Antarctic krill antioxidant peptides show inferior IgE-binding ability and RBL-2H3 cell degranulation

Enzymatic hydrolysis,isolation,and purification might make a great deal of difference in antioxidant activity and antigenicity of peptide components.This study aimed to isolate and purify antioxidant peptide components from Antarctic krill and evaluate their allergenicity of them.Electron paramagnetic resonance(EPR)spectroscopy results indicated 3-10 kDa Antarctic krill hydrolysates(AKHs)had higher DPPH and·OH radical scavenging rates.And the second component(N2-2)purified 3-10 kDa hydrolysate showed better ability to scavenge DPPH and·OH radicals(P<0.05),which were(47.43±2.18)%and(34.33±1.25)%,respectively.Additionally,indirect-ELISA results revealed that N2-1 had a weaker ability to bind specific IgE and that N2-2 had a lower binding capability to specific IgG1(P<0.05).And N2-2 had a higher EC50 value of(5.29±0.95)ng/mL(P<0.05)in cell degranulation assay,which was about 13.80 times that of Antarctic krill.Therefore,N2-2 might be the potential source of the antioxidant peptides with lower allergenicity.

Preparation and Antioxidative Effects of Soybean Peptides

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Effects of Peptides from Swine Blood on Antioxidative Capacity of Mice

Porcine peptides have strong antioxidative activities. The porcine peptides at different doses were administered hepatotoxic mice to investigate their in vivo antioxidant capability. After administration, the activity of superoxide dismutase and glutathione peroxidase in liver and serum was enhanced and malonaldehyde content in liver and serum was greatly decreased. Therefore, the porcine peptides can significantly reduce the damage of active oxygen to body, enhance the body＇s antioxidant capability, and thus maintain health.

Comparative Study on the Antioxidant Activity of Peptides from Pearl Oyster(Pinctada martensii) Mantle Type V Collagen and Tilapia(Oreochromis niloticus) Scale Type Ⅰ Collagen

In this study, Pearl oyster mantle type V collagen(POMC) and tilapia scale type I collagen(TSC) were extracted and hydrolyzed by various proteases in order to obtain peptides. The antioxidant activity of the peptides was investigated by DPPH, hydroxyl radical scavenging experiments and a dynamic digestion model in vitro. The results show that there are significant differences in amino acid composition between POMC and TSC. The collagen peptides obtained from pearl oyster mantle(POMCP) by treating with alkaline protease exhibited higher antioxidant activity than that from tilapia scale(TSCP) treated with papaya protease, and both of them showed greater DPPH and hydroxyl radical scavenging activity than other peptides. After being separated via Sephadex G-25 chromatography, the M1 fraction isolated from POMCP, and the S1 fraction from TSCP with which both had higher molecular weights showed the strongest antioxidant activity than other fractions, and the M1 fraction exhibited stronger antioxidant activity than the S1 fraction in scavenging free-radicals and protecting cells from the oxidation damage. Furthermore, after treating the dynamic digestion system model in vitro, the DPPH and hydroxyl radical scavenging activity of the M1 fraction increased slightly. These results suggest that POMCP exhibits stronger antioxidant activity than TSCP, which means that PMOP may be a good candidate to be a potential natural antioxidant in the food-processing industry.

Antioxidant peptides encrypted in flaxseed proteome:An in silico assessment

Flaxseed proteins and antioxidant peptides(AP)encrypted in their sequences were analysed in silico with a range of bioinformatics tools to study their physicochemical properties,allergenicity,and toxicity.Nine proteases(digestive,plant and microbial sources)were assessed for their ability to release known APs from 23 mature flaxseed storage proteins using the BIOPEP database.The families of proteins identified were predominantly globulins,oleosins,and small amount of conlinin.Overall,253 APs were identified from these proteins.More peptides were released by enzymatic hydrolysis from the globulins than those from oleosins and conlinin.Compared with other enzymes studied,the plant proteases(papain,ficin,and bromelain)were found to be superior to releasing APs from the flaxseed proteins.Analysis of toxicity by ToxinPred showed that none of the peptides released was toxic.Most of the APs showed structural features that are important for antioxidation,including relatively low molecular weight(dipeptides and tripeptides only);amphipathic properties(hydrophobicity range of-0.5 to+0.5);relatively low Boman index(≤2);broad range of pI(3.7-10.8),and an abundance of antioxidant amino acid residues(e.g.glutamic acid and histidine).This study demonstrate the suitability of flaxseed proteins as a source of APs.

