| The study was granted by National 863 Program under Grant research and development on the stability and processing applicability of active protein of pine nut(Pinus koraiensis)(2013AA102206-5).The activity of antioxidant peptides was studied which mainly focused on the effects of pulsed electric field(PEF)technology on the activity of pine nut pentapeptides.In this paper,three antioxidant peptides Lys-Cys-His-Gln-Pro(KCHQP),Gln-Cys-His-Lys–Pro(QCHKP)and Gln-Cys-His-Gln–Pro(QCHQP)identified from pine nut protein were used as the research object.The FRAP value,DPPH free radical scavenging capacity and hydroxyl radical scavenging capacity were used as evaluation indicators to investigate the effects of PEF treatment on the antioxidant activity of pine nut antioxidant pentapeptides.In addition,the high performance liquid chromatography(HPLC)technology,fourier transform infrared spectroscopy(FT-IR)technology and circular dichroism(CD)technology were used to analyzing the structure changes of PEF-treated and untreated pine nut antioxidant pentapeptides.This study provided basis for revealing the mechanism of effects of PEF treatment on antioxidant activity of peptides.The results of this study were listed below:(1)The chemosynthetic pine nut peptides KCHQP,QCHKP and QCHQP were taken as experimental objects and the antioxidant activity of them were evaluated in vitro.The QCHQP was with the maximum FRAP value of 14.56±0.40 mmol Fe2+/mg,the KCHQP took second place of 8.94 mmol Fe2+/mg,while the QCHKP was with the minimum FRAP value of 7.69±0.20 mmol Fe2+/mg.The KCHQP was with the maximum DPPH free radical scavenging ability of 89.10±0.20%,QCHQP took second place of 74.36±0.16%,while the QCHKP was with the minimum DPPH free radical scavenging ability of 45.04±1.70%.The peptide with the maximum cellular antioxidative ability(CAA)was KCHQP with the CAA unit of 78.40±1.47,QCHQP took second place of 40.81±3.76,while the QCHKP possessed the minimum CAA unit of 22.51±2.12.In addition,all of the three peptides were nontoxic on Hep G2 cells and they could not induce the cell proliferation.(2)In the study of PEF treatment effects on antioxidant activity of pine nut peptides,four treatment conditions(15 k V/cm,1800 Hz;20 k V/cm,1800 Hz;15 k V/cm,2400 Hz;20 k V/cm,2400 Hz)were designed to clear-cut the effects of PEF on antioxidant activity of pine nut antioxidant pentapeptides by measuring the FRAP value and DPPH free radical scavenging ability,and the results were verified by hydroxyl radical scavenging experiment.The results showed that PEF treatment improved the FRAP value of KCHQP by 1.25 mmol Fe2+/mg,DPPH free radical scavenging ability improved by 4.14%,and the hydroxyl radical scavenging ability by 17.61%;PEF treatment improved the FRAP value of QCHKP by 5.15 mmol Fe2+/mg,DPPH free radical scavenging ability improved by 28.34%,and the hydroxyl radical scavenging ability by 12.95%;however,the antioxidant activity of QCHQP was inhibited which the FRAP value decreased by 3.12 mmol Fe2+/mg,DPPH free radical scavenging ability decreased by 10.71%,and hydroxyl radical scavenging ability decreased by 0.77%.(3)In the study of PEF treatment effects on structures of pine nut antioxidant pentapeptides,the PEF-treated and untreated KCHQP,QCHKP,and QCHQP were used as research objects.The basic structure of peptide chain,fuctional groups,and secondary structures of peptides were analyzed using HPLC,FT-IR and CD technology.The results showed that the basic structure of the peptide chain of KCHQP,QCHKP,and QCHQP were not changed,but the peptides’ amide band absorption peak intensity of FT-IR were strengthened.What’s more,the antioxidant pentapeptides can form secondary construct in aqueous solution,the content of α-helix of KCHQP and QCHKP were decreased,while the QCHQP were increased. |
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