Simultaneous treatment of xanthorrhizol and curcumin alters the mitochondrial transmembrane potential and induces apoptosis in MDA-MB-231 cells. MitoCapture™ dye was found localized and fluoresces red (arrow) in the mitochondrial of untreated cells. Number of cells fluoresces red was decreasing in line with the increasing dose of treatment, suggesting the disruption of the mitochondrial transmembrane potential (A). Phase contrast fluorescence images show that untreated cells were stained homogenously and no fluorescence was observed. In contrary, cell shrinkage was observed in the treated cells and fluorescence (arrow) was clearly detected in the nuclear region, indicating apoptotic morphology (B). X – xanthorrhizol. XC – combination of xanthorrhizol and curcumin. TAM – Tamoxifen (positive control).