Peptidomic analysis of whey protein hydrolysates and prediction of their antioxidant peptides

Enzymatic hydrolysis of proteins is a breakdown process of peptide bond in proteins,releasing some peptides with potential biological functions.Previous studies on enzymatic hydrolysis of whey proteins have not identified the complete peptide profiles after hydrolysis.In this study,we reconstructed a profile of peptides from whey hydrolysates with two enzymes and different processing conditions.We also developed an ensemble machine learning predictor to classify peptides obtained from whey hydrolysis.A total of 2572 peptides were identified over three process conditions with two enzymes in duplicate.499 peptides were classified and chosen as potential antioxidant peptides from whey proteins.The peptides classified as antioxidants in the hydrolysates had a proportion of 13.1%-24.5%regarding all peptides identified.These results facilitate the selection of promising peptides involved in the antioxidant properties during the enzymatic hydrolysis of whey proteins,aiding the discovery of novel antioxidant peptides.

Tartary buckwheat(Fagopyrum tataricum(L.)Gaertn)protein-derived antioxidant peptides:mechanisms of action and structure-activity relationship in Caco-2 cell models

Excessive reactive oxygen species(ROS)can cause oxidative damage and lead to various metabolic disease.Tartary buckwheat(Fagopyrum tataricum(L.)Gaertn)is a new kind of protein-rich functional food,the protein in which has been proved to have good antioxidant capacity.In this study,in order to further explore the antioxidant mechanism of Tartary buckwheat protein,4 peptides(CR-8,LR-8,GK-10 and SR-12)were isolated and identified from it.H2 O2 was used to induce oxidative damage to Caco-2 cells to evaluate antioxidant capacity of these peptides.The results of superoxide dismutase(SOD),total antioxidant capacity(T-AOC)and mitochondrial membrane potential etc.showed that these peptides have superior antioxidant capacity.CR-8 has the best antioxidant capacity.In order to further clarify the antioxidant mechanism of CR-8,metabolomics was used to analyze related metabolites and metabolic pathways.The results showed that after CR-8 intervention,the content of metabolites such as L-acetyl carnitine has increased.This indicated that CR-8 can improve the antioxidant capacity of damaged cells by intervening in multiple metabolic pathways.This also revealed the anti-oxidant mechanism of tartary buckwheat protein.In conclusion,it provided a theoretical basis for further studying the activity of tartary buckwheat portein and utilizing buckwheat resources.

Review on marine collagen peptides induce cancer cell apoptosis,necrosis,and autophagy by reducing oxidized free radicals

Marine collagen peptides(MCPs)are natural products prepared by hydrolyzing marine collagen protein through a variety of chemical methods or enzymes.MCPs have a range of structures and biological activities and are widely present in marine species.MCPs also have a small molecular weight,are easily modified,and absorbed by the body.These properties have attracted great interest from researchers studying antioxidant,anti-tumor,and anti-aging activities.MCPs of specific molecular weights have significant anti-tumor activity and no toxic side effects.Thus,MCPs have the potential use as anti-cancer adjuvant drugs.Free radicals produced by oxidation are closely related to human aging,cancer,arteriosclerosis,and other diseases,but their relationship with cancer is not well known.In this review,we focus on the antioxidant properties of MCPs in the treatment of cancer,highlighting their antioxidant molecular structure and potential for clinical practice.

