| Nile tilapia,Oreochromis niloticus,is one of the popular species grown in freshwater aquaculture.Nile tilapia skin contains a high level of protein,which can be used as good resources for hydrolysate or bioactive peptides preparation.Developing the reasonable application of Nile tilapia could has great economic value and theoretical significance.In this study,gelatin was extracted from Nile tilapia skin and then respectively hydrolysed by alcalase(A),neutral proteinase(N),flavourzyme(F),papain(P),and trypsin(T)for 60 min or 120 min.Antioxidant efficacy of respective hydrolysates were evaluated using scavenging activities of 2,2;-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid)(ABTS)radical,1,1-diphenyl-2-picrylhydrazyl(DPPH)radical,hydroxyl radical and lipid peroxidation in linoleic acid.The results showed that the Tilapia Skin Gelatin peptide had obvious antioxidant activity,which less than that of glutathione(GSH).Papain hydrolysates for 60 and 120 min of hydrolysis(P-60 and P-120)and alkaline protease hydrolysates for 60 min of hydrolysis(A-60)had the highest ABTS radical scavenging activity,the IC50 values were 44.45±0.89,46.24±1.35 and 51.82±1.49mg/mL.P-60,P-120 and A-60 showed strong DPPH scavenging activity,the IC50 values were 16±0.75,20.57±0.37 and 32.71±0.02mg/mL.A-60,P-60 and A-120 exhibited potent hydroxyl radical scavenging activity,the IC50 values were 11.24±0.22,12.17± 1.43 and 16.81 ±0.30mg/mL.The more potent inhibitory activity of linoleic acid peroxidation were A-60,T-120 and F-60,of which IC50 values were found to be 7.46±0.91,12.73±0.85 and 13.36±0.97mg/mL,respectively.After comprehensive evaluation,the antioxidant activities of hydrolysates for 60min of hydrolysis were higher than that of 120min hydrolysates.The results suggest that Tilapia Skin Gelatin peptide could serve as a potential source of functional food ingredients for antioxidant activities.Secondly,we established the model of gastrointestinal tract digestion in vitro,combined with the molecular weight distribution,and then determined the changes of antioxidant acti-vities of Tilapia Skin Gelatin peptide which were hydrolyzed for 60 min before and after digestion in vitro gastrointestinal digestion.The results showed that after in vitro gastrointestinal digestion,the hydroxyl radical scavenging activity of F-60,P-60 and N-60 were significantly increased by 1.28,1.97 and 4.22-fold,respectively.The free radical scavenging activity of ABTS was significantly decreased after digestion,except for P-60,which increased by 0.26-fold.Linoleic acid lipid peroxidation inhibition activity was significantly reduced(except P-60,which increased by 1.15-fold).Furthermore,DPPH radical scavenging activity was also significantly reduced(except for T-60,which increased by 1-fold,and no change in T-60).After comprehensive evaluation,the antioxidant activities of A-60 and P-60 were higher than other samples.The content of 1-3kDa of F-60,A-60 and N-60 were increased by 1.62,0.52 and 3.59-fold,respectively.But the content of T-60 and P-60 had no specific change before and after gastrointestinal digestion in vitro.The molecular weight distribution of all the hydrolysates were mainly concentrated in 3-5kDa before and after digestion in vitro.It suggested that the hydrolysates were still mixture.The changes of antioxidant activities may be related to the increase of 1-3kDa and 3-5kDa components in the system.Finally,in this study,we investigated the protective effect of Tilapia Skin Gelatin(A-60 and P-60)on H2O2-induced oxidative stress in human hepatoma cell(HepG2)oxidative stress model.The results showed that 100 ?M H2O2 for 1 hour could induced the oxidative stress in HepG2 cells.It was found that both P-60and A-60(250-500 ?g/mL)could increased the cell viability and protective effect on H2O2-induced oxidative damage.in HepG2 cells. |
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