Plants as sources of antimalarial drugs. Part 7. Activity of some species of meliaceae plants and their constituent limonoids

Crude extracts of three species of the Meliaceae family used traditionally as febrifuges (Azadirachta indica, Cedrela odorata, Guarea multiflora), together with 27 limonoids extracted from the meliaceous plants were evaluated for their in vitro antimalarial activity against chloroquine resistant K1 strain of Plasmodium falciparum. None of the extracts tested showed high antiplasmodial activity and only five compounds were found to be moderately active (IC50 values: 0.72–3.11 μ/mL). The most active limonoid, gedunin, of low in vitro cytotoxicity did not inhibit P. berghei in a 4 day test in mice (at the dose of 90 mg/kg/day, s.c. and i.p., no toxicity observed). Meliaceous plants may not exert their activity solely via direct action against malaria parasites, and the beneficial therapeutic effects claimed by patients might be due to the antiinnflammatory and immunomodulating activities recently described for these plants.