No description available.

No description available.

No description available.

No description available.

No description available.

Using the Scanning Electron Microscope (SEM), fruit surface and pericarp anatomy were investigated in the African species of Bolboschoenits (Ascherson) Palla [B. maritimus (L.) Palla; B. glaucus (Lam.) S.G. Smith; B. nobilis (Ridley) Goetghebeur & D.A. Simpson; B. grandispicus (Steud.) K. Lewejohann & W. Lobin] and extended worldwide to cover most known species. There was consideration of type specimens wherever possible. Two main patterns of pericarp construction were revealed, with modifications. Using fruit samples from field populations, a surveillance of embryos was carried out to gain some information on percentages of perfect embryo development and variability in embryo outline (as seen in optical, median sagittal section), within and between selected species. Inflorescence structure within African species was studied and illustrated photographically and diagrammatically. The collective information obtained was directed towards better understanding of species limits within the genus and towards gaining evidence of the significance of natural hybridisation as a cause of morphological variability within some taxa. Formal taxonomy including a key to the identification of the African species is provided. Profuse illustrations of pericarp structure of world species are given, as are colour photographs of the African species, excepting B. grandispicus. A tentative pattern for subgeneric division of Bolboschoenus based primarily on pericarp morphology, is suggested supplemented by a world map illustrating the presently known distribution of the suggested groupings. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1998.

This study extends an earlier M.Sc. research project on the narrow-leaved species of the genus Asclepias L. (30 species) to cover the entire subtribe Asclepiadinae sensu K. Schum. in southern Africa- (182 species in 23 genera). Two genera (Eustegia R. Br. and Pentarrhinum E. Mey.) are revised and then removed from this tribe. The remaining 177 species and 21 genera form the focus of this thesis, whose principal objectives are to reevaluate the taxonomic and evolutionary significance of various macro, micro and chemical characters and then use them to produce a classification that, more closely, reflects the overall similarity and phylogeny of the taxa involved. Species and genera are recircumscribed based on the wealth of data that has come to light since the subtribe was last revised by N.E. Brown (1907-1908) some 90 years ago. This process was supplemented by extensive field work, observations on pollination and reproductive biology, ecology, biogeography, conservation and ethnobotany. The majority of this thesis consists of a compilation of 17 papers, 12 of these published and most, but not all, of the remainder in preparation for press. Two of these papers form the bulk of the taxonomy. The first deals with what was the genus Asclepias in southern Africa. The genus is now believed to be confined to the Americas. The • Botswana, Lesotho, Namibia, South Africa and Swaziland. southern African species have diverse origins and are partitioned into 7 genera, one of them (Gomphocarpus R. Br.) resurrected, two of them (Aidomene Stopp and Aspidonepsis Nicholas & Goyder) expanded and four of them (Paulforstera, Sigridia, Bruynsia and Pachyacris) described as new. Gomphocarpus is divided into two subgenera and Aidomene into four subgenera. Three new species are also described. The second paper investigates the bulk of most of the remaining genera. Kanahia R. Br., Cordylogyne E. Mey. and Fanninia Harv. remain as is. Xysmalobium R. Br., previously a genus of 19 species in southern Africa, is reduced to three species in two subgenera. Trichocodon is segregated off from Pachycarpus E. Mey. as a new genus. While two species, previously placed in Xysmalobium, are added to Pachycarpus, but placed in the new subgenus Parapodiopsis. Parapodium E. Mey. is reduced from three to two species and Periglossum Decne. is reduced from five to three species, one of them newly described. Woodia Schltr. and Stenostelma Schltr. are both considerably expanded, mainly with species previously housed in Xysmalobium), and the former divided into two subgenera. The third paper briefly looks at the Schizoglossum E. Mey., Miraglossum Kupicha and Aspidoglossum E. Mey. Some changes are suggested but, as further work is needed, none are formalised. As a corollary to the taxonomy, secondary metabolite profiles of 38 species and 17 genera were done using Thin layer Chromatography. The results sometimes confirmed morphological patterns and sometimes were at odds with them. A trend from simple profiles to more complex profiles seems to echo the suspected phylogeny of the genera within this sub tribe. Some species and genera have greater chemical diversity than others and secondary metabolites are shown to vary considerably in different parts of a single plant. As a supplement to the above work or because they are cited elsewhere in the dissertation, published papers dealing with floral structure, the asclepiadaceous work of Rudolf Schlechter, as well as miscellaneous works in the tribe Stapelieae, are also given. / Thesis (Ph.D.)-University of Durban-Westville, 1999.

