Leaves Triterpenoids Induce Breast Cancer Cell Apoptosis via the Mitochondrial Pathway.

is a traditional Chinese medicine. The leaves of , specifically the dried leaves of the plant, are commonly consumed as tea in China. In this study, leaves triterpenoids (FLT) were isolated and purified from the dried leaves of , and their in vitro antitumor activity as well as associated molecular mechanisms were systematically investigated. First, the primary components of FLT were determined using high-performance liquid chromatography (HPLC), and the results revealed ursolic acid (70.67%), oleanolic acid (16.23%), and betulinic acid (4.59%) as the major components. Next, the results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that FLT exhibited strong antiproliferative activity ( < 0.05) toward human breast cancer MCF-7 and MDA-MB-231 cells. Moreover, the flow cytometry detection of apoptosis using Annexin V-fluorescein isothiocyanate/propidium iodide (Annexin V-FITC/PI) revealed that FLT significantly induced apoptosis in MCF-7 and MDA-MB-231 cells in a dose-dependent manner ( < 0.001). Laser confocal microscopy showed that FLT was mainly located in the mitochondria and lysosome of cells. Meanwhile, after the FLT (15 μg/mL) treatment of MCF-7 and MDA-MB-231 cells, the mitochondrial membrane potential (MMP) ( < 0.001) and intracellular reactive oxygen species (ROS) level ( < 0.001) were significantly reduced. Finally, western blotting demonstrated that FLT (10 and 15 μg/mL) significantly reduced B-cell lymphoma-2 (Bcl-2) ( < 0.001) and cysteinyl aspartate specific proteinase-3 (caspase-3) protein levels ( < 0.001), but significantly increased Bcl-2 homologous antagonist/killer (Bak) protein ( < 0.05 or  < 0.001), cleaved-caspase-3 protein ( < 0.001), dynamic-related protein 1 (DRP1), and mitochondrial fission 1 protein (FIS1) levels ( < 0.01 or  < 0.001). Taken together, the results indicated that FLT promoted the apoptosis of MCF-7 and MDA-MB-231 cells by activating the mitochondrial pathway. This effect may be attributed to FLT affecting the expression of the Bcl-2 family in mitochondria by promoting DRP1 and FIS1-mediated mitochondrial division, thereby activating the cleavage of caspase-3 and ultimately leading to cell apoptosis.