1. Ta-Jen Pharmaceutical Junior College, Ping Tung Hsien 907, Taiwan, Republic of China
2. Graduate Institute of Natural Products, Kaohsiung Medical College, Kaohsiung 807, Taiwan, Republic of China
3. Pharmacological Institute, College of Medicine, National Taiwan University, Taipei 100, Taiwan, Republic of China
4. Department of Chemistry, National Cheng Kung University, Tainan 700, Taiwan, Republic of China