1. Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China. Fax: +86 27 87543632; Tel: +86 27 87543032
2. Henan Engineering Research Center for the Exploitation of Chinese Medicine Resources in Dabie Mountain Area, Xinyang Agriculture and Forestry University, Xinyang 464000, People's Republic of China