Extraction and antioxidant activity of polyphenols from green kumquat peel

Taking green kumquat peel as raw material, used ethanol as extraction solvent extracting polyphenols, determined the content of polyphenols by Folin-Ciocalteu method, identified the effect of ethanol concentration, temperature, solid-liquid ratio and time on the extraction efficiency of polyphenols. Based on single factor test, an orthogonal design was applied to optimize extraction process. Antioxidant activities of extract were evaluated by three different methods, such as DPPH and ABTS radical scavenging assay, potassium ferricyanide reduction method. The results showed that the optimum polyphenols extraction conditions as follows:extraction solvent60% ethanol (v/v) , extraction temperature 55℃, solid-liquid ratio (g/m L) 1∶30, extraction time 3h and one time.Under these conditions, the extraction rate of polyphenols was 3.68% (calculated on dry basis, w/w) . And the experiments of antioxidant activity showed that the extracted polyphenols presented the strong antioxidant activity to the DPPH and ABTS radical, and the IC50 was 1.38mg/m L and 0.49mg/m L, respectively. Potassium ferricyanide reduction test also showed similar results.