1. Contribution from the Faculty of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan, Chemical Analysis Center of Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan, and Research Center for the Natural Sciences, University of Santo Tomas, Espana, Manila 1008, Philippines