1. State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, Yunnan, P. R. China, Laboratory of Molecular Immunopharmacology, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan, P. R. China, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, P. R. China, and Graduate School of the Chinese Academy of Sciences, Beijing 10039, P. R. China