Preliminary antimalarial and phytochemical studies of some Kenya medicinal plants
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Malaria, caused by Plasmodium species, inflicts over 270 million people and kills two million every year. Herbal medicine is practiced worldwide and has been recognized by WHO as an essential part of primary health care programmes. This thesis gives the results of antimalarial screening of nine Kenyan medicinal plants belonging to the families Conbretaceau, Euphorbiaceae, Melastomataceae, Papilionaceae and Moraceae. The antimalarial activity was quantitatively measured by the ability of the extracts to inhibit the uptake of radiolabelled nucleic acid precursor by Plasmodium falciparum during the short-term culture in microtitration plates. Using an ID50 of 50m/ml as a cut off dose, the results showed that out of 30 extracts, 57.1% were active against the chloroquine non-sensitive strain (ENT36) while 33.3% against the sensitive strain (K67). The phytochemical analysis of the stembark of Terminalia spinosa, stems of Dissotis brazzae and leaves of Suregada zanzibariensis and Phyllanthus rticulatus indicated the presence of alkaloids, flavonoids, steroids, triterpenoids, tannis, saponins and volatile oils among others. In the last two decades, work on antimalarials of plant origin other than alkaliods has intensified. This has led to the discovery of antimalarials from classes of compounds such as terpenoids (as sesquiterpene lactones and quassinoids), flavonoids and coumarins. Tannis have been found to be effective anticytotoxic agents. Chromatographic separations of the methanolic extract of the stembark of Terminalia spinosa led to the isolation of some pure compounds which have partially been identified as flavoids and terpenoids by ultraviolet and infra-red spectroscopy.