1. Institute of Pharmaceutical Biology and Biotechnology; Heinrich Heine University; Universitätstrasse 1, Geb. 26.23 40225 Düsseldorf Germany
2. Faculty of Science; Department of Chemistry; University of Douala; P. O. Box 24157 Douala Cameroon
3. Department of Pharmacognosy; Faculty of Pharmacy; Mansoura University; 35516 Mansoura Egypt
4. Department of Organic Chemistry; University of Debrecen; P. O. Box 400 4002 Debrecen Hungary
5. State Key Laboratory of Natural and Biomimetic Drugs; Peking University; 100191 Beijing China
6. Department of Pharmacognosy; Faculty of Pharmacy; King Saud University; Riyadh Saudi Arabia