1. State Key Laboratories of Natural and Biomimetic Drugs and School of Pharmaceutical Sciences Peking University Health Science Center Beijing 100191 P. R. China
2. SATCM Key Laboratory of Compound Drug Detoxification Peking University Beijing 100191 P. R. China
3. Department of Chemistry and Cell and Molecular Biology Program College of Natural Science Colorado State University Fort Collins CO 80523‐1872 USA