Antioxidant activity of enzyme-assisted extract derived from round kumquat peel (Fortunella japonica)

Abstract

This study intends to apply enzyme-assisted extraction method to determine the antioxidant activity of round kumquat peel extract. Firstly, chemical composition of the kumquat peel was determined. Then, single factor test was employed to evaluate the effects of enzyme treatment conditions (enzyme amount and extraction time, ethanol concentration, mate-rial:ethanol ratio, extraction time and extraction temperature) on total phenolic content (TPC) and antioxidant activity of the kumquat peel ex-tract. The result showed that the content of phenolic compounds in the kumquat peel achieved 1.3%. The peel extract exhibited the maximum TPC of 335.96±16.79 milligrams of gallic acid equivalents (mg GAE)/g dry matter, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) cation radical (ABTS●+ ) scavenging activity of 1993.26±99.66 μmol Trolox Equivalent (TE)/g dry matter and ferric reducing antioxidant power (FRAP) value of 3202.86±160.14 μmol TE/g dry matter. This extract was obtained under enzyme treatment condition including enzyme content of 9 U/g dry matter, enzyme-treating time of 90 min and the extraction condition comprising of kumquat peel: 96% ethanol ratio of 1:40 (w/v), extraction time of 150 min and temperature of 50°C. The results revealed that the kumquat peel extract could be used as a potential natural antiox-idant in food and/or pharmaceutical products.