Comparative Studies on a Standardized Subfraction of Red Onion Peel Ethanolic Extract (Plant Substance), Quercetin (Pure Compound), and Their Cell Mechanism and Metabolism on MDA-MB-231

This study indicates the presence of quercetin in subfraction F1 and the standardized value of F1 derived from research using ultra-performance liquid chromatography (UPLC) and AlCl(3) colorimetric assays, which further proved that both F1 and quercetin are potential growth inhibitors in MDA-MB-231 cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In the process, staining of F1-treated cells with annexin/propidium iodide (PI) reduced cell proliferation and induced only S and G2 phases of cell cycle arrest in the treated cells by flow cytometry. Quercetin reduced cell proliferation by inducing apoptosis and S phase arrest. The 5′-bromo-2′-deoxyuridine (BrdU) incorporation of DNA synthesis in MDA-MB-231 cells was also inhibited after F1 and quercetin treatments. F1 and quercetin induced CYP1A1 and CYP1B1 gene expression, but only F1 induced CYP2S1 gene expression in the treated cells. Both F1 and quercetin inhibited the proliferation of MDA-MB-231 cells in different ways, but F1 is likely a better potential anticancer agent derived from the green approach towards breast cancer treatment.