1. Department of Chemistry, University of Dhaka, Dhaka 1000, Bangladesh
2. Department of Pharmacognosy, Graduate School of Pharmaceutical science, Kyoto University, Yoshida, Sakyo-Ku, Kyoto 606-8501, Japan
3. Faculty of Pharmaceutical sciences, Kanazawa University, 13-1 Takara-Machi, Kanazawa 920, Japan
4. Department of Chemistry, Kent State University, USA