Schumanniophyton magnificum and Glypheae brevis are important medicinal plants growing wild in the West African rain forest. They are used in folkloric medicine in the treatment of epilepsy and convulsion as well as for some other diseases. The purpose of this work was to investigate the aspect of folkloric use in order to support folkloric claims and document the findings. The extracts were prepared from ground plant material by a continuous extraction method. Five hundred grams of ground plant material were continuously de-fatted with 2 L petroleum ether (60°- 80°) in a Soxhlet apparatus for about 5 h. The resulting marc was dried and the chemical constituents extracted hot in a Soxhlet apparatus for about 8 to 10 h with 2 L aqueous ethanol (70%). The efficacy of the extraction method was confirmed using standard bioassays and phytochemical analyses. The anti-convulsant activity of the crude extracts was evaluated in vivo against chemically induced convulsions using three different animal models, namely the strychnine, the picrotoxin and the pentylenetetrazole tests. The acute and delayed toxicity test results showed that in all the animal models investigated very high doses, about four times higher than the protective doses of the extracts, were required to kill 50% of the population of animal used. Phytochemical assays of the extracts indicated the presence of alkaloids only in S. magnificum root extract and glycosides in extracts from both species. The glycosides were positive to Baljet, Xanthydrol and Keller-Kiliani tests for cardiac glycosides. S. magnificum and G. brevis chemical constituents were initially isolated with a sequential fractionation method starting with a highly non-polar solvent and gradually increasing to a more polar solvent. The fractions were pooled on the basis of TLC similarity profiles when viewed under the UV light at 254 and 366 nm and were found to have two and four major UV absorbing fractions for S. magnificum and G. brevis respectively. Radio-receptor binding tests were used to assess the anti-convulsant activities of the hydro-alcoholic crude extracts, the organic and aqueous fractions of the crude extracts, partially purified components and pure components in in vitro tests against some standard GABA[A] receptor antagonists, muscimol and isoguvacine respectively. The anti-convulsant activities resided in the aqueous fractions of the hydro-alcoholic crude extracts of both plants. The purely organic fractions of G. brevis demonstrated no activity while all the fractions of the aqueous component demonstrated some degree of activity. The anti-convulsant activity of S. magnificum was found only in one fraction-Fraction 1. This Fraction was further investigated and one of the components appear to be responsible for the activity. The structure of the active constituent was 5,7dihdroxy-2 methylbenzopyran-4-one, a noreugenin. A second bioactive compound, schumanniofoside, was identified from Fraction M[5.2] from S. magnificum. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.

Petroleum ether, dichloromethane, and 80% ethanol extracts of 15 plant species collected in Nigeria were screened for in vitro antibacterial, anti-inflammatory and antimalarial activities. Antibacterial activity was tested using the agar diffusion method, while the minimum inhibitory concentrations (MIC) of the active extracts were determined using the microtitre serial dilution method. Most antibacterial activity detected was against Gram-positive bacteria with Staphylococcus aureus being the most susceptible. The highest activity was found in petroleum ether and dichloromethane leaf extracts of Mallotus oppositifolius; petroleum ether, dichloromethane and ethanolic root extracts of Newbouldia laevis; and ethanolic root extracts of Morinda lucida and Canthium subcordatum. Against the Gram-negative bacterium Escherichia coli, the highest activity was found in dichloromethane leaf extracts of Newbouldia laevis, ethanolic root extracts of Phyllanthus amarus, Mallotus oppositifolius, and Canthium subcordatum. A total of 60 plant extracts were screened for antiplasmodial activity. A chloroquine sensitive strain of Plasmodium falciparum (D10) was used. In the assay, the parasite lactate dehydrogenase (pLDH) activity was used to measure parasite viability. About 11 extracts showed promising activity with an IC₅₀ ranging from 2.5 to 13.4 µg/ml. The petroleum ether leaf extract of Hyptis suaveolens had the highest activity (IC₅₀ = 2.5 µg/ml). The cyclooxygenase (COX-1 and COX-2) assays were used to test for anti-inflammatory activity. All the plant species, with the exception of Hedranthera barteri and Picralima nitida showed anti-inflammatory activity. Apart for a few ethanolic extracts, all the activities were recorded with petroleum ether and dichloromethane extracts. Employing bioassay-guided activity fractionation, an antibacterial anthraquinone identified as emodin was isolated from ethanolic root extract of Senna occidentalis. Although this compound had been isolated from other sources, this was the first report of isolation from Senna occidentalis. Using a similar approach a novel antimalarial diterpenoid was isolated from the petroleum ether leaves extract of Hyptis suaveolens. It had IC₅₀ of 0.1 µg/ml. This new compound is worthy of further investigation and may act as an important lead compound for future antimalarial drugs. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2005.