1. Artemisinin Research Center Guangzhou University of Chinese Medicine Guangzhou 510006 P. R. China
2. Lingnan Medical Research Center the first Affiliated Hospital of Guangzhou University of Chinese Medicine Guangzhou 510006 P. R. China
3. Division of Chemistry and Biological Chemistry School of Physical & Mathematical Sciences and School of Chemical & Biomedical Engineering Nanyang Technological University Nanyang 637371 Singapore
4. School of Pharmaceutical Sciences Guangzhou University of Chinese Medicine Guangzhou 510006 P. R. China