing a highly diverse marine biota including several endemic species of marine red algae belonging to the Laurencia sensu stricto genus, which falls within the Laurencia complex. Despite having a good reputation for fascinating secondary metabolites, the taxonomy of Laurencia natural products is proving challenging for reasons including the presence of cryptic species, as well as individual species displaying morphological variability. The aim of this study was thus to isolate secondary metabolites from various South African Laurencia spp. and subsequently assess their chemotaxonomic significance by analysis of a parallel plastid rbcL phylogeny study of Laurencia spp. This study reports the first phycochemical investigation into Laurencia natalensis Kylin, Laurencia cf. corymbosa J.Agardh, Laurencia complanata (Suhr) Kützing, Laurencia sodwaniensis Francis, Bolton, Mattio and Anderson submitted, Laurencia multiclavata Francis, Bolton, Mattio and Anderson submitted, and a South African specimen of Laurenciella marilzae Gil-Rodríguez, Sentíes, Díaz-Larrea, Cassano and M.T. Fujii (basionym: Laurencia marilzae) originally described from Spain. Additionally, the chemical profiles of previously explored species Laurencia flexuosa Kützing and Laurencia glomerata Kützing were re-investigated. The organic extracts of the above species afforded 31 compounds belonging to a wide array of structural classes including halo-chamigranes, linear C15 acetogenins, indole alkaloids, cuparanes and cyclic bromo-ethers. A new tri-cyclic keto-cuparane (4.4) was isolated from L.cf. corymbosa alongside the new cuparanes 4.1 and 4.7. Algoane (5.9), a unique marker compound isolated from L. natalensis, was previously only reported from a sea-hare. Such marker compounds which are exclusive to an individual algal species increase the ease of their subsequent identification. The feasibility of chemotaxonomy as an additional tool to classify Laurencia spp. Was established as broad predictions of a specimen’s phylogeny, based on representatives of its secondary metabolome, proved viable. The study specimens were shown to possess similar chemical profiles to their sister species e.g. L. complanata, L. sodwaniensis and L. multiclavata produced similar metabolites to their sister species as inferred by an rbcL phylogeny tree. Finally, a 1H NMR profiling study on the crude organic extracts of various Laurencia spp. generated distinctive, reproducible spectra, exposing the value of NMR spectroscopy as a rudimentary species discernment tool.
- Full Text:
- Date Issued: 2015
Melatonin and anticancer therapy interactions with 5-Fluorouracil
- Authors: Cassim, Layla
- Date: 2008
- Subjects: Melatonin Melatonin -- Therapeutic use Antineoplastic agents Fluorouracil Fluorouracil -- Toxicology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3746 , http://hdl.handle.net/10962/d1003224
- Description: On the basis of clinical studies, some researchers have advocated that the neurohormone and antioxidant melatonin, shown to possess intrinsic anticancer properties, be used as co-therapy in cancer patients being treated with the antineoplastic agent 5-fluorouracil, as increased patient survival times and enhanced quality of life have been observed. The focus of this research was thus to investigate the mechanisms of this seemingly beneficial drug interaction between 5-fluorouracil and melatonin. Metabolism studies were undertaken, in which it was established that there is no hepatic metabolic drug interaction between these agents by cytochrome P450, and that neither agent alters the activity of this enzyme system. Co-therapy with melatonin is thus unlikely to alter plasma levels of 5-fluorouracil by this mechanism. Novel mechanisms by which 5-fluorouracil is toxic were elucidated, such as the induction of lipid peroxidation, due to the formation of reactive oxygen species; decreases in brain serotonin, dopamine and norepinephrine levels, possibly leading to depression; hippocampal shrinkage and morphological alterations and lysis of hippocampal cells, which may underlie cognitive impairment; and a reduction in the nociceptive threshold when administered acutely. All these deleterious effects are attenuated by the co-administration of melatonin, suggesting that the agent exhibits antidepressive and analgesic properties, in addition to its known antioxidative and free radical-scavenging abilities. This suggests that melatonin cotherapy can significantly decrease 5-fluorouracil-induced toxicity, but this may also exert a protective effect on cancer cells and thus compromise the anticancer efficacy of 5-fluorouracil. It was, furthermore, found that stimulation of indoleamine 2,3-dioxygenase activity, mediated by increases in superoxide anion and interferon-γ levels, may underlie resistance to 5-fluorouracil therapy. Melatonin was shown to increase superoxide anion levels in vivo, and this is believed to be by conversion to the metabolite and known oxidant 6- hydroxymelatonin. This highlights that the possible deleterious effects of melatonin metabolites should be studied further. Serum corticosterone levels and cytokine profiles are unaltered by both 5-FU and melatonin, suggesting that these agents may be used by HIV infected individuals without promoting the progression to AIDS. It can thus be concluded that melatonin co-therapy is potentially useful in countering 5-fluorouracil toxicity.
