Abstract:

The ultrasonic-assisted extraction of flavonoids from Changeshu grown black (duck blood) rice was
optimized by single-factor experiments and orthogonal experiment design to obtain maximum flavonoid yield.
The extracted flavnoids were investigated for their antioxidant activities by DPPH radical scavenging, hydroxyl
radical scavenging and superoxide anion radical scavenging assays. The results showed that the optimum
extraction conditions for solid-to-solvent ratio, ethanol concentration, ultrasonic power, temperature and
time were 1:60 (g/mL), 60%, 288 W, 50 ℃ and 40 min, respectively. The maximum yield of flavonoids under
these conditions was 1.415%. The flavonoids obtained exhibited powerful antioxidant activity in a concentrationdependent
manner, which, however, was inferior to that of VC. Therefore, this study concludes that Changshu black
rice is a good source of natural antioxidants.

Key words: Changshu black rice, flavonoids, ultrasonic-assisted extraction, antioxidant