1. Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan 251, Department of Life Science, Fu Jen Catholic University, Taipei, Taiwan 242, Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Department of Botany, National Museum of Natural Science, Taichung, Taiwan 404, Institute of Biochemistry, Academia Sinica, Taipei, Taiwan 115, and Graduate Institute of Pharmacognosy Science, Taipei Medical University, Taipei, Taiwan 110, Republic of China