- Full Text:
- Date Issued: 2008
An investigation into the physico-chemical and neuroprotective properties of melatonin and 6-hydroxymelatonin
- Authors: Maharaj, Deepa Sukhdev
- Date: 2003
- Subjects: Melatonin Nervous system -- Degeneration -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3768 , http://hdl.handle.net/10962/d1003246
- Description: Until the beginning of this decade the antioxidant, melatonin, had been considered as little more than a tranquilizing hormone, responsible for regulating certain circadian and circannual rhythms. However, it is the discovery of melatonin as a free radical scavenger that has generated the most interest in recent years. The reduction of melatonin with age has been associated with neurodegenerative diseases such as Alzheimer’s disease (AD)and therefore, melatonin has been implicated to have an important clinical role in neuroprotection. Thus, for several years melatonin has attracted increasing attention from the general press with many advertisements touting this indoleamine to act as an aphrodisiac, rejuvenator, protector against diseases and a general wonder drug. However, melatonin formulations appear with no labelling for the correct storage conditions, dosage and side effects, as well as no control for purity and self-medicating with an unregulated product. In addition, there is much controversy surrounding the antioxidative properties of the indolemaine, 6-hydroxymelatonin (6-OHM). Therefore, the first part of this study aims to elucidate the physico-chemical and various stability characteristics of the pineal antioxidant, melatonin, while the second part is devoted to investigating the neuroprotective properties of the primary hepatic metabolite of melatonin, 6-OHM. The physical properties of melatonin were determined using various chemical techniques. This information served to both characterize and confirm the identity of melatonin raw material used in this study. In addition, this information serves to be essential as the physical properties of melatonin have not been reported in detail in literature, to date. Thereafter, using a validated high performance liquid chromatography (HPLC) method, the various physico-chemical and stability characteristics of melatonin were determined. Melatonin was shown to be extremely lipophilic, while the hygroscopic study indicates that melatonin raw material is extremely hygroscopic at temperatures above 40°C, whereas melatonin tablets are hygroscopic when left out of the original container. This study highlights the need for consumers to be aware of the proper storage of melatonin tablets to improve the stability and ensure long term integrity of the compound. Since, melatonin is most often administered orally, thus exposing it to a large variations in pH, within the gastrointestinal tract, it was decided to investigate the stability of melatonin over a range of pH’s and temperatures. The findings imply that melatonin is relatively stable at body temperature when ingested orally and that orally administered slow release preparations of melatonin should be relatively stable and therefore exhibit favourable bioavailability. However melatonin was shown to be unstable in solution. This provides important information and a challenge to the formulators of this drug substance in a liquid dosage form. An assessment of the photostability of melatonin dosage forms using International Committee on Harmonization (ICH) conditions revealed melatonin to be light sensitive and thus indicates a need for careful consideration of the packaging of these drug products. In addition a detailed assessment of the photochemistry and photoproducts formed during the UV photodegradation of melatonin is reported. Melatonin is shown to rapidly degrade in the presence of UV light, with the presence of oxygen accelerating the photodegradation. N1-acetyl-N2-formyl-5-methoxykynurenamine(AFMK) and 6-OHM were identified as the major photoproducts formed and these agents have been shown previously to retain antioxidant activity. One of the concerns of using melatonin in sunscreens is its photostability. However, it is reported in this study that the degraded solution of melatonin still possesses equipotent free radical scavenging ability as melatonin, despite the absence of melatonin in solution. In addition, melatonin is shown to reduce UV-induced oxidative stress in rat skin homogenate. Thus, these results make melatonin a likely candidate for inclusion in sunscreen preparations. Neuronal damage due to oxidative stress has been implicated in several neurodegenerative disorders. 