Antifatigue,Antioxidant and Immunoregulatory Effects of Peptides Hydrolyzed from Manchurian Walnut(Juglans mandshurica Maxim.) on Mice

The Manchurian walnut(Juglans mandshurica Maxim.) is rich in proteins, whereas this resource has not been used efficiently. The antifatigue, antioxidative and immunoregulatory effects of Manchurian walnut hydrolysate peptides(MWHPs)were evaluated in this study. MWHPs with a degree of hydrolysis of 32.23% were ultrafiltered and divided into three fractions,namely, high(> 10 k Da), medium(3–10 kDa), and low molecular weight(< 3 kDa), and then fed to mice continuously at doses of 200, 400 or 800 mg/(kg·d). The antifatigue, antioxidative, and immunoregulatory effects of the peptides were tested on the second and fourth weeks of MWHP administration. Results showed that low-molecular-weight MWHPs exerted significant antifatigue(prolonging swimming time, elevating liver glycogen contents, and reducing lactic acid contents), antioxidative(enhancing superoxide dismutase(SOD), GSH-Px, and catalase(CAT) activities and reducing malondialdehyde(MDA) content), and immunoregulatory(raising the immune-organ index and promoting T-lymphocyte proliferation and s Ig A secretion in the intestinal tract) effects. This research indicates that MWHPs have potential applications in health care and may be developed as a base for new functional foods.

Purification and Identification of Antioxidant Peptides from the Scallop Skirts of Mimachlamys Nobilis

The processes of scallop meats can produce a large amount of by-products like scallop skirts,which are rich in nutrients. This work aimed to obtain the information about antioxidant peptides derived from scallop skirts of Mimachlamys nobilis. The hydro-lysates obtained by trypsin exhibited the highest antioxidant activity( 75.6%,79.5% and 76.7% using DPPH,hydroxyl and superoxide anion radical scavenging activity assays,respectively). The antioxidant peptides( MNAP) were separated and purified using UF membranes,GFC processes and RP-HPLC,and the antioxidant activity of MNAP was identified to be 85.7% using DPPH radical scavenging activity assay. The peptides( MNAP) were composed of two peptides with their molecular weights2 855.6 Da and 3 007.2 Da using MALDI-TOF-MS,respectively. The results suggested that the scallop skirts of Mimachlamys nobilis could be explored as a source of antioxidant peptides.

In vitro Antioxidant Effects of Porphyra haitanensis Peptides on H_2O_2-Induced Damage in HepG2 Cells

In this study,protein from Porphyra haitanensis was used as raw material to prepare an antioxidant peptide,and its antioxidant activity was evaluated in vitro.A model of H_2O_2-induced oxidative damage in Hep G2 cells was established,and the effects of Porphyra haitanensis hydrolysates (PHHs) on superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were detected.Finally,the structure of PHHs was identified by ESI-MS/MS.The results showed that the 1,1-diphenyl-2-pyridylhydrazine(DPPH)-free radical-scavenging ability of PHHs was the strongest (59.28%at 1.0 mg m L~(-1)) when hydrolyzed with an acidic protease for 4 h.PHHs with different concentrations had protective effects on H_2O_2-induced damage to Hep G2 cells,and the protective effect was enhanced with increasing concentrations.When the level was 400μg m L~(-1),the cell survival rate was as high as 88.62%.Moreover,PHHs can significantly reduce oxidative damage to Hep G2 cells by H_2O_2,improve SOD activity,and reduce MDA content.The tetrapeptide Asp-Lys-Ser-Thr,with a molecular weight of 448 Da,was identified as an important fraction of PHHs by high-resolution mass spectrometry.

Changes of the Content and Antioxidant Activity of Natural Peptides in Germinated Soybeans

[ Objective] This study aimed to investigate the content and antioxidant activity of natural peptides in various soybean sprouts during the germination process. [Method] By using black soybean sprouts, yellow soybean sprouts and green soybean sprouts as raw materials, the content, DPPH ·clearance rate, OH · clearance rate and reduction capacity of natural peptides in various soybean sprouts at different germination time were determined, to evaluate the antioxidant capacity of natural peptides and compare it with that of Vc. [ Result] The results showed that the contents of natural peptides in black soybean sprouts, yellow soybean sprouts and green soybean sprouts varied at different germination time. To be specific, the content of natural peptides in black soybean sprouts reached the maximmn of 0. 194 mg/g at 2 d post-germination; the content of natural pepfides in yellow soybean sprouts reached the maximum of 0.231 mg/g at 2 d post-germination; the content of natural peptides in green soybean sprouts exhibited a negative correlation with the germination time, which reached the maximum of 0. 164 mg/g at 1 d post-germination. [ Conclusion] According to the determination of DPPH ·clearance rate, OH ·clearance rate and reduction capacity of natural peptides in three varieties of soybean sprouts, natural peptides in yellow soybean sprouts possess the highest antioxidant activity, followed by those in black soybean

