1. Chongqing Key Laboratory of Natural Product Synthesis and Drug Research Chemical Biology Research Center School of Pharmaceutical Sciences Chongqing University Chongqing 401331 P. R. China
2. Jiangsu Key Laboratory for Functional Substances of Chinese Medicine School of Pharmacy Nanjing University of Chinese Medicine Nanjing Jiangsu 210023 P. R. China
3. State Key Laboratory of Bioactive Substance and Function of Natural Medicines Institute of Materia Medica Chinese Academy of Medical Sciences and Peking Union Medical College Beijing 100050, P. R. China