1. Department of Chemistry; Graduate School of Science and Technology; Kumamoto University; 2-39-1, Kurokami, Chuo-ku Kumamoto 860-8555 Japan
2. Division of Material Science and Engineering; Graduate School of Science and Engineering; Yamaguchi University; 2-16-1 Tokiwadai Ube 755-8611 Japan
3. Department of Natural Medicines; Graduate School of Pharmaceutical Sciences; Kumamoto University; Oe-honmachi 5-1, Chuo-ku Kumamoto 862-0973 Japan