D.Phil. / The objective of the research described in the first part of this thesis was to develop a general method utilising palladium catalysed reactions for the synthesis of the anti-cancer compound, lavendamycin and analogs thereof. Therefore, the development of a general route to synthetic euivalents of the lavendamycin AB quinoline system, 2-hydroxyquinolines, with potential for coupling to the CDE or CD moiety, was addressed. The first protocol for the synthesis of 2-hydroxyquinolines invloved to the use of appropriately substituted o-nitrophenyltriflates (readily prepared from phenols) in a Heck reaction under neutral conditions followed by a one-pot reduction and cyclisation step. The synthetic potential of such an approach was demonstrated by the preparation of a suitable lavendamycin AB synthon from commecially avalaible guiacol. A second general strategy towards the synthesis of the AB synthon utilising a performed ring system commecially available 8-hydroxyquinoline has been successfully developed. This approach requiring the introduction of a suitable leaving group in the 2-position involved the following sequence of reactions: protection of 8-hydroxyl group N-oxidation, and a rearrangement step. This methodology yielded five different key intermediates all possessing suitable functionality in the 2 position which would allow further cross-coupling to an appropriate CDE ring equivalent.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Plant Physiology))--University of Pretoria, 2005. / Plant Science / unrestricted

Magister Scientiae - MSc / Early man dabbled with the use of plant extracts to cure ailments. This practice has been passed down from generation to generation and today more than 50% of the world'sdrugs are natural products or derivatives thereof. Scientists have thus established a branch of research called natural product research. This branch of research involves the identification and purification of secondary metabolites with a specific biological activity. The methodology involves the screening of plant products for a specific biological activity, purification of the biologically active natural product by separation technology and structure determination. The biologically active natural products is then further scrutinized to serve as a novel drug or lead compound for the development of a novel drug. This research exploited this research methodology. / South Africa

Magister Pharmaceuticae - MPharm / Hypertension is by far the most common risk factor for cardiovascular disease (CVD), which has been identified as the leading cause of death worldwide and a major economic burden in developing countries. Over the years, there has been an increased interest in isolating and identifying bioactive compounds from medicinal plant, with the aim of finding alternative sources of therapy to some of the problematic synthetic drugs and to validate the therapeutic use of some traditional plants. The renin angiotensin aldosterone system is a key regulator of blood pressure, on which ACE (Angiotensin Converting Enzyme) inhibitors act and have been at the forefront of therapeutic strategy for treatment and management of hypertension and CVD. But despite the success of ACEI’s, their long term use has been associated with side- effects coupled with its contraindication in pregnancy. The plant of interest, Centella asiatica is a widely known medicinal plant, used in treatment of a variety of conditions including hypertension. There is currently no scientific evidence validating its claimed use in hypertension. This study therefore, investigated the ACE inhibitory effects of Centella asiatica. Crude methanol, ethanol and aqueous extracts of Centella asiatica were assayed for ACE inhibition activity. Methanol and ethanol crude extract(s) was subjected to a bioassay guided fractionation process to isolate and identify the active compounds. A fluorescence based ACE assay was utilized at various stages of the process including HPLC purification stage to screen the fractions and compounds for ACE inhibition activity.

Philosophiae Doctor - PhD / Actinobacteria, a Gram-positive phylum of bacteria found in both terrestrial and aquatic environments, are well-known producers of antibiotics and other bioactive compounds. The isolation of actinobacteria from unique environments has resulted in the discovery of new antibiotic compounds that can be used by the pharmaceutical industry. In this study, the fynbos biome was identified as one of these unique habitats due to its rich plant diversity that hosts over 8500 different plant species, including many medicinal plants. In this study two medicinal plants from the fynbos biome were identified as unique environments for the discovery of bioactive actinobacteria, Aloe ferox (Cape aloe) and Sutherlandia frutescens (cancer bush).

