1. Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan 807, Republic of China, Faculty of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan, and Faculty of Biomedical Laboratory Science, College of Health Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan 807, Republic of China