Chromatographic separation and tandem MS identification of active peptides in potato protein hydrolysate that inhibit autoxidation of soybean oil-in-water emulsions

A previously developed antioxidative potato protein hydrolysate was fractionated using gel filtration. The efficacy of different fractions for inhibiting lipid oxidation in soybean oil-in-water emulsions, neutralizing 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS ^+·) radicals, and chelating prooxidative metal ions was investigated. Low-molecular-weight fraction Peak 3 (709 Da) exhibited the strongest antioxidant activity and radical scavenging activity. Active peptides based on the ABTS^+· scavenging assay were isolated by RP-HPLC and purified by UPLC. The amino acid sequence determination by MS/MS identified eight prominent peptides in the antioxidative Peak 3 fraction, of which Thr-Tyr, Tyr-Phe-Glu, Tyr-Ser-Thr-Ala, and Asn-Tyr-Lys-Gln-Met matched the sequence of papatin.