In vitro activities of Strychnos alkaloids and extracts against Plasmodiumfalciparum

The in vitro antimalarial activities of 46 alkaloids and extracts from Stry chnos species were evaluated. Two types of quasidimeric alkaloids exhibit h igh and selective activities against Plasmodium. Strychnopentamine and isos trychnopentamine were active against chloroquine-sensitive and -resistant s trains (50% inhibitory concentration [IC50] approximate to 0.15 mu M), whil e dihydrousamharensine exhibited a 30-fold higher activity against the chlo roquine-resistant strain (IC50 = 0.03 mu M) than it did against the chloroq uine-sensitive strain.