1. Department of Biology and Biotechnology Research Institute, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China, State Key Laboratory for New Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 294 Taiyuan Road, Shanghai 200031, China, Department of Chemistry, Shanghai Second Medical University, 280 South Chongqing Road, Shanghai 200025, China, and Jiangsu Research Institute of Traditional Chinese Medicine, Maigaoqiao, Nanjing 210028, China