Optimization of extraction process of total flavonoids from Baijiu distillers' grains by response surface methodology and its antioxidant activity

Total flavonoids from Baijiu distillers' grains were extracted by ultrasonic-assisted ethanol technology. On the basis of single factor experiments, using ultrasonic temperature, ultrasonic power, liquid-solid ratio and ethanol volume fraction as the influence factors, the total flavonoids yield as evaluation index, the extraction process conditions of total flavonoids from distillers' grains were optimized by Box-Behnken experiments, and the antioxidant activity of total flavonoids from distillers' grains was evaluated in vitro. The results showed that the optimal extraction process of total flavonoids from Baijiu distillers' grains were obtained as follows: ultrasonic temperature 65 ℃, power 320 W, liquid and material ratio 40∶1 (ml∶g), ethanol volume fraction 66%. Under these optimal conditions, the total flavonoids yield from Baijiu distillers' grains reached 14.58 mg/g, and the radicals scavenging rates of DPPH and ABTS were 94.03% and 99.30%, respectively, which was close to the scavenging rates of vitamin C (VC) at the same mass concentration.