1. Key Laboratory of Marine Drugs, Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, P. R. China
2. National Center for Drug Screening, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, P. R. China
3. Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education of China, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, P. R. China