Abstract: On the basis of one-factor-at-a-time experiments, response surface analysis was employed to optimize four process parameters affecting the ultrasonic-assisted extraction of total flavonoids from Avicennia marina leaves including ethanol concentration, solid-to-solvent ratio, ultrasonic power and extraction time. Besides, the antioxidant activity in vitro of total flavonoids from Avicennia marina leaves was evaluated. The optimal extraction conditions were found as follows: dried Avicennia mMarina leaf powder (particle size: 40－60 mesh) was extracted with 64.39% aqueous ethanol solution at a solid-to-solvent ratio of 1:28.20 (g/mL) and a ultrasonic power of 293.63 W for 40.00 min. Under these conditions, the extraction yield of total flavonoids was 4.185%. The IC50 of the obtained extract against hydroxyl, superoxide anion and DPPH radicals were 0.232, 0.829 mg/L and 23.692 mg/L, respectively. All three types of radicals could be more effectively scavenged by the extract than VC.

Key words: Avicennia marina leaves, flavonoids, ultrasonic-assisted extraction, response surface methodology (RSM), antioxidant activity