Antioxidant-guided isolation and mass spectrometric identification of the major polyphenols in barley (Hordeum vulgare) grain

In the present study, the relative contribution of individual/classes of polyphenols in barley, to its antioxidant properties, was evaluated. Flash chromatography was used to fractionate the total polyphenol extract of Irish barley cultivar 'Irina', and fractions with highest antioxidant properties were identified using total phenolic content and three in vitro antioxidant assays: DPPH, FRAP, and ORAC. Flavanols (catechin, procyanidin B, prodelphinidin B, procyanidin C) and a novel substituted flavanol (catechin dihexoside, C27H33O16−, m/z 613.17), were identified as constituents of the fraction with highest antioxidant capacity. Upon identification of phenolics in the other active fractions, the order of most potent contributors to observed antioxidant capacity of barley extract were, flavanols > flavonols (quercetin) > hydroxycinnamic acids (ferulic, caffeic, coumaric acids). The most abundant polyphenol in the overall extract was ferulic acid (277.7 μg/g dw barley), followed by procyanidin B (73.7 μg/g dw barley).