1. Hunan Provincial Key Laboratory of Cytochemistry, Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation, School of Chemistry and Chemical Engineering, Changsha University of Science and Technology, Changsha 410114, P.R. China
2. Laboratory of Chemical Biology & Traditional Chinese Medicine Research, Ministry of Education, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, P.R. China
3. State Key Laboratory of Natural Medicines, Key Laboratory of Drug Quality Control and Pharmacovigilance, Department of Pharmaceutical Analysis, China Pharmaceutical University, Nanjing 210009, P.R. China
4. Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada