AIM:To investigate the relationship between theinhibited growth (cytotoxic activity) of berberine andapoptotic pathway with its molecular mechanism ofaction.METHODS:The in vitro cytotoxic techniques werecomplemented by cell cycle analysis and determinationof sub-G_1 for apoptosis in human gastric carcinomaSNU-5 cells.Percentage of viable cells,cell cycle,andsub-G_1 group (apoptosis) were examined and determinedby the flow cytometric methods.The associated proteinsfor cell cycle arrest and apoptosis were examined byWestern blotting.RESULTS:For SNU-5 cell line,the IC (50) was found tobe 48 μmol/L of berberine.In SNU-5 cells treated with25-200 μmol/L berberine,G_2/M cell cycle arrest wasobserved which was associated with a marked incrementof the expression of p53,Wee1 and CDk1 proteins anddecreased cyclin B.A concentration-dependent decreaseof cells in G_0/G_1 phase and an increase in G_2/M phasewere detected.In addition,apoptosis detected as sub-Gocell population in cell cycle measurement was proved in25-200 μmol/L berberine-treated cells by monitoring theapoptotic pathway.Apoptosis was identified by sub-G_0cell population,and upregulation of Bax,downregulation of Bcl-2,release of Ca(2+),decreased the mitochondrialmembrane potential and then led to the release ofmitochondrial cytochrome C into the cytoplasm andcaused the activation of caspase-3,and finally led to theoccurrence of apoptosis.CONCLUSION:Berberine induces p53 expression andleads to the decrease of the mitochondrial membranepotential,Cytochrome C release and activation ofcaspase-3 for the induction of apoptosis. AIM: To investigate the relationship between the inhibition of growth (cytotoxic activity) of berberine and apoptotic pathway with its molecular mechanism of action. METHODS: The in vitro cytotoxic techniques were complicated by cell cycle analysis and determination of sub-G_1 for apoptosis in human gastric carcinoma SNU-5 cells. Percentage of viable cells, cell cycle, and sub-G_1 group (apoptosis) were examined and determined by the flow cytometric methods. The associated proteins for cell cycle arrest and apoptosis were examined by Western blotting .RESULTS: For SNU-5 cell line, the IC (50 ) was found to be 48 μmol / L of berberine. In SNU-5 cells treated with 25-200 μmol / L berberine, G_2 / M cell cycle arrest wasobserved which was associated with a marked increment of the expression of p53, Wee1 and CDk1 proteins and decreased cyclin BA concentration-dependent decrease of cells in G_0 / G_1 phase and an increase in G_2 / M phasewere detected. In addition, apoptosis detected as sub-Gocell population in cell cycle measurem ent was proved in 25-200 μmol / L berberine-treated cells by monitoring theapoptotic pathway. Apoptosis was identified by sub-G_0cell population, and upregulation of Bax, downregulation of Bcl-2, release of Ca (2 +), decreased the mitochondrialmembrane potential and then led to the release of mitochondrial cytochrome C into the cytoplasm and caused the activation of caspase-3, and finally led to the activity of apoptosis. CONCLUSION: Berberine induces p53 expression and receptors to the decrease of the mitochondrial membrane potential, Cytochrome C release and activation of caspase- 3 for the induction of apoptosis.