6-OHM is not only formed as the major hepatic metabolite of melatonin, but also when melatonin reacts with toxic radicals as well as UV light. Thus the second part of the study aims to elucidate and further characterize the mechanism behind 6-OHM’s neuroprotection. The results show 6-OHM to be a more potent singlet oxygen and superoxide anion scavenger than melatonin. In addition, the results show 6-OHM to offer protection against, oxidative stress and lipid peroxidation induced by several neurotoxins in the rat brain and hippocampus. The hippocampus is an important region of the brain responsible for the formation of memory and any agent that induces stress in this area has detrimental effects and could lead to various types of dementia. Such agents include quinolinic acid (QA) and iron (II). Histological studies undertaken reveal that 6-OHM is able to protect hippocampal neurons against QA and iron (II) induced necrotic cell death. Immunohistochemical investigations showed that QA moderately induces apoptotic cell death in the hippocampus which is inhibited by both melatonin and 6-OHM. The study sought to elucidate possible mechanisms by which 6-OHM exerts its neuroprotective capabilities and the results show 6-OHM to inhibit the action of cyanide on the mitochondrial electron transport chain (ETC), one of the most common sources of free radicals. In addition, 6-OHM treatment alone, increased ETC activity above basal control levels and the results show 6-OHM to increase complex I activity in the mitochondrial ETC. Electrochemical, ultraviolet/visible spectroscopy (UV/Vis) and HPLC assessment show that an interaction exists between 6-OHM and iron (III) and 6-OHM is able to reduce iron (III) to a more biologically usable form viz. iron (II) which can be incorporated into important biomolecules such as heme. One dire consequence of this interaction is the ready provision of iron (II) to drive the Fenton reaction. However the biological and histological assessments show 6-OHM to prevent iron (II)-induced lipid peroxidation and necrotic cell death and thus, provide evidence of its antioxidant properties. The results also show 6-OHM to promote Hsp70 induction in the hippocampus. Heat shock proteins, especially Hsp 70 plays a role in cytoprotection by capturing denatured proteins and facilitating the refolding of these proteins once the stress has been relieved. 6-OHM treatment alone and together with QA was shown to increase the level of expression of Hsp70, both inducible and cognate forms of the protein. This suggests that 6-OHM helps to protect against cellular protein damage induced by any form of stress the cell may encounter. Melatonin treatment alone and in combination with QA was shown to prevent increases in the level of Hsp70 in the hippocampus, indicating that melatonin was able to reduce oxidative stress induced by QA such that Hsp70 expression was not required. The discovery of neuroprotective agents, such as melatonin and 6-OHM, is becoming important considering the rapid rise in the elderly population and the proportionate increase in neurological disorders. The findings of this study indicate the need for important information regarding the correct storage conditions and stability characteristics of melatonin dosage forms. In addition, the results indicate that 6-OHM has a definite role to play as an antioxidant. Thus further research may favour the use of these agents in the treatment of several neurodegenerative disorders.
- Full Text:
- Date Issued: 2003
An investigation into the feasibility of incorporating didanosine into innovative solid lipid nanocarriers
- Authors: Wa Kasongo, Kasongo
- Date: 2010
- Subjects: Antiretroviral agents HIV infections -- Drug testing Didanosine Nanoparticles Drug delivery systems Nanostructured materials Lipids -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3800 , http://hdl.handle.net/10962/d1003278
- Description: The research undertaken in these studies aimed to investigate the feasibility of developing and manufacturing innovative solid lipid carriers, such as solid lipid nanoparticles (SLN) and/or nanostructured lipid carriers (NLC) using a hot high pressure homogenization method, for didanosine(DDI). In addition, studies using in vitro differential protein adsorption were undertaken to establish whether the SLN and/or NLC have the potential to deliver DDI to the central nervous system (CNS). Prior to initiating pre-formulation, formulation development and optimization studies of DDI-Ioaded SLN and/or NLC, it was necessary to develop and validate an analytical method for the in vitro quantitation and analysis of DDI. An accurate, precise and sensitive RP-HPLC method with UV detection set at 248 nm was developed, optimized and validated for the quantitative in vitro analysis of DDI in formulations. Pre-formulation studies were designed to evaluate the thermal stability of DDI and to select and characterize lipid excipients that may be used for the manufacture of the nanocarriers. It was established that DDI is thermostable at temperatures not exceeding 163°C and therefore a hot high pressure homogenization technique could be used to manufacture DDI-loaded SLN and/or NLC. Lipid screening studies revealed that DDI is poorly soluble in both solid and liquid lipids. A combination of Precirol® ATO 5 and Transcutol® HP was found to have the best solubilizing-potential for DDI of all lipids investigated. The inclusion of Transcutol® HP into Precirol® ATO 5 changed the polymorphic form of the solid lipid from the stable 13-modification to a material that exhibited the co-existence between α- and β-polymorphic forms. The relatively high solubility of DDI in Transcutol® HP compared to Precirol® ATO 5 was an indication that a solid lipid matrix prepared from a binary mixture of Precirol® ATO 5 and Transcutol® HP was likely to have a higher loading capacity and encapsulation efficiency for DDI than a matrix consisting of Precirol® ATO 5 alone. Furthermore, the potential for the solid lipid matrix to exist in the α- and/or β-modifications when Transcutol® HP was added to