Barley and malt polyphenols and their antioxidant properties

Ten different barley cultivars and their corresponding malts were analysed for monomeric and oligomeric flavan-3-ols content by using high-performance liquid chromatography ultraviolet detection-electrospray ion trap mass spectrometry. The Folin-Ciocalteau and the vanillin spectrophotometric assays were used for the assessment of the total polyphenol and total flavan-3-ol content respectively, and the antioxidant activity was determined by DPPH and FRP. Catechin and prodelphinidin B3 were respectively the major monomeric and dimeric flavan-3-ols. Moreover, prodelphinidin B3 was shown to be the main contributor for the radical scavenging activity both for barley and malt. The same samples were used to obtain different fractions. The contribution of bound phenolics to the total polyphenol content was significantly higher than that of free and esterified fractions. Catechin and ferulic acid, quantified by HPLC-DAD, were the most abundant phenolics in the free and bound fractions, respectively. The antioxidant activities of phenolic fractions were investigated using the radical scavenging assay (DPPH) and the ferricyanide reducing power (FRP). Further the hot water extracts of barley cultivars and corresponding malts were analyzed. The ferric reducing antioxidant power (FRAP) and radical scavenging activity (ABTS) and indicator time test (ITT) were compared. The total polyphenol content, as measured according to Folin-Ciocalteu's method, was positively correlated with all antioxidant methods used. Free phenolic compounds were measured by HPLC with CoulArray detector. The dominant phenolic compound was ferulic acid.