Abstract: A microwave-assisted extraction, using ethyl alcohol as solvent was adopted for extracting flavonoids from orange peel. The effect on extraction rate of flavonoids of factors such as concentration of alcohol, extraction time and the ratio of solid to liquid were investigated. The results from the single factors and orthogonal tests showed that when the conditions were 75% alcohol (valume fraction), extraction time 7 min and the ratio of solid to liquid 1:30, the yield of flavonoids was up to 12.04%.The free redical scavenging effects of orange peel extraction was determined by DPPH method. Orange peel extracts obtained under various conditions showed definite scavenging effects on DPPH redical. A significant positive correlation was found between DPPH scavenging rate of extracts and flavonoids content.

Key words: orange peel, microwave-assisted extraction, natural antioxidant, free redical