Precirol® ATO 5 suggested that expulsion of DDI from a solid lipid matrix during prolonged storage periods was likely to be minimal. Therefore it was considered logical to investigate the feasibility of incorporating DDI into NLC and not in SLN. However, due to the limited solubility of DDI in lipids, formulation development of DDI-loaded NLC commenced using small quantities of DDI. Formulation development and optimization studies of DDI-loaded NLC were initially aimed at selecting a surfactant system that was capable of stabilizing NLC in an aqueous environment. Solutol® HS alone or a ternary mixture consisting of Solutol® HS, Tween® 80 and Lutrol® F68 was found to stabilize the nanoparticles in terms of particle size and the polydispersity index. The use of the ternary mixture as the surfactant system was preferred to using Solutol® HS alone as Lutrol® F68 and especially Tween® 80 have been successfully used to target the delivery of API to the brain. Aqueous DDI-free and DDI-Ioaded NLC containing increasing amounts of DDI were manufactured using hot high pressure homogenization at 800 bar for three cycles. The NLC formulations were characterized in terms of particle size, polydispersity index, zeta potential, and polymorphism, degree of crystallinity, encapsulation efficiency (EE), shape and surface morphology. The mean particle size for all formulations was below 250 nm with narrow polydispersity indices, indicating that narrow particle size distribution had been achieved. The d99% values for all formulations tested, were generated using laser diffractometry, and were below 400 nm, with span values ranging from 0.84 - 1.19 also suggesting that a narrow particle size distribution had been achieved. The zeta potential values measured in double distilled water with the conductivity adjusted to 50 μS/cm ranged from -18.4 to -11.4 mV. In addition, all the formulations showed a decrease in the degree of crystallinity as compared to the bulk lipid material and WAXS shows that the formulations existed in a single β-modification form. Furthermore DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. These parameters remained unaffected for most formulations following storage for two months at 25°C. In addition these formulations contained a mixture of spherical and non-spherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations. These studies showed that it was feasible to develop and incorporate small amounts of DDI into NLC. However in order to use these delivery systems for oral administration of DDI to paediatric patients, strategies to improve the amount of DDI that could be loaded into the particles and to achieve high encapsulation efficiencies had to be developed. The limited solubility of DDI in lipid media was identified as a major factor that affected the loading capacity and encapsulation efficiency of DDI in the NLC. Therefore, a novel strategy aimed at increasing the saturation solubility of DDI in the lipid by attempting to increase the dissolution velocity of the drug in the lipid using a particle size reduction approach, was designed and investigated. DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid medium was reduced gradually using hot high pressure homogenization and the product obtained from these studies was used to manufacture DDI-loaded NLC using a cold high pressure homogenization procedure. Although the encapsulation efficiency and drug loading following use of this approach was relatively high, the particles were large and showed a tendency to grow in size leading to the formation of microparticles after storage for two months at 25°C. In addition, the degree of crystallinity of the nanoparticles increased rapidly over the same storage period which led to expulsion of DDI nanoparticles for the NLC, despite the DDI loading in NLC being unaffected. It was clearly evident that this new approach of manufacturing solid lipid nanocarriers could be used as a platform not only for enhancing the loading capacity of DDI in solid lipid nanocarriers but also for other hydrophilic drugs. Differential protein adsorption patterns of DDI-loaded NLC were generated in vitro using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) in order to establish the potential for these systems to deliver DDI to the CNS. NLC formulations containing small amounts of DDI were used as these formulations showed a better stability profile than the formulation with a higher encapsulation efficiency and drug loading capacity. Furthermore, the encapsulation efficiency and drug loading of DDI were considered sufficient for use in 2-D PAGE studies. Data obtained from 2-D PAGE analysis reveal that DDI-loaded NLC preferentially adsorb proteins in vitro that are responsible for specific brain targeting in vivo. More importantly, these studies reveal that in addition to Tween® 80 that has already been shown to have the potential to target CDDS to the brain, Solutol® HS 15 has the potential to achieve a similar objective. Consequently, DDI-loaded NLC have the potential to deliver DDI to the brain and these results may be used as a platform for conducting in vivo studies to establish whether DDI can cross the blood brain barrier and enter the CNS when administered in NLC which may in turn lead to a major breakthrough in the management of HIV/AIDS and Aids Dementia Complex (ADC).
