1. Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, PO Box 2457, Riyadh 11451, Saudi Arabia
2. Faculty of Pharmaceutical Sciences, Setsunan University, Nagao-toge-machi, Hirakata, 573-01, Japan
3. Core Research for Evolutional Sciences and Technology, Japan Science and Technology, Tokyo 113-0033, Japan
4. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China