Abstract: In this study,microwave extraction technology integrated with ethanol and aqueous ammonium sulfate solution two-phase separation was applied to extract total flavonoids from Ramie skin.Based on single factor experiment,ethanol concentration,solid-liquid ratio,the concentration of ammonium sulfate,extraction power and the time of extraction on extraction yield of total flavonoids were investigated.By orthogonal experiment,the optimum extracting conditions were optimized as follows:ratio of solid to liquid was 1:50 g/mL,the concentration of ammonium sulfate was 0.2 g/mL,extraction power was 200 W,extraction time was 120 s,the ethanol concentration was 70%,the highest extraction yield reached to 2.442% under the optimized extraction conditions.In addition,the total flavonoids extract showed scavenging activities on O₂^-·and ·OH in the antioxidant activity assays.

Key words: Ramie skin, microwave, aqueous two-phase, total flavonoids, antioxidant activity