Background: Breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer deaths among Canadian women. Cancer management through changes in lifestyle, such as increased intake of foods rich in dietary flavonoids, have been shown to decrease the risk associated with breast, liver, colorectal, and upper-digestive cancers in epidemiologic studies. Onions are high in flavonoid content and one of the most common vegetables. Additionally, onions are used in most Canadian cuisines.Methods: We investigated the effect of five prominent Ontario grown onion (Stanley, Ruby Ring, LaSalle, Fortress, and Safrane) extracts on two subtypes of breast cancer cell lines: a triple negative breast cancer line MDA-MB-231 and an ER+ breast cancer line MCF-7.Results: These onion extracts elicited strong anti-proliferative, anti-migratory, and cytotoxic activities on both the cancer cell lines. Flavonoids present in these onion extracts induced apoptosis, cell cycle arrest in the G2/M phase, and a reduction in mitochondrial membrane potential at dose-dependent concentrations. Onion extracts were more effective against MDA-MB-231 compared to the MCF-7 cell line. Conclusion: In this study, we investigated the extracts synthesized from Ontario-grown onion varieties in inducing anti-migratory, cytostatic, and cytotoxic activities in two sub-types of human breast cancer cell lines. Anti-tumor activity of these extracts depends upon the varietal and can be formulated into nutraceuticals and functional foods for the wellbeing of cancer patients. Overall, the results suggest that onion extracts are a good source of flavonoids with anti-cancerous properties.Keywords: onion extracts; flavonoids; anti-proliferative; breast cancer; cytotoxic activity
