Antioxidant Properties And Synergistic Effect Of Small Peptides

The antioxidant activity of protein hydrolysate is among one of the hottest topic in foodand medicine research field. Although there are seas of studies on production, separation,purifying, defining the sequence and application of antioxidant peptides in various foodsystems. Until now the knowledge of protein hydrolysate, especially the mechanism ofantioxidation and the relation between function and construction are still not enough to beguidance for putting peptides into use. This paper studied the pure small peptides with similarconstruction, trying to understand the antioxidant activities in various systems of peptides orpair of peptides. Additionally the interactions of small peptides with nonpeptidic antioxidantswere investigated. It has actual meaning to raise the realistic value and attaching value ofpeptides.Firstly, the thesis took the eight pure peptides as samples, including GSH, YHY(Tyr–His–Tyr), GY (Gly–L–Tyr), L–carnosine, PHH (Pro–His–His), GG (Gly–Gly),N–carnosine (N–Acetyl–carnosine) and AQ (L–Ala–Gln), to investigate their antioxidantactivities in different assays. It has been found that GSH has the strongest DPPH scavengingactivity among the eight peptides, slightly bigger than BHA. In ABTS+scavenging assay, GY,YHY and GSH exerted the best activity; L–carnosine can chelate ferrous ion while otherpeptides did weakly. And GSH revealed high reducing power. In linoleic acid autoxidationsystem, the first five order of antioxidant activity was L-car>PHH>YHY=GY>GSH.Secondly, it leveraged the interactions of peptides in ABTS+scavenging system, FRAPand linoleic acid system, and discussed the possible mechanism of interactions in ABTS assay.It could be observed that the GY and PHH, GY and AQ, GSH and GG all promoted slightlysynergist effect in different ratios in ABTS system. And this positive effect was influenced bythe concentration of main antioxidant peptide. This phenomenon may possibly be producedboth by hydrogen bond and hydrophobic interaction. The tyrosine-contained peptides exertedsynergistic effect with other peptides in FRAP. However, peptides did not promote positiveinteraction in linoleic acid system.Finally, to evaluate the interaction between peptides and nonpeptidic antioxidants, thethesis also put pairs in ABTS+scavenging system, FRAP and linoleic acid system.Consequentially, positive interactions happened between VC, caffeic acid and most peptides,raising the ABTS+scavenging activity of pairs. The synergistic effect of PHH and catechinwas so high that the synergistic coefficient was more than300%. GY was observed to havepositive effect with VE, VC, BHA, EGCG, catechin, caffeic acid, rosmarinic acid, quercetin,and Na2SO3. When VC was added into two peptide mixture, synergistic effect still happened,but without the additive synergistic effect. PHH and GY‘s pair could also interact with all nine nonpeptidic antioxidants in positive way, among which the catechin promoted highest. InFRAP system, GSH had good interactions with rosmarinic acid, caffeic acid, quercetin,catechin and Na2SO3. And the peptides with little reducing ability also took synergistic effectwith nonpeptidic antioxidants. The positive effect also could be observed within GSH and VE,catechin, quercetin in linoleic acid autoxidation system.