1. CAS Key Laboratory of Chemistry of Northwestern Plant Resources, Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
2. University of Chinese Academy of Sciences, Beijing 100049, P. R. China
3. College of Chemistry & Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
4. Qingdao Center of Resource Chemistry & New Materials, Qingdao 266071, P. R. China