Studies On The Chemical Constituents Of Rabdosia Weisiensis C.Y.Wu And Weisiensin B, A New Diterpenoid Induce Apoptosis Of Bel-7402

There is abundant natural resources of Rabdosia weisiensis C.Y.Wu distributed in the South of Gansu province. In China, it was used as traditional treatment of various diseases, such as gastric ulcer, enteritis et al. In order to study the pharmic mechanism deeply, and to search for the compounds which have novel structure and biological activity, the chemical components of Rabdosia weisiensis C.Y.Wu distributed in the South of Gansu province, was studied in this paper. Eleven compounds were obtained from the dried stems and leaves of the R.weisiensis C.Y.Wu. By Spectroscopic means (IR,MS,¹H-NMR,¹³C-NMRå’ŒDEPT), their structures were identified as ursolic acid (1), 3β-acetyl-ursolic acid (2), pedalitin (3), flavogadorinin (4), daucousterol (5), -stiosterol (6) Kamebacetal A (7), Kamebanin (8), weisiensin B (9), Macrocalyxin D (10) and ExcisaninK (11). Weisiensin B is a novel compound among them.The antitumor activity was determined in vitro by the SRB assay of five ent-kaurane type diterpenoids obtained from R..weisiensis C.Y.Wu. The result indicates that five compounds have significant cytotoxicity against Bel-7402 and HO-8910. The sequence of cytotoxicity against Bel-7402 is Kamebanin,Macrocalyxin D,Kamebacetal A,weisiensin B,Excisanin K and the sequence of cytotoxicity against HO-8910 is Macrocalyxin D,Kamebanin,Kamebacetal A,weisiensin B,Excisanin K. The 50% inhibition concentration (IC₅₀) of weisiensin B isl0±2.0uM and 32±7.0uM against human tumor Bel-7402 and HO-8910.The cell was treated with weisiensin B, and the number of survival cell is detected by means of cell-growth curve. Cell cycle and apoptosis rate were determined by flow cytometry. As a result, Weisiensin B can arrest cell cycle at G₂/M phase and induce apoptosis in Bel-7402 cells. Apoptosis morphological changes of Bel-7402 cells is compatible with the chromatin condensation and fragmentation under a fluorescence microscope. The typical DNA fragmentation was performed by using agarose gel electrophoresis, and we found genomic DNA fragment into integer multiples of 180-bp units.