Abstract: The central composite design (CCD) method was employed to study the cellulase-assisted extraction process of total flavonoids from onion peel, and their antioxidant activities were also evaluated. The results showed that the optimum extraction conditions were obtained as follows: cellulose added at a ratio of 0.52% to hydrolyze onion peel suspended in a 40-fold volume of water adjusted to pH 5.0 for 105 min. The extraction rate of flavonoids under these extraction conditions was 2.32%. Moreover, antioxidation experiments showed that flavoniods from onion peel had very strong scavenging effects on DPPH free and hydroxyl radicasl, and the corresponding IC50 values were 3.751μg/mL and 4.267μg/mL. Meanwhile, onion peel flavonoid showed stronger reducing power when compared to tea polyphenols. These findings suggest that onion peel flavonoids are a group of strong antioxidants and have promising application prospects in healthcare foods and drugs.

Key words: onion peel, total flavonoids, cellulase, extraction, antioxidant activity