1. School of Pharmaceutical Sciences, South-Central University for Nationalities, Wuhan 430074, P. R. China
2. State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, P. R. China
3. College of Pharmacy, Henan University of Chinese Medicine, Zhengzhou 450008, P. R. China