Athrixia phylicoides (bush tea) is one of many plants from the Asteraceae family used as a traditional herbal medicine. With very few cultivated plants, natural growing plants currently serve as the main resource for plant material. The plant is not yet commercialised and its medicinal value is known and used only by a few people. With the long term aim at commercial scale propagation, this study consists of three parts. Firstly we developed a protocol for in vitro propagation of A. phylicoides. Secondly, the ultrastructure and morphology of leaves were studied microscopically and thirdly, comparisons were made between in vitro and ex vitro grown plants. Nodal segments of greenhouse plants were used to establish cultures. Better growth and less wilting was recorded on explants surface sterilised with NaOCl compared to Ca(OCl)2 after establishment. The addition of growth regulators IBA (indole-3-butyric acid) and BAP (6-benzylaminopurine) to the culture medium did not seem to affect the growth response of explants during the multiplication phase. Hyperhydricity was a problem throughout our trials. The development of hyperhydricity symptoms seems to be related to seasonal changes in the stock plant material used to initiate cultures, rather than the composition of growth medium or growth room temperatures. The occurrences of hyperhydricity symptoms were inconsistent and unpredictable. A rooting medium with added BAP and decreased sucrose levels resulted in a higher rooting percentage compared to the control medium, free from BAP and with a higher sucrose concentration, which yielded no rooting. However, in another experiment, in vitro rooting occurred spontaneously after subdividing and transfer of microshoots to fresh control medium. The addition of GA3 to the establishment medium (but not to the subsequently used multiplication and rooting media) yielded a slightly higher percentage of rooting. However, cultures initially established on GA3 medium yielded fewer roots per explant and roots were shorter than those of explants established on hormone free medium. The medicinal properties of plants are often linked to the production of essential oils. We hypothesised that the medicinal value of A. phylicoides can be linked to the production of the aromatic essential oils released by leaves. A microscopic study of leaves provided some preliminary insight of the mechanisms involved in the production of medicinally active products. Electron- and light microscopic examination of leaves were used to identify and study structures that are apparently involved in the production and secretion of essential oils. Two types of trichomes were identifyed – nonglandular and glandular trichomes. These glandular trichomes are multicellular with a subcuticular storage space and are present only on the adaxial surface of leaves. In the case of medicinal plants, it is essential that the medicinal properties of the plant are not altered by the method of propagation. This was our motivation for comparing the morphology and ultrastructure of leaves of plants that were grown in their natural environment to that of plants grown in vitro. Leaf surfaces of in vitro grown plants were smaller and the number of glandular trichomes per surface area was less on in vitro grown plants. There were no noticeable changes in the morphology of glandular trichomes. / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Plant Production and Soil Science / unrestricted

