Antioxidant Activity Of Hydroxyproline Peptides

Most oral bioactive peptides are difficult to penetrate intestinal mucosa due to excessive molecular weight,are unstable in gastrointestinal tract,and are rapidly metabolized in systemic circulation.Hydroxyproline,as a characteristic component of collagen,can make collagen-derived oligopeptides highly resistant to peptidase and protease in peptide sequence.After oral administration of collagen hydrolysate,it is digested and absorbed by gastrointestinal tract.The sequence is Hyp-Gly(Hyp-G)?Ala-Hyp(A-Hyp)?Leu-Hyp(L-Hyp)?Ile-Hyp(I-Hyp)? Pro-Hyp(P-Hyp)?Ser-Hyp(S-Hyp)?Phe-Hyp(F-Hyp)?Glu-Hyp(E-Hyp)?Gly-Pro-Hyp(GP-Hyp)?Glu-Hyp-Gly(E-Hyp-G)?Ser-Hyp-Gly(S-Hyp-G)?Ala-Hyp-Gly(A-Hyp-G)?Pro-Hyp-Gly(P-Hyp-G)?Phe-Hyp-Gly(F-Hyp-G)?Leu-Hyp-Gly(L-Hyp-G)and other peptide forms exist in blood.Some studies have confirmed the antioxidant activity of collagen hydrolysate and collagen peptide,and have also studied the amino acid sequence and content of collagen-derived hydroxyproline small peptide in blood,but whether the hydroxyproline small peptide of the above sequence has antioxidant activity remains to be explored.This article takes Hyp-G?A-Hyp?L-Hyp?I-Hyp?P-Hyp?S-Hyp?F-Hyp?E-Hyp?GP-Hyp?E-Hyp-G?S-Hyp-G?A-Hyp-G?P-Hyp-G?F-Hyp-G?L-Hyp-G as research objects.The antioxidant activities of 15 hydroxyproline peptides and their antioxidant synergistic effects with non-peptide antioxidants(VC?VE and rutin)were determined by four antioxidant evaluation methods of DPPH radical,ABTS radical,superoxide anion radical and hydroxyl radical,and the interaction of 15 hydroxyproline peptides and antioxidants with human serum albumin was studied by molecular docking.The main results are as follows:In vitro antioxidant experiments,the DPPH radical scavenging activities of 15 hydroxyproline peptides were similar,the scavenging rate was only about 15%,and the scavenging ability was low.L-Hyp and I-Hyp showed better scavenging ability in ABTS radical scavenging ability,and the scavenging rate could reach about 60% at a certain concentration.S-Hyp?F-Hyp?P-Hyp?A-Hyp-G?S-Hyp-G?GP-Hyp have no ABTS radicalscavenging activity,while the other small peptides have low activity.The 15 small peptides showed higher scavenging ability of hydroxyl radical and superoxide anion radical.The hydroxyl radical scavenging activity and superoxide anion radical scavenging activity of 15 small peptides combined with non-peptide antioxidants showed obvious antagonism,and the scavenging small peptides on hydroxyl radical and superoxide radical were not suitable for synergistic use with non-peptide antioxidants.In DPPH radical and ABTS radical scavenging,the combination of VC,VE and tea polyphenols can improve the antioxidant capacity of small peptides and make up for the deficiency of 15 hydroxyproline small peptides in DPPH radical and ABTS radical scavenging.According to the numerical results of "-CDOCKER Energy",15 small hydroxyproline peptides can be combined with HSA sites I and II.Although the compactness is not strong,they can still form reversible complexes with increased molecular weight.Therefore,the combination of hydroxyproline small peptide and HSA has certain influence on the absorption and utilization of small peptide.There is a binding between antioxidant and HSA site I.Antioxidants,small peptides and HSA binding amino acid residues are consistent,mainly for hydrophobic interaction.Although the combined use of small peptides and antioxidants can increase the antioxidant activity of small peptides and there is binding competition with small peptides,the "-CDOCKER Energy" value of antioxidants at HSA site I is not high and competition is not strong,which has little effect on the bioavailability problem caused by the increase of small peptide molecular weight.