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Purpose: To evaluate the effects of ebracteolatain A (EA) and ebracteolatain B (EB) from Euphorbia ebracteolata Hyata (Euphorbiaceae) on the proliferation of HepG2 cells and the possible mechanisms.
Methods: EA and EB from E. ebracteolata were obtained by column chromatography. 3-(4,5- Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry assays were used to study the cytotoxic and pro-apoptotic activities of EA and EB against HepG2 cells. Western blot assay was used to investigate the possible mechanisms of action.
Results: EA and EB were successfully isolated from E. ebracteolata by column chromatography. The results of MTT assay indicate that EA and EB have significant anti-proliferative activities against HepG2 cells in dose- and time-dependent manners with half maximal inhibitory concentration (IC50) of 28.48 and 31.72 μg/mL. respectively. The results of flow cytometry assay suggest that EA and EB significantly (p < 0.01) induced the apoptosis of HepG2 cells at the levels of 47.45 and 42.26 %, respectively. Western blot data indicate that EA and EB significantly (p < 0.05 or 0.01) down-regulated the expression levels of anti-apoptotic proteins (survivin and Bcl-2) and up-regulated the expression levels of proapoptotic proteins (Smac, Bax, c-caspase-3 and c-caspase-9) in mitochondria-mediated apoptotic pathway.
Conclusion: EA and EB inhibit the proliferation of HepG2 cells, the probable mechanisms being associated with mitochondria-mediated apoptosis.
Keywords: Euphorbia ebracteolata, Phloroglucinol derivatives, Mitochondria-mediated apoptosis, Flow cytometry, Western blot