Bioaccessibility of flavonoids and total phenolic content in onions and its relationship with antioxidant activity.

Antioxidant activity, total phenolic content, and flavonoids in onion were determined using the DPPH method, the Folin-Ciocalteu method, and high-performance liquid chromatography analysis, respectively. Myricetin was the most bioaccessible among flavonoids in both red and yellow onions after digestion. The result suggest that the antioxidant activity of yellow and red onions was stronger in the outer layer than in the inner layer and strong correlation was found between antioxidant activity and total phenolic content (r(2) = 0.927).