Antimalarial activity of traditionally used Western Ghats plants from India and their interactions with chloroquine against chloroquine-tolerant Plasmodium berghei.

An ethnopharmacological investigation was undertaken on Western Ghats plants traditionally used to treat malaria; 50 plants were very carefully selected from total of 372 plants, and 216 extracts were prepared and tested for in vivo antiplasmodial activity alone and in combination with chloroquine (CQ) against CQ-tolerant Plasmodium berghei (strain NK65). In in vivo antiplasmodial activity when plant extract alone is used, 81 extracts (or 37.5%) gave 52.90% significant parasitemia inhibition on day 4 postinfection and 39 extracts (or 18%) gave 41-89% mouse survival on day 9 postinfection. In combination with CQ on day 11 postinfection, 103 extracts (or 47.68%) gave mouse survival rate of 92% and on day 14 gave maximum mouse survival up to 70-79%. The fact that these activities were up to fourfold higher with CQ mostly resulted in longer mouse survival because of significant parasitemia inhibition. Our investigation have confirmed that above 70% of the plant extracts showed moderate to high in vivo antimalarial activity when used alone and in combination with CQ, and most of the extracts showed border line to good synergistic activity.