Strychnogucines A and B, two new antiplasmodial bisindole alkaloids from Strychnos icaja

A reinvestigation of Strychnos icaja roots has resulted in the isolation of two tertiary quasi-symmetric bisindole alkaloids named strychnogucines A ( 1) and B (2). Their structures were identified by means of spectroscopic da ta interpretation. Compound 2 was highly active in vitro and compound 1 mod erately active against four strains of Plasmodium falciparum. Strychnogucin e B (2) was more active against a chloroquine-resistant strain than against a chloroquine-sensitive one (best CI50, 80 nM against the W2 strain). In a ddition, this compound showed a selective antiplasmodial activity with 25-1 80 times greater toxicity toward P. falciparum, relative to cultured human cancer cells (KB) or human fibroblasts (WI38).