Fractionation and characterization of antioxidant peptides derived from barley glutelin by enzymatic hydrolysis.

The antioxidant properties of the barley glutelin hydrolysates were evaluated based on their radical scavenging capacity (DPPH/O₂(·-)/OH(·)), Fe(2+)-chelating effect and reducing power. Alcalase hydrolysates (AH) demonstrated significantly higher antioxidant capacity than those treated by flavourzyme in most of the assays. The AH was separated using ultra-filtration and reversed-phase chromatography, and assessment of the fractions indicated that the large-sized peptides (Mw>10 kDa) possessed stronger DPPH scavenging activity and reducing power, whereas small-sized peptides (Mw<1 kDa) were more effective in Fe(2+)-chelating and OH(·) scavenging effect. The hydrophobic fraction contributed more to Fe(2+)-chelating and OH(·) scavenging activity. Four peptides contributing to antioxidant activities were identified using LC-MS/MS: Gln-Lys-Pro-Phe-Pro-Gln-Gln-Pro-Pro-Phe, Pro-Gln-Ile-Pro-Glu-Gln-Phe, Leu-Arg-Thr-Leu-Pro-Met and Ser-Val-Asn-Val-Pro-Leu. Compared to the positive controls, AH exhibited excellent Fe(2+)-chelating activity and strong DPPH/OH scavenging effect. Thus hydrolyzed barley glutelin is a potential source of antioxidant peptides for food and nutraceutical applications.