1. Department of Chemistry, Higher Teachers’ Training College, University of Yaounde 1, P. O. Box 47, Yaounde, Cameroon
2. H. E. J. Research Institute of Chemistry, International Center for Chemical Sciences, University of Karachi, Karachi 75270, Pakistan
3. Département des Sciences Pharmaceutiques, Faculté de Médecine et Sciences Pharmaceutiques, Université de Douala, B. P. 2701, Douala, Cameroon
4. Department of Organic Chemistry, Faculty of Science, University of Yaounde 1, B. P. 812, Yaounde, Cameroon
5. Department of Chemistry, University of Stellenbosch, P/Bag X 1, Matieland, 7602, South Africa
6. Department of Chemistry, Laboratory of Structural Chemistry, University of Antananarivo, P. O. Box 906, 101-Antananarivo, Madagascar
7. Institute of Environmental Research (INFU) of the Faculty of Chemistry, Chair of Environmental Chemistry and Analytical Chemistry, Technical University Dortmund, Otto-Hahn-Str. 6, D-44221 Dortmund, Germany