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

Abstract

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.