1. Department of Chemical Sciences , University of Johannesburg , Doornfontein Campus, P.O. BOX 17011 , Johannesburg , 2028 , South Africa
2. Department of Animal Biology and Physiology, Laboratory of Animal Physiology , University of Yaoundé I, Faculty of Sciences , P.O. Box , 812 Yaoundé , Yaoundé , Cameroon
3. Department of Organic Chemistry , University of Yaoundé I, Faculty of Sciences , P.O. Box , 812 Yaoundé , Yaoundé , Cameroon