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Antiprotozoal activity of sesquiterpenes from Warburgia ugandensis towards Trypanosoma brucei rhodesiense and Plasmodium falciparum in vitro
The East African pepper-bark tree, Warburgia ugandensis Sprague (Canellaceae), has been widely used for the treatment of several diseases including malaria [1,2]. In the current study extracts and twelve sesquiterpenes obtained from W. ugandensis  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 IC50 values of 8.10 and 1.10µg/ml against the K1 strain of the malaria parasite and the 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 showed the highest antitrypanosomal activity with IC50 values ranging from 0.14–1.97µg/ml. Among the compounds tested against P. falciparum, muzigadiolide (1) and 11α-hydroxymuzigadiolide (2) were almost equally active against the 3D7 strain (IC50=1.79 and 1.69µg/ml, resp.), however only 2 was active against the K1 strain (IC50=1.82µg/ml).
Acknowledgements: We thank Mr. Melaku Wendafrash, The National Herbarium, Biology Department, Addis Ababa University, for plant identification. Financial support from ÖAD is appreciated.
References: 1. Kokwaro J. O. (1976) In: Medicinal plants of East Africa. East African Literature Bureau, Nairobi. 2. Watt J.M., Breyer-Brandwijk M.G. (1962) Medicinal and poisonous plants of Southern and Eastern Africa. E. and S. Livingstone, London. 3. Wube A.A., et al. (2005) Phytochemistry 66: 2309–2315.