Antiprotozoal activity of drimane and coloratane sesquiterpenes towards Trypanosoma brucei rhodesiense and Plasmodium falciparum in vitro

The extracts and 12 sesquiterpenes obtained from the East African medicinal plant Warburgia ugandensis Sprague (Canellaceae) were assessed for their antiplasmodial activity against the chloroquine-sensitive (3D7) and chloroquine-resistant (K1) strains of Plasmodium falciparum and antitrypanosomal activity against Trypanosoma brucei rhodesiense. The dichloromethane extract displayed strong antiplasmodial and antitrypanosomal activities with IC 50 values of 8.10 and 1.10 ?g/mL against K1 strain of the malaria parasite and STlB900 strain of T. b. rhodesiense, respectively. Among the compounds evaluated for inhibition of trypomastigotes, both drimane and coloratane sesquiterpenes possessing aldehyde groups at positions 8 and 9 were found to show most antitrypanosomal activity with IC50 values in the range 0.56-6.4 ?M. The antiplasmodial assays also revealed that the six coloratane and six drimane sesquiterpenes isolated from this extract exhibited significant antitrypanosomal activity with IC50 values ranged from 0.45 to ?114 ?M. Among the compounds tested against the malarial parasite P. falciparum 11?-hydroxymuzigadiolide (3) was most active with an IC50 value of 6.40 ?M.