In this study two medicinal plant species, namely Artemisia afra Jacq. ex. Willd and Elytropappus rhinocerotis Less. (L.f) (= Dicerotamnus rhinocerotis Koekemoer), both belonging to the family Asteraceae, have been investigated and different compounds isolated and characterised. Both species are important plants used in traditional medicine in general in Africa and particularly in South Africa. A. afra, commonly called "African wormwood" is one of 400 species belonging to the genus Artemisia and it is the only one indigenous to Africa. E. rhinocerotis is one of eight Elytropappus species which are all restricted to the Cape floristic region. The aim of this study was to investigate the phytochemistry of these species. In total fifteen compounds were isolated and characterised. From the E. rhinocerotis extract, four known compounds, labdanolic acid, methyl labdanolate, 6, 7- dimethoxycoumarin and a sesquiterpene viridiflorol were isolated. These compounds were not previously reported from E. rhinocerotis. Two different chemotypes of A. afra were studied and eleven compounds were isolated. These compounds include sesquiterpenes such as taurin, artesin, maritimin, artemin, norsantolinifolide, santolinifolide A, and reynosin, a flavonoid, 5- hydroxy-7,4-dimethoxyflavone, a coumarin called scopoletin or 7-hydroxy-6- methoxycoumarin and other aromatic compounds such as p-hydroxyacetophenone, and 2,4-dihydroxy-6-methoxyacetophenone. Except for taurin, scopoletin and 5-hydroxy-7, 4- dimethoxyflavone , none of these other compounds has been reported previously from A. afra. This study has shown that A. afra contains a large number of sesquiterpenoids, mostly from the eudesmane-type. Structural elucidation of different compounds was performed using mainly NMR spectroscopy. Other methods used for identification include LC-MS and infrared spectroscopy. The major compound, labdanolic acid, is known to selectively inhibit cyclooxygenase-2, an enzyme associated with inflammation. The presence of labdanolic acid in the plant may account for its traditional use as an anti-inflammatory. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

M.Sc. (Botany) / The genus Lessertia DC. consists of 54 species of papilionoid legumes. The species have imparipinnate leaves, paired stipules, sub-capitate or elongate racemes and compressed or inflated legumes. The closest relative of the genus is Sutherlandia R. Br. ex W. T.Aiton, which differs in having a very large, bird-pollinated flower, a standard which is smaller than the keel, a long ovary stipe and a very large, much inflated legume. The last comprehensive revision of Lessertia was done by Harvey (1862), where 30 species were recognized. Harvey concluded that the species were difficult to define. This study was therefore initiated to evaluate characters of possible taxonomic value so that the circumscription and identification of species can be facilitated. More than 1000 specimens from different herbaria were examined to study morphological characters such as habit, indumentum, leaves and leaflets, flowers and flowering times, fruits, habitat and distribution of the species. Flowers of all the species were dissected and flower parts were drawn using camera lucida. Flower characters such as the length, width and vestiture of the petals were studied. For flavonoids and terpenoids, 17 species of Lessertia were sampled for a pilot study to compare chemical compounds between the species. The ethnobotanical literature was reviewed in order to compile a list of all the species of value in traditional medicine. Vegetative characters are often not species-specific but they can be used to distinguish between some closely related species, either as single characters or as combinations of characters. Further details can be seen in the keys presented in this study.

