1. Department of Chemistry, University of Buea, P.O Box 63, Buea, Southwest Province, Cameroon, Swiss Tropical Institute, Socinstrasse 57, CH-4002, Basel, Switzerland, Department of Chemistry, University of Glasgow, G12 8QQ, Scotland, U.K., Department of Chemistry, University of Minnesota, 207 Pleasant Street, SE, Minneapolis, Minnesota 55455, and Medicinal Foods & Plants (MEFOPLA), Bamenda, Northwest Province, Cameroon