Morindae Officinalis Radix (MOR), Bajitian in Chinese, is the dried root of Morinda officinalis F.C.How. (Rubiaceae). It is one of the most popular herbal medicines used in the southeast region of China. Various types of chemical constituents have been experimentally shown to be bioactive components of MOR, among which secondary metabolites and saccharides predominate. Pharmacological studies revealed MOR shows kidney tonifying, anti- osteoporosis, antidepressant, anti-inflammatory and antioxidant effect. Since 2002, MOR has been approved as a food supplement for daily healthcare, hence increasing consumption and demand for better quality of MOR. However, selection of MOR with superior quality is largely based on traditional experience which lacks scientific basis. For example, 3-4-year-old MOR is usually used without xylem; and processed MOR are believed to show different bioactivities. Therefore, to promote the rational utilization and ensure efficacy of MOR, overall qualitative and quantitative characterization of MOR in different traditional usage is needed. Anthraquinones, iridoid glycosides and oligosaccharides are the common reference compounds for chemical characterization of MOR. However, they are usually selectively characterized, which is not comprehensive enough in herbal quality evaluation. To deal with this, metabolomics targeting secondary metabolome and glycomics targeting glycome can be applied. And the integration of metabolomics and glycomics could be a promising approach to investigate overall chemical variations in MOR according to its traditional usage. Therefore, in this study, chromatographic methods for metabololmics and glycomics were firstly developed to study the traditional usage of MOR. In Chapter 2, they were applied for studying chemical variation and differences in growth year and plant tissue of MOR. In Chapter 3, chemical differences in processed products of MOR were also studied using the established metabololmics and glycomics methods. Further bioactivity differences of them were studied by cell metabolomics with HEK 293 cells under high glucose microenvironment. Besides that, in Chapter 4, consumption method of not only MOR, but other herbal medicines were studied. Conventional boiling water extraction (BWE) and ultrasound-assisted extraction (UAE) were compared to understand their effects on polysaccharides. For the study of growth year and tissues of MOR, the results showed that various types of bioactive components reached a maximum between 3-4 years of growth; and that xylem contained more potentially toxic constituents, but less bioactive components, than cortex. For the study of processing products, the results showed that secondary metabolome and glycome of raw MOR and other processing products was found qualitatively and quantitatively different. Contents of secondary metabolites were generally increased in processed products, while saccharides were decreased instead. Also, steamed MOR (F) seemed to show preventive effect of diabetic nephropathy and different MOR processing products had induced different metabolic changes on high glucose induced HEK 293 cells. In the study of extraction methods, the results showed that the polysaccharides from the herbal medicines by UAE were quantitatively and qualitatively different with those by BWE. The powerful extraction ability and polysaccharide degradation caused by ultrasound collectively contributed to these differences. It was revealed that not only the UAE conditions but also the polysaccharide structures could affect the extraction ability and polysaccharide degradation To conclude, metabolomics and glycomics were integrated in this study to investigate the variations in secondary metabolome and glycome in MOR. We had successfully applied these methods to study and provide scientific basis for traditional practice of MOR. We had proved that 3rd to 4th years of growth are the key period for the development of the biochemical signature of MOR. Xylem and cortex of MOR were qualitatively and quantitatively different and removing xylem could help to remove potentially toxic components. This study also provided scientific evidences for the justification of MOR and its processed products, as well as their metabolic effects on high glucose induced DN in HEK 293 cells. Besides, this study revealed both UAE parameters and structural properties of polysaccharides affects extraction recovery of polysaccharides in herbal medicines. Hence, we suggest UAE should be carefully considered before employing it in relevant chemical and pharmacological analysis.

In this thesis, I focused mainly on orchids and also carried out some research on different pharmaceutically potential plants in Nepal. I compiled both data from field and secondary data sources and one of my first outputs was complete checklist of orchids in Nepal. I also studied distribution patterns and affinities of orchids with different floristic regions in Nepal. My next work on epiphytic orchids is related to diversity, distribution and host- species associations and their future in the context of climate change in Nepal. In addition to this, I also worked on factors affecting epiphytic orchids along an altitudinal gradient in central Nepal. Working on population dynamics of terrestrial orchid species, Crepidium acuminatum, lasted for 6 years. Together with orchids, I determined secondary compounds present in a highly important Nepal endemic medicinal plant, Swertia multicaulis. I also compiled the information on uses, phytochemistry, pharmacology and toxicity of highly important Himalayan endemic medicinal plant, Neopicrorhiza scrophulariiflora. The last research of my Ph.D. project ended up by gathering the information on uses of different medicinal plants, including orchids that were used to treat various gastrointestinal diseases in Nepal. The results of my doctoral thesis are presented...

Abstract available on the file 00front / Thesis (PhD (Plant Production and Soil Science))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

Philosophiae Doctor - PhD / This thesis was informed by what I perceived to be a tense relationship between Western biomedical science and, for example, “traditional” or “indigenous” ways of producing knowledge about medicinal plants used to manage a pervasive condition like Tuberculosis (TB) in South Africa. Hoping to reimagine this relationship and its possibilities, I follow medicinal plants collected from Genadendal through three research spaces with disparate but intertwined knowledge heritages to investigate these tensions but also to tease out how knowledge about locally used medicinal plants is generated and “done” in practice. The first space was at the South African Herbal Science and Medicines Institute (SAHMI) as part of an experiential science project led by scientists who were interested in studying medicinal plants which could potentially provide new sources of safe, affordable, and sustainable medicine for communicable conditions such as TB.