Screening Ontario Grown Onion Varieties for Antioxidant Properties

Agricultural products are in great demand in nutra-pharmaceutical and biomedical industries due to their potential health benefits to humans. Among all vegetables, onions are the most widely and largely consumed vegetable. Onions are rich in phenolic such as flavonoids, and anthocyanins. Flavonoid has the potential to be antioxidant, antibacterial, anti-inflammatory and anticancerous. Studies indicate that the decline in cardiovascular diseases, breast cancer, diabetes, inflammation and osteoporosis could be linked to the consumption of flavonoid based foods. In this study, we screen Ontario grown onion varieties namely Stanley, Safrane, Fortress, Lasalle and Ruby Ring for their antioxidant properties, and isolate the flavonoids present in them and the best Ontario grown onion variety was chosen for developing functional food traits. Extraction with solvents, low polarity water and supercritical carbon dioxide produced flavonoids such as kampferol, quercetin, myricetin, isorhamnetin from all the 5 onion varieties. High Performance Liquid Chromatography analysis of the extracted flavonoids showed the presence of sulfur containing compounds. The antioxidant efficacy of these extracts evaluated by oxygen radical scavenging assays, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays provided a better understanding of the nutrient profile of the Ontario grown onion varieties. Identification, enhancement and development of market quality traits such as antioxidants properties of Ontario-grown onions enhances their marketability as nutraceutical products, as natural antibiofilm coating agent for improved shelf life of packaged food and as a preservative in processed food.

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