Abstract:Hawthorn flavonoids were extracted by superfine pulverization assisted ultrasound，and their antioxidant activity in vitro was studied.The particle size of super-finely pulverized hawthorn powder was used as the independent variable，and the scavenging rates of DPPH，hydroxyl and ABTS+free radicals were adopted to evaluate the antioxidant activity of hawthorn flavonoids.Scanning electron microscope was employed to observe the microstructure changes of the super-finely pulverized hawthorn powder.The results showed that when the particle size of super-finely pulverized hawthorn powder was 1.0 mm，the extraction rate of hawthorn flavonoids reached the maximum（13.01%），and the antioxidant activity reached the highest，among which the DPPH free radical scavenging rate was 95.2%，and the hydroxyl radical scavenging rate was 46.4%，ABTS+free radical scavenging rate was 99.6%.The hawthorn flavonoids obtained by the superfine pulverization assisted ultrasound was found with enhanced antioxidant activity due to the change of surface morphology and the increase of specific surface area under the scanning electron microscopy.