1. Department of Chemistry, Faculty of Science, University of Dschang, Dschang, Cameroon;
2. Department of Chemistry, Higher Teacher Training College, University of Yaounde I, Yaounde, Cameroon;
3. Organic and Bioorganic Chemistry, Faculty of Chemistry, Bielefeld University, Bielefeld, Germany;
4. Department of Chemical Engineering, School of Chemical Engineering and Mineral Industries, University of Ngaoundere, Ngaoundere, Cameroon