1. School of Pharmaceutical Sciences, Tsinghua University, Haidian Dist, Beijing 100084, P. R. China
2. Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, 2A Nanwei Rd, Xicheng Dist, Beijing 100050, P. R. China
3. College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan 250014, P. R. China
4. Key laboratory of Molecular Pharmacology and Drug Evaluation (Yantai University), Ministry of Education; Collaborative Innovation Center of Advanced Drug Delivery System and Biotech Drugs in Universities of Shandong, Yantai University, Yantai 264005, P. R. China