1. Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College (Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education), Bejing 100050, People's Republic of China, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, People's Republic of China, and Department of Chemistry, Beijing Normal University, Beijing 100875, People's Republic of China