The majority of the population in South Africa use traditional health care to treat various mental conditions. This thesis has two main objectives; to bring together a comprehensive and detailed record of psychotropic plants used in southern Africa by indigenous peoples for medicinal or cultural purposes. Secondly, this research attempts to investigate the validity and rationale of the use of these plants by screening them in various biological assays for psychotropic activity. Plants were selected, based on their traditional use and availability, and were screened in four assays, which detect biological activity of a useful nature. A number of in vitro enzymatic and neuronal signal transduction assays were employed in this thesis, the inhibition of the serotonin reuptake transporter protein (SERT); inhibition of catabolic enzymes (e.g. acetylcholinesterase, monoamine oxidase); GABAA- benzodiazepine receptor binding. The influence of legislation, past and present, on the state of traditional medicine is highlighted. Aspects of the philosophies and practises of the various practitioners of South African traditional medicine will be discussed. An annotated list compiled from available ethnobotanical literature of plants traditionally used for central nervous system-related purposes is provided. It contains more than 330 species, from 94 families, which are currently used or have been used for cultural, medicinal and recreational purposes related to the central nervous system (CNS). Where available, information pertaining to plant part used, preparation method, dosage, route of administration, known and potentially active constituents are included. Seventy five extracts from 34 indigenous plant species used in South African traditional medicine or taxonomically related to these were investigated for their affinity to the serotonin reuptake transport protein, making use of an in vitro [3H]-citalopram serotonin reuptake transport protein binding assay. Aqueous and 70% ethanolic extracts of various plant parts were screened and 45 extracts derived from 15 plant species showed affinity. The affinity of 12 extracts from four plants was characterized as high (more than 50% inhibition at 5, 1, and 0.5 mg/ml). Plant species with high affinity to the serotonin reuptake transport protein included Agapanthus campanulatus, Boophone disticha, Datura ferox and Xysmalobium undulatum. Agapanthus campanulatus yielded high activity in aqueous extracts from leaves and flowers. B. disticha showed high activity both in aqueous and ethanolic extracts of leaves and bulbs. D. ferox showed high activity in aqueous extracts from the seeds and X. undulatum showed high activity in the ethanolic extract of the whole plant. Two compounds, buphanadrine and buphanamine, were isolated by bioassay-guided fractionation on vacuum-liquid-chromatography (VLC) and preparative thin-layer-chromatography (TLC) from B. disticha. The structures of the compounds were determined by 1H and 13C NMR. Fractions were tested for affinity to the serotonin transporter in a binding assay using [3H]-citalopram as a ligand. The IC50 values of buphanidrine and buphanamine were 274 ìM (Ki = 132 ìM) and 1799 ìM (Ki = 868 ìM), respectively. The two alkaloids were also tested for affinity to the 5HT1A receptor, but only showed slight affinity. Aqueous and ethanol extracts of 43 plants that are traditionally used to treat against epilepsy and convulsions were initially tested in the GABAA-benzodiazepine receptor binding assay, where the binding of 3H-Ro 15-1788 (flumazenil) to the benzodiazepine site is measured. The GABAA-benzodiazepine receptor complex is involved in epilepsy and convulsions. Out of the 118 extracts tested, one aqueous and 18 ethanol extracts showed activity. The most active extracts were the ethanolic leaf extracts of Searsia tridentata, Searsia rehmanniana and Hoslundia opposita and the ethanolic corm extract of Hypoxis colchicifolia, which all showed good dose-dependent activity. A further forty-six ethanol extracts from another 35 species, both indigenous and exotic that are traditionally used predominantly as sedatives or to treat various CNS-related ailments were tested in the GABAA-benzodiazepine receptor-binding assay. Out of the 46 extracts tested, seven showed good activity and 10 showed moderate activity. The most active extracts were the ethanolic leaf extracts of Arctopus echinatus, Artemisa afra, four Helichrysum species and Mentha aquatica which all showed good dose-dependent activity. Two biflavonoids with activity in the 3H-Ro 15-1788 (flumazenil) binding assay were isolated by high pressure liquid chromatography (HPLC) fractionation of the ethanol extract of the leaves from Searsia pyroides. The structures of the two biflavonoids were elucidated by nuclear magnetic resonance spectroscopy (NMR) to be agathisflavone and amentoflavone. Agathisflavone and amentoflavone competitively inhibited the binding of 3H-Ro 15-1788 with a Ki of 28 and 37 nM, respectively. Extracts of Searsia dentata and Searsia pentheri were not as active as the extract from Searsia pyroides; both were found to contain apigenin and agathisflavone. The monomer apigenin, agathisflavone and amentoflavone were fitted into a pharmacophore model for ligands binding to the GABAA receptor benzodiazepine site. This reflected the affinities of the compounds in the [3H]-flumazenil binding assay. Mentha aquatica, a mint that is found in Europe and Africa, is used in Zulu traditional medicine for spiritual purposes. The ethanolic leaf extract showed a strong affinity to the GABA-benzodiazepine receptor. Viridiflorol from the essential oil and (S)-naringenin from an ethanolic extract was isolated by bioassay-guided fractionation using binding to the GABA-benzodiazepine site. Viridiflorol had an IC50 of 0.19 M and (S)-naringenin of 0.0026 M. Twenty plants used in Zulu traditional medicine for several CNS-related ailments were screened for MAO inhibition and specific MAO-B inhibition activity. MAO-B inhibitors are currently employed in the treatment of neurodegenerative related illnesses such as Parkinson's and Alzheimer's diseases. A photometric peroxidase linked assay was used to determine the inhibition of the oxidative deamination of tyramine by MAO isolated from rat liver. Ruta graveolens exhibited the best MAO inhibitory activity (ethyl acetate leaf extract = IC50 5 ± 1 ìg/ml, petroleum ether extract = 3 ± 1 ìg/ml) and specific MAO-B inhibition (ethyl acetate leaf extract = IC50 7 ± 6 ìg/ml petroleum ether extract = 3 ± 1 ìg/ml). Schotia brachypetala, Mentha aquatica and Gasteria croucheri also exhibited good MAO-B inhibition activity. Six extracts of varying polarity of Mentha aquatica were tested in a photometric peroxidase linked MAO bioassay. The 70% ethanol extract had highest inhibitory activity. (S)-Naringenin was isolated from the extract by bioassay guided fractionation on VLC and preparative TLC. The structure of the compound was determined by 1H, 13C and 13C-DEPT NMR and optical rotation. The IC50 values for MAO inhibition by naringenin were 342 ± 33 ìM for the rat liver mitochondrial fraction, 955 ± 129 ìM for MAO-A and 288 ± 18 ìM for MAO-B respectively. South African traditional medicine clearly utilizes many botanical species with CNS-related activity. Only a small number of the more than 330 southern African plant species reported to treat or alter the CNS have been scientifically evaluated. To date very few of the active compounds have been isolated and identified. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