- Full Text:
- Date Issued: 2010
Biologically active natural products from South African marine invertebrates
- Authors: Hooper, Gregory John
- Date: 1997
- Subjects: Natural products -- South Africa Marine metabolites -- South Africa Marine invertebrates -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3761 , http://hdl.handle.net/10962/d1003239
- Description: This thesis describes the chemical and biological investigation of the extracts of six different marine invertebrate organisms collected along the South African coastline. The work on these extracts has resulted in the isolation and structural elucidation of twenty-one previously undescribed secondary metabolites; The history of marine natural product chemistry in South Africa has not previously been reviewed and so a comprehensive review covering the literature from the 1940's up until the end of 1995 is presented here. The marine ascidian Pseudodistoma species collected in the Tsitsikamma Marine Reserve was shown to contain four new unsaturated amino alcohols [47], [48], [49] and [50] which were isolated as their acetyl derivatives. These compounds exhibited strong antimicrobial activity. Four new pyrroloiminoquinone alkaloids, the tsitsikammamines A [90] to D [93],were isolated from a new genus of Latrunculid sponge collected in the Tsitsikamma Marine Reserve. These highly pigmented compounds also possessed strong antimicrobial activity. An investigation of two phenotypic colour variants of the soft coral Capnella thyrsoidea resulted in the isolation of the known steroid 5α-pregna-1, 20-dien-3-one [97] and an additional six new metabolites, 16β-hydroxy-5α-pregna-1 ,20-dien-3-one 16-acetate [98], 3α,16β-dihydroxy-5α-pregna-1, 20-diene 3,16-diacetate [99] and four xenicane diterpenes, the tsitsixenicins A [100] to D [103]. This is the first reported isolation of xenicane diterpenes from the soft coral family Nephtheiidae. Tsitsixenicin A and B showed good anti-inflammatory activity by inhibiting superoxide production in both rabbit and human cell neutrophils. A further four new metabolites were isolated from two soft corals which could only be identified to the genus level and were designated Alcyonium species A and species B. Alcyonium species A was collected in the Tsitsikamma Marine Reserve and yielded two new polyhydroxysterols, cholest-5-ene-3β, 7β, 19-triol 19-acetate [121] and cholest-5,24-diene-3β, 7β, 19-triol 19-acetate [122]. The soft coral Alcyonium species B was collected off Aliwal Shoal and was found to contain two known xenicane diterpenes, 9-deacetoxy-14, 15-deepoxyxeniculin [110] and zahavin A [16], and two new xenicane diterpenes, 7 -epoxyzahavin A [123] and xeniolide C [124]. Compounds [110], [16] and [123] exhibited strong anti-inflammatory activity and compounds [110] and [16] showed good antithrombotic activity. The endemic soft coral A/cyanium fauri collected at Riet Point near Port Alfred yielded the new sesquiterpene hydroquinone rietone [141] in high yierd, fogether with the minor compounds 8'-acetoxyrietone [142] and 8'-desoxyrietone [143]. Rietone exhibited moderate activity in the NCl's in-vitro anti-HIV bioassays.
- Full Text:
- Date Issued: 1997
Structural studies on some enterobacterial capsular antigens
- Authors: Whittaker, Darryl Vanstone
- Date: 1994
- Subjects: Bacterial antigens -- Analysis Antigens Enterobacteriaceae Escherichia coli Klebsiella
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3803 , http://hdl.handle.net/10962/d1003281
- Description: The investigations presented in this thesis form part of a systematic international effort to establish the structures of the capsules produced by the bacterial genera, Escherichia coli and Klebsiella (family enterobacteriaceae). These bacteria are of medical interest as they are opportunistic pathogens and are frequently responsible for serious infections in animals and man. Invasive strains are invariably surrounded by a structurally complex polysaccharide capsule which contributes to the organism's ability to attenuate non-specific host defence mechanisms or, in some instances, to completely prevent an immune response. A knowledge of the chemical composition and structure of the capsule is, therefore, of great value as it provides insight into the mechanisms involved in this process. The E. coli, in particular, have generated considerable interest as their capsules are more structurally diverse and cross-reactivity with other, more pathogenic bacteria has also been demonstrated. Accordingly, the structures of three previously unstudied E. coli K-antigens viz. those produced by serotypes 020:K83:H26, 020:K84:H26, and 09:K48:H9 have been established by chemical and spectroscopic means and are presented in this thesis. In addition, a reinvestigation of the structure of the capsule produced by Klebsiella K15 using a novel enzymatic approach was also undertaken and a revised structure is proposed . The E. coli K48 polysaccharide is of special interest as it was found to contain a new diacetamido trideoxy hexose hitherto unrecorded. A synthesis for this saccharide is also presented. Finally, the application of lithium dissolved in ethylenediamine for the degradation of amino sugar-containing polysaccharides was also investigated using the capsular polysaccharides produced by E. coli serotypes K38 and K84 as model compounds.
- Full Text:
- Date Issued: 1994
Effect of anticonvulsant agents on pineal gland indole metabolism
- Authors: Morton, Dougal John
- Date: 1983
- Subjects: Pineal gland -- Metabolism Anticonvulsants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3844 , http://hdl.handle.net/10962/d1009518
- Description: Preface: The general indications that the pineal gland might be involved in homeostasis, and more specifically the evidence suggesting a role in amelioration of seizure states warranted further investigation . No reports had examined a possible link between anticonvulsant drug administration and pineal gland function, and few enabled any type of presumption to be made as to possible effects. This study was an attempt to evaluate in which ways anticonvulsant drugs might alter pineal gland indole metabolism, with a view to increasing understanding of the role of the pineal in modulation of epileptic discharges. In order to make the study as meaningful as possible extensive preliminary investigations were necessary. Pharmacokinetic determinations gave an indication of tissue concentrations of the drugs, which could then be related to observed effects. As far as possible, where existing information was lacking, the catalytic behaviour of the various enzymes was characterised in order to explain any observed effects at a molecular level. An attempt was also made to characterise the regulatory mechanisms controlling indole metabolism, again in order to define the pharmacological effects exerted by the drugs used. The complexity of the system made it impossible to suggest a single uniform regulatory hypothesis, although some significant observations were made. Finally, the studies involving the anticonvulsant drugs were conducted on intact animals, isolated organs and individual enzymes in an attempt to determine whether the observed effects were occuring at a molecular, local or central level.
