1. Key Laboratory of Tropical Medicinal Resource Chemistry of Ministry of Education; Key Laboratory of Tropical Medicinal Plant Chemistry of Hainan Province, College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158, P.R. China
2. Key Laboratory of Tropical Translational Medicine of Ministry of Education; Hainan Provincial Key Laboratory for Research and Development of Tropical Herbs, College of Pharmacy, Hainan Medical University, Haikou 571199, P. R. China