Fractionation and quantification of phenolic antioxidants from Saeunamu (Ostrya japonica)

Abstract

Saeunamu (Ostrya japonica), a natural plant in Jeju, was extracted and fractionated on a Sephadex LH-20 column, and their phenolic compounds and integral antioxidative capacity (IAC) were evaluated. Eight fractions were obtained, and the relative contents of ethanol fractions (F1-F6) and methanol fractions (F7, F8) were 64.0 and 33.1%, respectively. Total phenolics in the methanol fractions were high as 672.8 and 613.3 mg catechin equivalents (CE)/g in F8 and F7, compared with those in the ethanol fractions as 438.4 and 411.1 mg CE/g in F4 and F5, respectively. Only 4 phenolics such as protocatechuic acid, caffeic acid, catechin, and quercetin were identified. Catechin was concentrated as 4.6 and 4.4 times in F7 and F8, and quercetin was 2.9 and 2.6 times in F5 and F6, respectively, compared with the unfractionated. IAC of water-soluble substances were high as 6.41 and 7.71 mmol ascorbic acid equivalents/g, and those of lipid-soluble substances were high as 2.50 and 2.41 mmol Trolox equivalents/g in F4 and F5, respectively. It was concluded that ethanol fractions (F4-F6) possessing strong IAC may be used as a natural source of antioxidants in functional food ingredients.