- Full Text:
- Date Issued: 1983
Pharmaceutical analysis and drug interaction studies : African potato (Hypoxis hemerocallidea)
- Authors: Purushothaman Nair, Vipin Devi Prasad
- Date: 2006
- Subjects: Potatoes -- Africa , Potatoes -- Therapeutic use , AIDS (Disease) -- Treatment , HIV infections -- Drug therapy , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3865 , http://hdl.handle.net/10962/d1015802
- Description: In order for a medicinal product to produce a consistent and reliable therapeutic response, it is essential that the final composition of the product is invariable and that the active ingredient/s is/are present in appropriate, non-toxic amounts. However, due to the complexity involved in the standardization of natural products, quality control (QC) criteria and procedures for the registration and market approval of such products are conspicuously absent in most countries around the world. African Potato (AP) is of great medical interest and this particular plant has gained tremendous popularity following the endorsement by the South African Minister of Health as a remedy for HIV/ AIDS patients. Very little information has appeared in the literature to describe methods for the quantitative analysis of hypoxoside, an important component in AP. It has also been claimed that sterols and sterolins present in AP are responsible for its medicinal property but is yet to be proven scientifically. To-date, no QC methods have been reported for the simultaneous quantitative analysis of the combination, β- sitosterol (BSS)/ stigmasterol (STG)/ stigmastanol (STN), purported to be present in preparations containing AP. The effect of concomitant administration of AP and other herbal medicines on the safety and efficacy of conventional medicines has not yet been fully determined. Amongst the objectives of this study was to develop and validate quantitative analytical methods that are suitable for the assay and quality control of plant material, extracts and commercial formulations containing AP. Hypoxoside was isolated from AP and characterized for use as a reference standard for the quality control of AP products and a stability-indicating HPLC/ UV assay method for the quantitative determination of hypoxoside was developed. In addition, a quantitative capillary zone electrophoretic (CZE) method was developed to determine hypoxoside, specifically for its advantages over HPLC. A HPLC method was also developed and validated for the quantitative analysis of BSS, STG and STN in commercially available oral dosage forms containing AP material or extracts thereof. The antioxidant activity of an aqueous extract of lyophilized corms of AP along with hypoxoside and rooperol were investigated. In comparison with the AP extracts and also with hypoxoside, rooperol showed significant antioxidant activity. The capacity of AP, (extracts, formulations, hypoxoside and rooperol as well as sterols to inhibit in vitro metabolism of drug substrates by human cytochrome P450 (CYP) enzymes such as CYP 3A4, 3A5 and CYP19 were investigated. Samples were also assessed for their effect on drug transport proteins such as P-glycoprotein (P-gp). Various extracts of AP, AP formulations, stigmasterol and the norlignans, in particular the aglycone rooperol, exhibited inhibitory effects on CYP 3A4, 3A5 and CYP19 mediated metabolism.These results suggest that concurrent therapy with AP and other medicines, in particular antiretroviral drugs, can have important implications for safety and efficacy. Large discrepancies in marker content between AP products were found. Dissolution testing of AP products was investigated as a QC tool and the results also revealed inconsistencies between different AP products.
