Objective To study on the mechanism of killing and apoptosis inducing effect of total alkaloid in the CSA(Capparis spinosa L.alkaloid,CSA)on human hepatocarcinoma cell Line HepG-2.Methods The killing effect of the CSA on human hepatocarcinoma cell Line HepG-2 was measured by MTT method.Morphological observation of the HepG-2 cells was completed by fluorescence microscope.The apoptosis inducing effect and changing of mitochondria membrane potential of the CSA on the HepG-2 cells were measured by flow cytometry.In addition,effect of intracellular Ca2+ level of the CSA on the HepG-2 cells was studied by laser confocal microscope.Results The CSA has obvious cytotoxicity on the HepG-2 and seems to be dose-dependent,and its IC50 value is 162.4 μg·mL-1.The HepG-2 cells have characteristic morphologic changes of apoptosis by the function of CSA,and the apoptosis percentage is higher than the natural one.The progress of cells cycle from S phase to G2 phase has been blocked,and the mitochondria membrane potential is markedly decreased,and the intracellular Ca2+ level is increased by the function of CSA.Conclusions The CSA has obviously killing and apoptosis inducing effect on human hepatocarcinoma cell Line HepG-2 by the mechanism of decreasing the mitochondria membrane potential and increasing the intracellular Ca2+ level. Objective To study on the mechanism of killing and apoptosis inducing effect of total alkaloids in the CSA (Capparis spinosa L. alkaloid, CSA) on human hepatocarcinoma cell line HepG-2. Methods The killing effect of the CSA on human hepatocarcinoma cell Line HepG- 2 was measured by MTT method. Morphological observation of the HepG-2 cells was completed by fluorescence microscope. The apoptosis inducing effect and changing of mitochondria membrane potential of the CSA on the HepG-2 cells were measured by flow cytometry. In addition, effect of the intracellular Ca2 + level of the CSA on the HepG-2 cells was studied by laser confocal microscope. Results The CSA has obvious cytotoxicity on the HepG-2 and seems to be dose-dependent, and its IC50 value is 162.4 μg · mL-1 The HepG-2 cells have characteristic morphologic changes of apoptosis by the function of CSA, and the apoptosis percentage is higher than the natural one. The progress of cells cycle from S phase to G2 phase has been blocked, and the mitochondri a membrane potential is markedly decreased, and the intracellular Ca2 + level is increased by the function of CSA.Conclusions The CSA has obviously killing and apoptosis inducing effect on human hepatocarcinoma cell line HepG-2 by the mechanism of decreasing the mitochondria membrane potential and increasing the intracellular Ca2 + level.