Antioxidant activity and physicochemical properties of 1 ku fraction by ultrafiltration of bigeye tuna (Thunnus obesus) head protein hydrolysate

Abstract

To produce bioactive peptides from the by-products of fish processing,bigeye tuna(Thunnus obesus) head was hydrolyzed by alcalase,and the tuna head protein hydrolysate(THPH) was fractionated through ultrafiltration membranes with a range of molecular weight cutoffs(MWCO) of 8,5,3 and 1 ku,respectively,to yield the fraction THPH-1 with MW distribution1 ku.The antioxidant activities of THPH-1were evaluated using reducing power,free radical scavenging and aged model mice induced by D-galactose.The physicochemical properties of THPH-1 were analysed also.THPH-1 showed evident radical scavenging activity in a dose-dependent manner with the IC50 values for hydroxyl radical,superoxide radical and 1,1-diphenyl-2-pycrylhydrazyl(DPPH) radical being 1.38,0.73 and 0.93 mg/mL respectively.The reducing power of THPH-1 was 0.763 at 12.5 mg /mL.The activities of superoxide dismutase(SOD) of liver and the activities of glutathione peroxidase(GSH-PX) of liver and serum in aged model mice were significantly increased(P0.05) compared with that of the normal control group mice after 42 days administrated orally at a dose of 30 mg/kg THPH-1,and the content of malondialdehyde(MDA) of serum in aged model mice was significantly decreased(P0.01).The physicochemical properties showed that THPH-1contained 96.40% of protein(on dry basis),0.11% of fat and 4.86% of ash.The total hydrophobic amino acids content of THPH-1was 35.8% of the total amino acids content.The molecular weight distribution of the higher activity fractions of THPH-1were located at 1 802-2 519 u and 422-922 u.These results indicate that THPH-1from tuna head hydrolysate would be very fairly helpful in the preparation of antioxidative peptides and a beneficial ingredient for functional food.