- Full Text:
- Date Issued: 2006
A critical evaluation of the human skin blanching assay and comparative bioavailability studies on topical corticosteroid preparations
- Authors: Meyer, Eric
- Date: 1989
- Subjects: Dermatopharmacology Skin, Effect of drugs on Adrenocortical hormones
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3727 , http://hdl.handle.net/10962/d1001464
- Description: Several aspects of the human skin blanching assay were evaluated in an attempt to suggest improvements in the methodology of this assay. Three trials were performed in the unoccluded application mode, using two proprietary creams containing 0,1% betamethasone (as the 17-valerate). Preliminary observations of the influence of ambient temperature and relative humidity on the blanching response did not allow definite conclusions to be drawn. Studies on the number of observers required for reliable results of comparative blanching indicated that at least two trained observers should be employed. Analyses of the results of individual volunteers demonstrated the expected biological variability, and suggest that subjects selected for trials should represent a range of blanching responses. No sex-related differences in blanching responses were found, and both arms exhibited similar sensitivity to corticosteroids. Retrospective analysis of 95 040 observations of blanching responses showed that in the unoccluded application mode blanching is lowest close to the wrist, and in the occluded mode blanching is lowest close to the elbow. Studies on the method of transportation of Betnovate preparations suggest that topical formulations should not be exposed to temperature extremes during transportation. It is proposed that patients should not transport topical formulations in the holds of ships or aircraft, and that exporters and manufacturers should make use of special transportation and storage conditions. In a study of ten topical formulations from three countries it was found that there was no trend of products from one country consistently exhibiting superior blanching to products from the other two countries, or products from one country consistently exhibiting the lowest degree of blanching, although considerable differences in blanching responses were found in some cases. Interpretation of the results of these studies demonstrated the importance of employing a combination of statistical analyses, blanching profiles and AUC values when drawing conclusions regarding comparative bioavailability. A study of the blanching profiles of Betnovate cream included in all 16 trials performed during this work indicated that this preparation behaved in a similar fashion during all trials, thereby giving credence to the results of the trials
- Full Text:
- Date Issued: 1989
A critical realist account of a mentoring programme in the Faculty of Pharmacy at Rhodes University
- Authors: Oltmann, Carmen
- Date: 2009
- Subjects: Rhodes University -- Academic Development Programme Pharmacy -- Study and teaching (Higher) -- South Africa Mentoring in education -- South Africa Mentoring in Science -- South Africa Critical realism Communities of practice
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3781 , http://hdl.handle.net/10962/d1003259
- Description: This study originates from experiences I had as supervisor of the mentoring programme for first year students in the Faculty of Pharmacy, at Rhodes University. Our mentoring programme is a strategy for first year students – specifically those from previously disadvantaged backgrounds – to succeed at Rhodes University. Using an ontological meta-theory - critical realism - as my analytical lens, discourse as my unit of analysis, and Invitational Learning Theory as a theoretical tool I developed a model of mentoring based on Bhaskar’s transformational model (1993). This model illustrates the relationship between structure, culture and agency. Whilst developing this model I focussed on determining how mentors construct mentoring, and how mentoring facilitates access to a Community of Practice (CoP). Mentoring involves providing a shared space that is safe, that the mentor and mentee feel comfortable in, and that supports and challenges both the mentor and the mentee. It is a reciprocal, developmental relationship for both the mentor and the mentee that deals with issues that the mentee deems as ‘real’. Mentoring is a process, not an outcome. The mentoring strategies that the mentors employed changed as the mentors mentored. Mentors help mentees by using structures and mechanisms that worked for them, and/or by helping mentees access these structures and mechanisms. Mentoring facilitates access to a CoP by providing opportunities for engagement. This involves sharing of experiences and knowledge, and promoting discussion. The mentor helps the mentee move from being a peripheral member of the CoP to becoming a main member, i.e., becoming active, learning with and from others within the CoP. CoPs develop social capital and knowledge management. My research suggests that the knowledge, skills and attitude developed by the mentors within this study may be transferable to other aspects in Pharmacy.
- Full Text:
- Date Issued: 2009
Isolation, structural characterisation and evaluation of cytotoxic activity of natural products from selected South African marine red algae
- Authors: Knott, Michael George
- Date: 2012
- Subjects: Marine algae -- South Africa , Red algae -- South Africa , Pharmaceutical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3862 , http://hdl.handle.net/10962/d1015460
- Description: The medicinal chemistry of selected marine algae indigenous to South Africa was investigated. Following the isolation and characterisation of a number of new and known compounds, the associated in vitro cytotoxic profiles of these new compounds was investigated. Plocamium maxillosum yielded two new cyclic polyhalogenated monoterpenes which were characterised as 2E-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.1) and 2Z-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.2) on the basis of one and two dimensional NMR spectroscopic data and MS analysis. These compounds were also found to have good cytotoxic activity against breast cancer cell lines. Although these compounds are based on a regular monoterpene skeleton, they represent an uncommon feature not often seen in cyclic halogenated monoterpenes from marine algae. Plocamium robertiae yielded one new cyclic polyhalogenated monoterpene identified as 4,5- dibromo-5-chloromethyl-1-chlorovinyl-2-chloro-methylcyclohexane (2.6) and one known compound called 2,4-dichloro-1-chlorovinyl-1-methylcyclohexane-5-ene or Plocamene D (2.9). Portieria hornemannii was collected from Port Edward in Natal and yielded three new compounds, namely; 3Z-1,6-dibromo-3-(bromomethylidene)-2,7-dichloro-7-methyloctane (3.1), 1E,3Z-1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.2), 1Z,3Z- 1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.3), and one known compound, namely; 3S,6R-6-bromo-3-(bromomethyl)-3,7-dichloro-7-methyloct-1-ene (3.4). Compounds 3.1 and 3.2 showed no cytotoxic activity against breast cancer cells. Another Portieria hornemannii sample was collected from Noordhoek in the Eastern Cape, it yielded one known compound referred to as 3Z-6-bromo-3-(bromomethylidene)-2,7- dichloro-7-methyloct-1-ene (3.5), as well as one new compound called portieric acid A (3.6) or 5-bromo-2-(bromomethylidene)-6-chloro-6-methylheptanoic acid. Portieric acid A showed slight cytotoxic activity and also represents a new class of compound within the genus Portieria. The isolation of secondary metabolites from the South African red alga, Laurencia glomerata, yielded two known compounds; 7-hydroxylaurene (4.9) and cis-neolaurencenyne (4.12), as well as one chamigrane related compound (4.11). Laurencia flexuosa yielded one known compound called 3Z-bromofucin (4.13). Using 1H NMR, GC and molecular systematics, a novel method for identifying different species of Laurencia was also investigated.