M Tech. (Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Rhus leptodictya commonly known as a mountain karee belongs to the family Anacadeceae and has been used since antiquity in tradition medicine. In the present study antimicrobial and antioxidant potentials of the leaves of Rhus leptodictya were studied, followed by isolation of at least one active compound which showed antibacterial and antioxidant potentials. Extractions were performed based on the polarity of the solvent used. The solvents used were hexane, dichloromethane, ethyl acetate, acetone and methanol. Dichloromethane was found to be extracting more compounds than the other used solvents. Thin layer chromatography (TLC) was used to determine the chemical composition of the extracts by employing different solvent systems. The results showed that, of the solvent systems used, namely ethyl acetate: methanol: water (EMW) 40: 5: 1; chloroform: ethyl acetate: formic acid (CEF) 5: 4: 1 and benzene: ethanol: ammonium hydroxide (BEA) 90:10:1, BEA produced better separations. To determine the antioxidant potential of the leaves, 2.2-diphenyl picrylhydrazyl (DPPH) was used. Different spot with different Rf values were found to be active by show of yellow colour on the TLC plate. The yellow colour is due to the proton gained by DPPH when it reacts with active compound. Bioutography results showed that different leaves were active against selected bacterium. Minimum inhibitory concentration studies showed that the methanol extract was more active against B.subtilis and S.pnuemonia at concentration less than 0.1 mg/ml respectively. Dichloromethane extract was found to be the least effective on S.pneumonia, as compared to the methanol, acetone and ethyl acetate extracts. In terms of the total activity, the ethyl acetate concentration showed better total activity than the other extracts studied in this research. A new compound 7, 8-trihydroxy-2-(4’hydroxy phenyl)-3-5-[5’’, 6’’-dihydroxy-2’’-O-(4’’’hydroxyphenyl)-4-1t-chromen-4’’-one]-41t-chromen-4-one was isolated and characterized by H1-NMR, C13-NMR, MS and IR. According to the literature search, this compound has never been isolated from any plant and it has showed both antioxidant and antibacterial activity.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Horticulture in the Faculty of Applied Sciences at the Cape Peninsula University of Technology / The high demand for medicinal plants has favoured over-exploitation of wild plants. The search for alternative and sustainable methods of medicinal plant cultivation is imperative and desirable. Biotechnological approaches particularly hydroponic technology has the potential for large scale plant cultivation and production of secondary metabolites. The current study aims at optimizing the production of antimicrobial secondary metabolites by an indigenous South African medicinal plant species (Helichrysum cymosum) through hydroponics N and K fertilization. In Chapter 1, the conceptual framework and justifications of the study are presented. In Chapter 2 the research objective was to discern the optimal potassium (K) supplement level for H. cymosum by evaluating the effects of different hydroponic K levels on growth, K-leaf content, and anti-Fusarium oxysporum f.sp.glycines (Ascomycota: Hypocreales) and total activities. Six weeks old seedlings of H. cymosum were treated with varied concentrations of K in the form of potassium chloride, potassium nitrate and monopotassium phosphate (58.75, 117.5, 235 and 470 ppm). These concentrations were based on a modification of Hoagland’s hydroponic nutrient formula. Plants were maintained under greenhouse conditions and growth parameters (plant height and number of leaves) were recorded weekly. At 8 weeks post treatment, plants were harvested and fresh weights were recorded and tissue nutrient content analysed. Sub-samples of the aerial parts of plants grown in the different treatments were air dried, extracted with acetone and tested against F. oxysporum. Plants exposed to 235 ppm K showed a marked increase in leaf number, plant height and fresh weight. Overall there was no significant difference (P > 0.05) among the treatments with respect to tissue nutrient content; K ranged from 3.56 ± 0.198 to 4.67 ± 0.29 %. The acetone extraction yield increased with increasing K fertilization: 58.75 ppm (16.67 ± 2.35 mg), 117.5 ppm (22.5 ± 4.79 mg), 235 ppm (210 ± 38.5 mg) but dropped to 40 ± 4.08 mg at 470 ppm K. Results from the anti-F. oxysporum bioassay showed that 58.75 and 235 ppm K treatments produced the most bioactive acetone extracts; MIC values of 0.49 and 0.645 mg/l, respectively. Acetone