1. School of Chemistry; Sun Yat-sen University; Guangzhou 510275 P. R. China
2. State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, Cancer Center; Sun Yat-sen University; Guangzhou 510060 P. R. China
3. School of Pharmaceutical Sciences; Sun Yat-sen University; Guangzhou 510006 P. R. China
4. Guangdong Technology Research Center for Advanced Chinese Medicine; Guangzhou 510006 P. R. China