- Full Text:
- Date Issued: 2012
Pharmaceutical analysis and quality of complementary medicines : sceletium and associated products
- Authors: Patnala, Satya Siva Rama Ranganath Srinivas
- Date: 2007
- Subjects: Alternative medicine , Herbs -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3872 , http://hdl.handle.net/10962/d1018263
- Description: There has been an upsurge in the use of Complementary and Alternate Medicines (CAMs) in both developed and developing countries. Although herbal medicines have been in use for many centuries, their quality, safety and efficacy are still of major concern. Many countries are in the process of integrating CAMs into conventional health care systems based on the knowledge and use of traditional medicines. The quality control (QC) of herbal products usually presents a formidable analytical challenge in view of the complexity of the constituents in plant material and the commercial non-availability of appropriate qualified reference standards. Sceletium, a genus belonging to the family Aizoaceae, has been reported to contain psychoactive alkaloids, specifically mesembrine, mesembrenone, mesembrenol and some other related alkaloids. Sceletium is marketed as dried plant powder and as phyto-pharmaceutical dosage forms. Sceletium products and plant material marketed through health shops and on the internet are associated with unjustified claims of specific therapeutic efficacy and may be of dubious quality. Validated analytical methods to estimate Sceletium alkaloids have not previously been reported in the scientific literature and the available methods have focused only on qualitative estimation. Furthermore, since appropriate markers were not commercially available for use as reference standards, a primary objective of this study was to isolate relevant compounds, qualify them as reference standards which could be applied to develop appropriate validated qualitative and quantitative analytical methods for fingerprinting and assay of Sceletium plant material and dosage forms. The alkaloidal markers mesembrine, mesembrenone and ∆⁷ mesembrenone were isolated by solvent extraction and chromatography from dried plant material. Mesembranol and epimesembranol were synthesised by hydrogenation of the isolated mesembrine using the catalyst platinum (IV) oxide and then further purified by semi-preparative column chromatography. All compounds were subjected to analysis by ¹H, ¹³C, 2-D nuclear magnetic resonance and liquid chromatography-tandem mass spectroscopy. Mesembrine was converted to hydrochloride crystals and mesembranol was isolated as crystals from the hydrogenation reaction mass. These compounds were analysed and characterised by X-ray crystallography. A relatively simple HPLC method for the separation and quantitative analysis of five relevant alkaloidal components in Sceletium was developed and validated. The method was applied to determine the alkaloids in plant material and dosage forms containing Sceletium. An LCMS method developed during the study provided accurate identification of the five relevant Sceletium alkaloids. The method was applied for the quantitative analysis and QC of Sceletium plant material and its dosage forms. This LCMS method was found to efficiently ionize the relevant alkaloidal markers in order to facilitate their detection, identification and quantification in Sceletium plant material as well as for the assay and QC of dosage forms containing Sceletium. The chemotaxonomy of some Sceletium species and commercially available Sceletium dosage forms were successfully studied by the LCMS method. The HPLC and LCMS methods were also used to monitor the bio-conversion of some of the alkaloids while processing the plant material as per traditional method of fermentation. Additionally a high resolution CZE method was developed for the separation of several Sceletium alkaloids in relatively short analysis times. This analytical method was used successfully to fingerprint the alkaloids and quantify mesembrine in Sceletium and its products. Sceletium species grown under varying conditions at different locations, when analyzed, showed major differences in their composition of alkaloids and an enormous difference was found to exist between the various species with respect to the presence and content of alkaloids. Sceletium and its products marketed through health shops and the internet may thus have problems with respect to the quality and related therapeutic efficacy. The QC of Sceletium presents a formidable challenge as Sceletium plants and products contain a complex mixture of compounds. The work presented herein contributes to a growing body of scientific knowledge to improve the QC standards of herbal medicines and also to provide vital information regarding the selection of plant species and information on the specific alkaloidal constituents to the cultivators of Sceletium and the manufacturers of its products.
- Full Text:
- Date Issued: 2007