1. Department of Medicinal Natural Product Chemistry, School of Pharmaceutical Sciences, Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China
2. Department of Pathology, Institute of Cancer Research, Chengde Medical College, Chengde, Hebei 067000, P.R. China
3. Department of Central Laboratory, the Affiliated Hospital of Chengde Medical College, Chengde, Hebei 067000, P.R. China