1. a Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education of China) , School of Chemistry & Chemical Engineering of Guangxi Normal University , Guilin 541004, P.R. China
2. b School of Chemistry and Chemical Engineering, Central South University , Changsha 410083, China
3. c Division of Pharmaceutics and Biopharmaceutics Faculty of Pharmaceutical Sciences , University of British Columbia , Vancouver, BC, V6 T 1Z3, Canada