Inhibition of P. falciparum by steroids isolated from Solanum nudum

Resistance to antimalarials has been widely reported and constitutes a major problem around the world. In Colombia, resistance of P. falciparum to chloroquine has been reported as 47%-97%, to amodiaquine 3%-7% and to sulfadoxine-pyrimethamine as 9%-13%. The search for new antimalarials is a priority and with this aim we studied the in vitro antimalarial activity of plants used by traditional healers. Incorporation of (3)H-hypoxanthine by the strain FCB-2 of P. falciparum was used to measure the degree of inhibition produced by the steroids SN-1 tumacone A (C(29)H(44)O(5)), SN-2 tumacone B (C(27)H(42)O(4)), SN-3 tumacoside A (C(35)H(54)O(10)), and SN-4 tumacoside B (C(33)H(52)O(9)). All compounds were obtained from the dried stems and leaves of Solanum nudum. The mean growth inhibition of P. falciparum was 71%, 56%, 21% and 12% with each of the compounds SN-1, SN-2, SN-3 and SN-4. These results constitute an important discovery since they may account for the antimalarial properties of extracts of Solanum nudum by a sensitive method. Future work should include study of the in vivo anti-malarial effect of these extracts.