Novel Antioxidant Peptides Derived from Enzymatic Hydrolysates of Macadamia Protein

In the present work, macadamia protein was enzymatic hydrolyzed to produce peptides which had abundant antioxidant activities. The relative antioxidant capacity was investigated through some in vitro models such as scavenging activity of DPPH radical, scavenging of ABTS+ radical and evaluation of the total antioxidant capacity assay. Macadamia protein was characterized by methods of DEAE cellulose cation-exchange chromatography and SDS-PAGE. Besides, method of price graph was used to compare the difference and to investigate the connection between the actual and ideal antioxidant value of the hydrolysates, aiming to reduce this difference.

Production and Purification of Antioxidant Peptides from Flatfish Skin Protein Hydrolysates

Antioxidant peptides of flatfish skin protein hydrolyzed by four enzymes(Papain, Pepsin, Trypsin and Neutrase, respectively)were investigated. The Trypsin hydrolysate obtained by hydrolysis exhibited the highest 1,1-dipheny-l-2-picrylhydrazyl(DPPH)radical scavenging activity(DRSA)compared with other hydrolysates. Response surface method ology(RSM), based on Box-Behnken design, was used to study the influence of hydrolysis conditions on the DRSA. The optimal hydrolysis conditions were as follows: p H 7.38, temperature 48.2℃ and enzyme/substrate(E/S)ratio 2 840 U/g. Under these conditions, the maximum DRSA was(22.85 ± 0.57)%,. The experimental values agreed with the value(23.09%,)predicted by the model within a 95%, confidence interval. By using gel filtration chromatography and reversed-phase high performance liquid chromatography(RP-HPLC), antioxidant peptide(D2-P)was isolated from flatfish skin protein hydrolysates(FSPH)and could exhibit a(54.28 ± 1.37)%, scavenging activity on DPPH radical at the concentration of 5 mg/m L. This is the first report of a scientific basis for the preparation of antioxidant peptides from flatfish skin. The results suggested that the antioxidant peptides can be exploited into functional foods or used as a novel source of nutraceuticals.

Study on the Molecular Weight Composition and Antioxidant Activity of Peanut Bioactive Peptides

[Objective]To prepare peanut bioactive peptides and analyze their molecular weight composition and antioxidant activity.[Method]The dialysis bag of 8.0,3.5 and 1.0 kD were used to classify the hydrolyzate derived from alcalase and flavourzyme,peanut bioactive peptides of different molecular weight were obtained and then their scavenging capacity of free radicals was measured.The molecular weight composition was studied by Tricine-SDS-PAGE.[Result]The content of peptides <1.0 kD were 76.21% and 83.42% in the total hydrolyzate from alcalase and flavourzyme respectively.All hydrolyzate with different molecular grades showed free radical scavenging capacity,which was increased with the reduction of molecular mass.The peptides <1.0 kD exhibited higher radical scavenging capacity of(87.41±0.66)%(alcalase)and(67.88±0.48)%(flavourzyme),respectively.[Conclusion]Peanut bioactive peptides had strong effect of antioxidant capacity,especially that <1.0 kD,which had great prospect.

Screening of protease-producing marine yeasts for production of the bioactive peptides

Over 400 yeast strains from seawater and sediments were obtained, but only five strains named HN2 -3, N13d, N13C, Mb5 and HN3 - 2 among them could form clear zones around their colonies on the double plates with 2.0% casein. Peptides in the hydrolysate produced by the proteases from strains HN2 -3 and N13d had higher angiotensin I-converting-enzyme （ACE）-inhibitory activity. The two marine yeast strains were identified to be Aureobasidium pullulans according to the results of routine yeast identification and molecular methods. After purification of the proteases from the two marine yeast strains, it was found that the optimal pH for them was both 9.0, both of them were serine alkaline protease. However, the optimal temperature for the protease from the strain HN2 -3 was 52℃ while that from strain N13d was 48℃. ACE-inhibitory activity of the peptides in the hydrolysate of shrimp protein produced by the purified protease from the strain HN2 -3 was the highest while antioxidant activity in the hydrolysate of spirulina protein produced by the purified protease from the strain N13d was the highest.

