1. Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan, Kobayashi Pharmaceutical Corporation, 30-3, 1-chome, Toyokawa, Ibaraki-shi, Osaka 567-0057, Japan, and School of Agriculture, Kyusyu Tokai University, 5435 Minamiaso, Aso, Kumamoto 869-1404, Japan