Antiplasmodial activity of Uvaria klaineana.

Crude extracts of Uvaria klaineana Engler and Diels (Annonaceae) stems showed in vitro activity against chloroquine-resistant K1 strain of Plasmodium falciparum. The most active extract was the basic dichloromethane extract containing crude alkaloids (IC50 = 3.55 microg/mL). The bioassay-guided fractionation of this extract led to the isolation of the major alkaloid crotsparine (1) which showed an antiplasmodial activity against the chloroquine-sensitive Thai strain of P. falciparum and the chloroquine-resistant K1 and FcB1 strains of P. falciparum. Two minor alkaloids were also identified as crotonosine (2) and zenkerine (3). Their structures were elucidated using 2D-NMR techniques.