The protective effects of peptides from Chinese baijiu on AAPH-induced oxidative stress in HepG2 cells via Nrf2 signaling pathway

Antioxidant peptides have been widely reported.However,only a few reports have been published examining the antioxidant peptides derived from Chinese baijiu.In this study,6 novel peptides derived from Chinese baijiu were identified successfully using high-performance liquid chromatography-quadrupoletime-of-flight mass spectrometry(HPLC-QTOF-MS)with a concentration of 0.835–24.540μg/L.The underlying molecular mechanisms were investigated,and their cytoprotective effects were examined against 2,2’-azobis(2-methylpropanimidamidine)dihydrochloride(AAPH)-induced oxidative stress in Hep G2 cells.The results showed that these peptides exerted protective effects by suppressing reactive oxygen species(ROS)generation,preventing malondialdehyde(MDA)formation,and upregulating cellular antioxidant enzyme activities(SOD,CAT,and GSH-Px)in a dose-dependent manner.Further experiments proved that these peptides exerted antioxidant effects via Nrf2/ARE-mediated signaling pathway by promoting Nrf2 nuclear translocation,inhibiting ubiquitination,and enhancing transcription capacity of Nrf2 in Hep G2 cells.These findings provide the molecular basis for the effects of antioxidant peptides derived from Chinese baijiu,which is important for a deeper understanding of the relationship between human health and moderate drinking.

Solid-Phase Enzymatic Peptide Synthesis to Produce an Antioxidant Dipeptide

Peptide bond synthesis is favorable to the production of bioactive small peptides. However, the abuse of toxic reagents remains an issue for chemical synthesis method, whereas the low product yield and purity limit the widespread use of enzymatic method. In this study, a new solid-phase enzymatic peptide synthesis(SPEPS) strategy was developed to produce an antioxidant tyrosine-alanine dipeptide(Tyr-Ala) by using recombinant carboxypeptidase Y(CPY) as the catalyst. The general SPEPS procedure involves three steps. First, the N-protected acyl donor was covalently attached to solid resin. Second,the peptide bond was condensed between the acyl donor and the nucleophile under the catalysis of CPY. Finally, one-step cleavage was performed to remove the protecting group and cleave the peptides from solid resin. Upon the optimization of reaction conditions, 77.92%(±2.723%) yield of Tyr-Ala with high product purity of 90.971%(±2.695%) was obtained.In addition, the antioxidant activity of Tyr-Ala was determined by ABTS method, indicating that the synthesized Tyr-Ala obtained by SPEPS showed a superior antioxidant capability compared with commercial glutathione.

Protective effects of peptide KSPLY derived from Hericium erinaceus on H_(2)O_(2)-induced oxidative damage in HepG2 cells

Reactive oxygen species(ROS)-induced oxidative damage is strongly associated with the pathogenesis of chronic diseases,and natural antioxidant peptides have good abilities of scavenging ROS.The antioxidant activity of peptide Lys-Ser-Pro-Leu-Tyr(KSPLY)derived from Hericium erinaceus remains unclear.In the present study,the antioxidant effect and mechanism of KSPLY on H_(2)O_(2)-induced oxidative damage in HepG2 cells were investigated.The results indicated that KSPLY exhibited the antioxidant capacity in H_(2)O_(2)-induced HepG2 cells by enhancing superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),and catalase(CAT)activities.In comparison with the H_(2)O_(2)-treated damage group,the apoptosis rate,ROS level,and malondialdehyde(MDA)content of HepG2 cells treated with KSPLY were significantly decreased.The H.erinaceus-derived peptide KSPLY pretreatment promoted the expression of detoxification and antioxidant enzymes via the Keap1/Nrf2 signal pathway,thereby inhibiting the generation of ROS and MDA.In conclusion,the H.erinaceus-derived peptide KSPLY effectively protected HepG2 cells against H_(2)O_(2)-induced oxidative damage,and it provided a theoretical basis for the further development of new natural antioxidants.