1. Faculty of Pharmaceutical Sciences, University of Tokushima, Shomachi 1-78, Tokushima, 770-8505, Japan, School of Dentistry, University of Tokushima, Kuramoto-cho, Tokushima 770-8504, Japan, BBI-Biotech Research Laboratories, Perry Parkway, Gaithersburg, Maryland 20877, and Natural Products Laboratory, School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599