1. School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, Jiangsu Province, P. R. China
2. CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
3. School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210046, Jiangsu Province, P. R. China
4. Jiangsu Institute for Food and Drug Control, Nanjing 210019, Jiangsu Province, P. R. China
5. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore