Cancer is the leading cause of mortality in Canada and other industrialized nations; the development of new/improved cancer therapies is desperately needed and continues to be a major focus of cancer research. Flavonoids, which are found in high levels in onions, have been shown to exert antiproliferative and potentially anti-cancer activities. To test their therapeutic potential, we assessed the antiproliferative, cytotoxic, apoptosis-inducing, and anti-migratory activities of five onion varieties grown in Ontario against human adenocarcinoma (Caco-2) cells. The properties of onion extracts were compared to pure extracts of flavonoids known to exhibit antiproliferative effects (quercetin, myricetin, and kaempferol). We compared more than one variety of onion, as agronomic and genetic factors influence the composition, as well as the quality of phytochemicals (e.g. flavonoids) in plant cultivars. We found that all onion varieties exhibited antiproliferative activity similar to purified flavonoids. The cytotoxic effects of the Stanley and Fortress onion varieties were strongest among the selected cultivars, as determined via lactate dehydrogenase (LDH) assays, while Safrane extracts showed the weakest activity. The Stanley and Lasalle cultivar extracts also had strong anti-migratory effects. Altogether these onion extracts may contain one or more compounds that may be effective anti-cancer therapies, while the Stanley extract showed the most comprehensive biological activities against Caco-2 cells.
Keywords: Anti-migratory; Apoptosis; Caco-2 cells; Onion extracts; Pressurized low polarity water.
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