1. Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan, Temko Corporation, 4-27-4 Honcho, Nakano-ku, Tokyo 164-0012, Japan, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand, and Division of Pharmacognosy, Phytochemistry and Narcotics, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan