1. Department of Organic Chemistry , Faculty of Science, University of Yaoundé I , P.O. Box 812 , Yaoundé , Cameroon
2. Department of Chemistry , Rhodes University , P.O. Box 94 , Grahamstown/Makhanda 6140 , South Africa
3. Department of Chemistry , Faculty of Science, University of Dschang , P.O. Box 67 , Dschang , Cameroon
4. Department of Chemistry , Higher Teachers’ Training College, University of Maroua , P.O. Box 55 , Maroua , Cameroon
5. Department of Chemistry , Faculty of Science, The University of Bamenda , P.O. Box 39 , Bambili , Cameroon
6. Department of Chemistry , Bielefeld University , P.O. Box 100131, 33501 Bielefeld , Germany
7. Department of Chemistry , Higher Teacher Training College, University of Yaoundé I , P.O. Box 47 , Yaoundé , Cameroon