1. Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan, Department of Dental Pharmacology, Meikai University School of Dentistry, Sakado, Saitama 350-0283, Japan, and Laboratory of Phytochemistry, Kunming Institute of Botany, Academia Sinica, Kunming 650204, Yunnan, the People's Republic of China