1. Department of Organic Chemistry , Faculty of Science, University of Yaoundé I , P.O. Box 812 Yaoundé , Cameroon
2. Laboratory of Phytochemistry, Centre for Research on Medicinal Plants and Traditional Medicine, Institute of Medical Research and Medicinal Plants Studies , P.O. Box 13033 , Yaoundé , Cameroon
3. Department of Animal Biology and Physiology , Faculty of Science, University of Yaoundé I , P.O. Box 812 Yaoundé , Cameroon
4. Department of Chemistry , Higher Teacher Training College, University of Yaoundé I , P.O. Box 47 Yaoundé , Cameroon
5. Department of Organic and Bioorganic Chemistry , Faculty of Chemistry, Bielefeld University , P.O. Box 100131 , 33501 Bielefeld , Germany
6. Department of Inorganic and Structural Chemistry , Faculty of Chemistry, Bielefeld University , D-33501 Bielefeld , Germany
7. Department of Chemistry , Faculty of Science, The University of Bamenda , P.O. Box 39 , Bambili , Cameroon