1. Xiamen Key Laboratory of Marine Medicinal Natural Product Resources Xiamen Medical College Xiamen 361023 P. R. China
2. Engineering Research Center of Marine Biopharmaceutical Resource Fujian Province University Xiamen Medical College Xiamen 361023 P. R. China
3. National Center for Natural Products Research School of Pharmacy University of Mississippi University MS 38677 USA
4. Key Laboratory of Marine Drugs Chinese Ministry of Education School of Medicine and Pharmacy Ocean University of China Qingdao 266003 P. R. China