Antioxidant activity of polyphenols from Ontario grown onion varieties using pressurized low polarity water technology

Natural by-products, especially flavonoids, are in great demand in the nutra-pharmaceutical and biomedical industries. In this study, Ontario-grown onion varieties, namely Stanley, Safrane, Fortress, Lasalle and Ruby Ring, were screened for their antioxidant properties. Pressurized low polarity water technology, an environmentally friendly technique, was employed to extract the flavonoids from the onion varieties, followed by quantification and analysis using High Performance Liquid Chromatography. The antioxidant activities in the extracted samples were determined using various antioxidant assays, such as 2,2-diphenyl-1-picrylhydrazyl, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid), ferric reducing ability of plasma, lipid peroxidation, total antioxidant capacity and oxygen radical absorbance capacity assays. The total phenolic content extracted from the Ruby Ring variety was the highest when compared to all the other yellow onion varieties tested. Our results indicate that Ruby Ring may be chosen as a preferred variety over other onion varieties to develop functional and health food products.