extracts obtained from plants exposed to 235 ppm K yielded the highest total activity, comparatively (P < 0.05). In conclusion, the optimum nutrient K level for growing H. cymosum hydroponically was 235 ppm. Chapter 3 focused on another important macro nutrient N and the objective was to determine the optimum nutrient requirements for growing the medicinal plant, Helichrysum cymosum (L.) (Asteraceae), hydroponically. Experiments were conducted to assess the effects of varied nitrogen (N) concentrations supplied as nitrate and ammonium on growth, tissue nutrient content, antimicrobial and total activities of acetone extracts of aerial parts. Treatments were based on a modified Hoagland’s nutrient formula. Six week old rooted cuttings were treated with 52.5 ppm, 105 ppm, 210 ppm and 420 ppm of N. Leaf number and stem height (cm) were recorded at weekly intervals and leaf analysis conducted. The effects of N treatments on plant growth parameters varied significantly among treatments; 52.5 ppm of N yielded the tallest plants (height) [19.4 ± 0.7 cm], while 105 ppm N yielded the maximum leaf number (68.1 ± 6.2) as well as maximum fresh weight of aerial parts was obtained with 105 ppm (15.12 ± 1.68 g). Nitrogen content of plant tissue ranged between 0.53 ± 0.03 and 4.74 ± 0.29% (d, f, 3, 12; f=14; P ≤ 0.002) depending on treatments. Powdered aerial parts (5 g) of H. cymosum obtained from the different N treatments were extracted with 100 ml of acetone. N treatment significantly affected the yield of crude extracts, which ranged from 87.5 ± 15.5 (52.5 ppm) to 230 ± 23.5 mg (105 ppm). Acetone extracts of plants that were exposed to varied N treatments were screened for anti-Fusarium oxysporum activity using minimum inhibitory concentration (MIC) method. The MIC value (0.073 ± 0.014 mg/ml) obtained with acetone extracts of plants exposed to 52.5 ppm N was significantly lower compared to the MICs of the other N treatments (105 [0.47 ± 0 and 0.705 ± 0.135 mg/ml], 210 [0.234 and 0.47 mg/ml] and 420 ppm [0.29 ± 0.101 mg/ml]) at 24 and 48 hours respectively. However, the total activities of extracts obtained among the four N treatments, which ranged from 0.062 ± 0.02 to 0.26 ± 0.06 ml/g was not statistically different at 24 or 48 hours (P > 0.05). LC-MS analysis of acetone extracts of H. cymosum plants obtained from the four treatments hinted that known anti-microbial agents such as apigenin, quercetin, kaempferol, helihumulone and quinic acids were present in the extracts and the quantity of helihumulone increased with increased nutrient N level. These results suggest that H. cymosum may be cultivated hydroponically and that the antimicrobial activity and/or the phytochemical profile of the crude acetone extracts is affected by nutrient nitrogen levels. Hydroponic cultivation of plants may be able to alleviate to an extent the pressure on wild medicinal plants.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016. / In Africa, herbal medicines are often used as primary treatments for a variety of ailments and diseases including HIV/AIDS and for HIV-related problems. In general, traditional medicines are not well researched scientifically in controlled studies, and are poorly regulated. Since the pharmacological effectiveness of natural products is affected by several native and foreign factors, studies on the variations of chemical composition and biological activity of these medicines are necessary. The processes of investigating plants to identify chemical substances are of great interest to natural product researchers because there is a need to discover new drugs for treating old and new diseases. These facts underscore an urgent need to develop new anti HIV and AIDS drugs with fewer or no side effects. Research into drug discovery and development using natural products is increasingly becoming better established. Marine organisms as a source of natural products delivered numerous novel compounds with multiple pharmacological properties. Natural products give endless opportunities for discovering novel compounds that can be used as drugs or backbones of drug leads. Manayi is a natural product that has been used to treat and manage people with HIV, but no scientific studies have been done to prove its efficacy on the HIV under controlled conditions. For the purposes of this study, cooked and uncooked Manayi product was evaluated for its efficacy on HIV in vitro. Manayi samples were collected in East London, Eastern Cape and sequentially extracted with hexane, chloroform, dichloromethane, butanol, methanol, and water as a series of increasingly polar solvents for its bioactive chemical constituents.

