1. State Key Laboratory of Natural and Biomimetic Drugs Peking University Beijing 100191 P. R. China
2. Artemisinin Research Center Institute of Chinese Materia Medica China Academy of Chinese Medical Sciences Beijing 100700 P. R. China
3. Zhejiang Institute for Food and Drug Control Hangzhou 310004 P. R. China
4. School of Pharmacy Hebei Medical University Shijiazhuang 050017 P. R. China