1. Department of Chemistry of Medicinal Natural Products, West China College of Pharmacy, Sichuan University, No. 17, Duan 3, Renmin Nan Road, Chengdu 610041, P.R. China
2. Medical Experiment and Test Center, Capital Medical University, Beijing 100069, P.R. China
3. College of Pharmaceutical Sciences, Capital Medical University, Beijing 100069, P.R. China