Thesis (M.Sc. (Horticulture)) --University of Limpopo, 2012 / Refer to document / the National Research Foundation

Thesis (Ph.D (Plant Physiology) --University of Limpopo, 2006 / Refer to document / National Research Foundation and ARC (Nelspruit)

Thesis (M.Sc. (Microbiology)) --University of Limpopo, 2015 / Five plant species: Ziziphus mucronata, Senna italica, Lantana camara, Ricinus communis and Lippia javanica, were selected for this study based on their use in traditional medicine. In preliminary screening, crude extracts were prepared using hexane, dichloromethane (dcm), acetone and methanol. Phytochemical profiles on Thin Layer Chromatography plates of the extracts were obtained by developing the plates in mobile phases of varying polarity. Tests for compounds such as tannins, flavonoids, alkaloids, phlobatannins, terpenes, steroids, cardiac glycosides and saponins were carried out. Antibacterial activity of the extracts was carried out using microdilution assay for Minimum Inhibitory Concentration and bioautography against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Enterococcus faecalis. Antioxidant activity of the extracts was performed using the 2, 2, diphenyl-1-picrylhydrazyl (DPPH) assay. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay and Phagoburst test were used to investigate the toxic effects and anti-inflammatory activity of the extracts on mouse Raw 264.7 macrophage cells, respectively. The presence of phytochemicals was observed on the chromatograms after the plates were sprayed with vanillin sulphuric acid reagent. The dcm extracts of the plants showed antibacterial activity against the selected bacterial species on the bioautograms. Senna italica and Z. mucronata showed the most activity bands on the bioautograms. Lippia javanica had the lowest MIC average of 0.56 mg/ml. Antioxidant activity was observed in the extracts of L. javanica and R. communis. The extracts promoted proliferation of the mouse macrophage cells Raw 264.7 at concentrations ranging from 0.31 mg/ml and 0.08 mg/ml. Senna italica leaves were selected for isolation of antibacterial compounds. The isolated compound was analysed on 1H and 13C nuclear magnetic resonance (NMR) and Mass Spectrometry (MS) for structural analysis. The structure could not be elucidated due to impurities in the compound but the tentative structure is a branched chain alkane with at least one ether linkage per repeating unit. Therefore the study shows that there are plant components with biological activities against wound infecting bacteria and a single lead compound was identified. / the National Research Foundation

Submitted in fulfillment of the requirements for the Degree of Master of Technology: Biotechnology, Durban University of Technology, 2009. / Dichrostachys cinerea, Carpobrotus dimidiatus, Capparis tomentosa and Leonotis leonurus are all plants that are indigenous to South Africa. These plants are used in traditional medicine to treat various ailments. However, there is little or no scientific data to justify these traditional uses. Furthermore, it is difficult to reconcile traditional knowledge with scientific evidence because of the overwhelming targeting of signal-responsive systems by plant defensive compounds, multiple sites of action and the connectedness of the signaling pathways, which provide many cures and have pleiotropic effects. In order to evaluate the action spectrum of these plants, and validate its widespread use, this research evaluated the antibacterial, antioxidant, anti-inflammatory, anti-mosquito and immunomodulatory properties of these plants. Antimicrobial activity of the extract was determined by evaluating the bactericidal and fungicidal action using the agar disc diffusion assay. Anti-oxidative properties of the extracts were tested using the DPPH photometric assay. Anti-inflammatory properties were carried out using the 5-lipoxygenase assay. The larvicidal, repellency and insecticidal assay was determined against A.arabiensis. The safe use of these plant extracts was determined by evaluating toxicity, a brine shrimp lethality assay and an in vitro cell culture system using human myelogenous leukemia cell line. Potential carcinogenic activity was evaluated using the Ames Salmonella Mutagenecity assay. The immunomodulatory activity of the extracts on human peripheral blood mononuclear cells 6 was evaluated on freshly harvested lymphocytes using the MTT assay. Cytokine response was evaluated by measuring the secretion of interferon-gamma and interleukin-10. Elucidation of the B cells, T cells, activated T cells, CD 4+, CD 8+ and NK cells was performed by flow cytometry. The extracts showed anti-microbial activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella oxytoca, Salmonella typhimurium, Serratia marcescens, Bacillus cereus and Tricoderm sp. The highest activity was shown by methanolic and aqueous extracts of L. leonurus leaves followed by methanolic and aqueous extracts of D. cinerea. Extracts of C. tomentosa and D.cinerea demonstrated a higher degree of free radical scavenging than rutin, which was used as a standard indicating that these plants have strong antioxidant properties. None of the plants showed significant anti-inflammatory activity when compared to NDGA. In the anti-mosquito assays, the extracts showed strong repellency and insecticidal activity. L. leonurus extracts demonstrated the highest insecticidal and repellency activity against the mosquito, and was also found to cause ‗knockdown‘ and mortality. The extracts display no toxicity, cytotoxicity and mutagenicity. The immunological studies for immune modulation showed that the methanol extracts of these plants induce a Th1- predominant immune response because they significantly suppressed the secretion of IL-10 and augment IFN-γ production, which are hallmarks used to indicate a stimulation of the innate immune response. This study also provides new information, with respect to the potential use of these plants in producing a mosquito repellent and an immunostimulant.

