1. Department of Chemistry, Faculty of Science , Université des Sciences et Techniques de Masuku , Box. 943 , Franceville , Gabon
2. Department of Animal Biology, Faculty of Sciences , University of Dschang , Box. 67 , Dschang , Cameroon
3. Department of Chemistry, Faculty of Science , University of Bamenda , Box. 39 , Bambili , Cameroon
4. Department of Organic Chemistry, Faculty of Science , University of Yaoundé 1 , Box. 812 , Yaoundé , Cameroon
5. International Center for Chemical and Biological Sciences, H.E.J. Research Institute of Chemistry , University of Karachi , Karachi-75270 , Pakistan
6. Department of Chemistry, Faculty of Science , Université des Sciences et Techniques de Masuku , Box. 943 , Franceville , Gabon , Tel.: +241 06043682/07622381, Fax: +241 01677578