1. State Key Laboratory of Functions and Applications of Medicinal Plants, Guizhou Medical University, 3491 Gaohai Road, Guiyang 550014, P. R. China
2. The Key Laboratory of Chemistry for Natural Products of Guizhou Province and Chinese Academy of Sciences, 3491 Baijin Road, Guiyang 550014, P. R. China
3. School of Pharmacy, Guizhou University of Traditional Chinese Medicine, Guiyang 550025, P. R. China