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

•Pressurized low polarity water is an eco-friendly extraction technique.•Yellow onion variety had the highest total flavonoid content than the red varieties.•Red onion variety exhibited higher antioxidant activity than the yellow varieties.•Flavonoids from Ontario onions serve as a promising source of natural antioxidants.