The cancer bush (Lessertia frutescens L.) is an important leguminous perennial native to southern Africa and has been used for centuries in traditional medicine by the continent’s diverse cultural groups. Like many other legumes, the seeds of this species exhibit dormancy. Moreover, woody plants are typically difficult to propagate in in vitro culture systems. But in vitro shoot cultures are valuable in providing an alternative means of deriving desired secondary metabolites or phytocompounds, under controlled conditions. This study describes novel protocols for breaking seed dormancy, rapid and efficient in vitro propagation, bioreactor culture, and comprehensive phytochemical data following screening and analysis of in vitro and field extracts of L. frutescens. Experiments using physical, mechanical and chemical pre-sowing treatments were conducted to determine the germination response of this species. The results indicated that seeds of L. frutescens exhibited exogenous dormancy due to the inhibitory effect of the hard coat on germination. Seed dormancy was released by mechanical scarification in which 100 % germination was achieved. In vitro propagation studies using single node explants in Murashige and Skoog (MS) medium supplemented with combinations of different concentrations of benzyladenine and naphthaleneacetic acid revealed a maximum number of 10 shoots per explant in solid medium, and 12.9 shoots per explant in liquid medium inside a temporary immersion bioreactor. Indirect shoot organogenesis and plant regeneration using rachis and stem segments was achieved with the highest percentage of explants forming shoots (88.8 %) from rachis explants cultured onto MS medium supplemented with thidiazuron. Direct shoot organogenesis from hypocotyl and cotyledon segments was also achieved in L. frutescens. The highest shoot regeneration using hypocotyls (83 %) was obtained in MS medium supplemented with kinetin whilst the highest shoot regeneration using cotyledons (46 %) was obtained in MS medium supplemented with kinetin in combination with benzyladenine. Successful rooting (up to 80 %) and acclimatization (up to 90 % survival rate) was attained. Spectrophotometric and gravimetric methods indicated that saponins were the most abundant, followed by phenolics, flavonoids and then alkaloids in in vitro leaf extracts then in field leaf extracts and seed extracts, respectively. After qualitative analysis these extracts were also found to contain tannins, phlobatannins and cardiac glycosides of medicinal interest. By using gas and liquid chromatography the presence of the medicinally important L-canavanine, gamma amino-butyric acid and D-pinitol was verified in in vitro leaf, field leaf and seed extracts. In vitro leaves had higher quantities of all compounds, except for D-pinitol. Phytocompound analysis of shoots derived from several of the cytokinin-enhanced media showed that these organs contained higher quantities of L-canavanine compared to the control. This study, therefore, highlights the potential techno-economic production of medicinal phytocompounds from in vitro leaves of L. frutescens following large scale production using the protocols described in this study. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2011.

No abstract available. / Thesis(Ph.D.)-University of Durban-Westville, 1996.