1. Faculty of Science, Department of Chemistry , University of Buea , P.O. Box 63 , Buea , Cameroon
2. Department of Pharmaceutical Chemistry , Martin-Luther University Halle-Wittenberg , Kurt-Mothes-Str. 3 , Halle (Saale) , 06120 Germany
3. Institute of Botany , Technische Universität Dresden , Zellescher Weg 20b , Dresden , 01217 Germany