This work is an account of the investigations into the chemistry of two Cedrelopsis species from the Ptaeroxylaceae, Cedrelopsis grevei and Cedrelopsis microfoliata and a species from the Mesembryanthemaceae, Khadia alticola, as well as investigations into the synthesis of hydroxylated and prenylated chalcones. Cedrelopsis grevei, commonly called Katrafay, is amongst the many medicinal plants of Madagascar, being used to relieve muscle fatigue when the bark is soaked in hot water. Previous investigations of the wood and stem bark of this plant, have yielded chromones and coumarins and a recent investigation of the stem bark of a specimen collected in the north of Madagascar has yielded two novel limonoids of unusual structure, cedmilinol and cedmiline. The fruit and seed of Cedrelopsis grevei have not been studied previously and a phytochemical investigation of these plant parts was undertaken in this work. The dichloromethane extract of the fruit and seeds yielded, after column chromatography, a dihydrochalcone, uvangoletin, a flavanone, 5,7dimethoxypinocembrin, two simple chalcones, cardamonin and flavokawin Band three prenylated chalcones, 2’-methoxyhelikrausichalcone, cedreprenone and cedrediprenone. Three of these compounds, 2’-methoxyhelikrausichalcone, cedreprenone and cedrediprenone have not been isolated previously. Cedrelopsis microfoliata is another medicinal plant used in Madagascar. The leaves of this plant are used to prepare a decoction for woman to drink after childbirth. This is the first phytochemical investigation of Cedrelopsis microfoliata. The hexane extract of the dried stem bark yielded three compounds after column chromatography, a chalcone, microfolian and two flavanones, microfolione and (+)-agrandol. The dicholoromethane extract of this compound yielded four compounds after column chromatography, three coumarins, cedrecoumarin A, obliquin and microfolicoumarin and a sesquiterpenoid, sesquichamaenol. Four of the compounds isolated from Cedrelopsis microfoliata, microfolidione, microfolione, (+)-agrandol and microfolicoumarin have not been isolated previously. Khadia alticola is one of the species added to "Khadi", a Tswana/South Sotho name for beer brewed traditionally using the fleshy roots of a variety of taxa. Khadia is also reported to be used medicinally by the Manyika people of the Umtali district of Zimbabwe. The phytochemical investigation of the roots of Khadia alticola, which have not been studied previously, was undertaken to determine whether mesembrine type alkaloids were present in this species and thus contributing to the "potency" of the beer brewed traditionally. No mesembrine alkaloids were isolated in this work, however, a common sterol, sitosterol was isolated from the acidic chloroform fraction of the roots of this species and a flavonoid, 3,4',5,7-tetrahydroxyflavan was isolated from the basic chloroform fraction. Two chalcones, 3’,5’-dihydroxychalcone and 2’-hydroxychalcone were synthesised using the Claisen condensation. An isoprenylated acetophenone intermediate and an isoprenylated chalcone were also synthesised. / Thesis (Ph.D.)-University of Natal, Durban, 2001.