1. Hunan Province Engineering Research Center of Bioactive Substance Discovery of TCM; Hunan University of Chinese Medicine; Changsha 410208 P. R. China
2. College of Pharmaceutical Sciences and Chinese Medicine; Southwest University; Chongqing 400715 P. R. China
3. National Center for Natural Products Research; University of Mississippi; University MS 38677 USA
4. Key Laboratory of Neurodegenerative Diseases of Ministry of Education; Capital Medical University; Beijing 100053 P. R. China