Extracts of 22 species of Meliaceae were examined for antimalarial activity using in vitro tests with two clones of Plasmodium falciparum, one sensitive to chloroquine (W2) and one chloroquine-resistant (D6). Twelve extracts were found to have activity, including extracts of Cedrela odorata wood and Azadirachta indica leaves, which contained the limonoid gedunin. These extracts were more effective against the W2 clone than the D6 clone, suggesting there is no cross-resistance to chloroquine. Gedunin was extracted in quantity, and nine derivatives prepared for a structure-activity study, which revealed essential functionalities for activity. The study also included four other limonoids derived from related Meliaceae. Only gedunin had better activity than chloroquine against the W2 clone. This active principle could be used to standardize a popular crude drug based on traditional use of A. indica in West Africa.

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A bioassay-guided isolation of antifungal compounds from an African land race of ginger, Zingiber officinale Roscoe, led to the identification of [6], [8] and [10]-gingerols and [6]-gingerdiol as the main antifungal principles. The compounds were active against 13 human pathogens at concentrations of <1 mg/mL. The gingerol content of the African land race was at least 3 x higher than that of typical commercial cultivars of ginger. Therefore, ginger extracts standardized on the basis of the identified compounds, could be considered as antifungal agents for practical therapy.

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The effects of three compounds, digitolutein (1), rubiadin 1-methyl ether (2) and damnacanthal (3) extracted from the stem bark and the roots of Morinda lucida Benth. on the growth of Plasmodium falciparum in vitro were investigated. The number of parasites (schizonts) decreased significantly in a dose-dependent manner, and 100% of inhibition was obtained with 30 to 40 micrograms of each compound tested. The IC50 values were calculated.