Antioxidant activity of barley tea and their composition

In our previous paper, we assessed the antioxidant effect of warm water extract from barley grain on the oxidative deterioration of oil. In the present, antioxidant compositions in hot water extract from barley grain (referred to as barley tea hereafter) were identified, and their antioxidant activity was measured. Polyphenols in barley tea were identified by using high performance liquid chromatography (column, Develosil ODS-HG, mobile phase, distilled water-acetonitrile-0.05 M phosphoric acid 90 : 10 : 0.05 v/v), thin-layer chromatography (the fraction by silicagel G 60) and ultra violet spectrum analysis. Antioxidant activity was assessed by the Rancimat method so as to determine the rancid point (induction time) and the oven test. Polyphenols in barley tea was detected, and the structures of polyphenols were established as catechol, garlic and gentisic acids, gallocatechin (GC) and epigallocatechin gallate (EGCG). The main component of polyphenols was catechol. On the other hand, very small quantities of the GC and EGCG existed in barley tea. Barley tea and ethyl acetate extract obtained from barley tea showed preventive effects on oxidative deterioration of oil. Especially, ethyl acetate extract were markedly higher than that barley tea. Antioxidant activity of gentisic and gallic acids showed a greater preventive effect