A novel antioxidant and antimicrobial peptide from hen egg white lysozyme hydrolysates

Hen egg white lysozyme (HEWL) was hydrolyzed with papain, trypsin and a combination of the two to isolate antioxidant peptides. The prepared hydrolysates were evaluated for antioxidant activity using DPPH and ABTS radical scavenging, metal ion chelation and lipid peroxidation inhibition. The obtained hydrolysate by a combination of the two enzymes exhibited the highest antioxidant activity compared to other hydrolysates and elected for isolation of antioxidant peptides by reverse-phase high-performance liquid chromatography (RP-HPLC). A most potent fraction namely F2 fraction, identified to be NTDGSTDYGILQINSR (MW: 1753.98 ± 0.5 Da) using tandem mass spectrometry. The antimicrobial activity of the F2 peptide was tested using radial diffusion assay (RDA). Our results showed that this peptide has inhibitory effects on both Gram-negative and Gram-positive bacteria. Minimum inhibition concentration (MIC) values of the F2 peptide against Escherichia coli and Leuconostoc mesenteroides bacteria were 355.64 (±2.2) and 442.25 (±2.8) μg/ml, respectively.     

Purification and identification of antioxidant peptides from corn gluten meal

Corn gluten meal was hydrolyzed by alkaline protease and Flavourzyme to obtain the antioxidant peptides. The antioxidant activities of the hydrolysates or peptides were evaluated by free radical scavenging capacity (1,1-diphenyl-2-picrylhydrazyl/2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt/hydroxyl radical/superoxide radical anion), metal ion (Fe²⁺/Cu²⁺) chelating activity and lipid peroxidation inhibitory capacity. The hydrolysates were separated by ultrafiltration, and those with molecular weight <10 kDa exhibited highest antioxidant activity in all relevant assays. The hydrolysates were subsequently purified by gel filtration chromatography, and fraction F3 showed the highest antioxidant activity. Three peptides were identified from fraction F3 using LC–ESI–Q–TOF MS/MS as Leu-Pro-Phe (375.46 Da), Leu-Leu-Pro-Phe (488.64 Da) and Phe-Leu-Pro-Phe (522.64 Da). These peptides exhibited good free radical scavenging activity and lipid peroxidation inhibitory effect. Thus, corn gluten meal may be used as a potential source of antioxidant peptides for food and nutraceutical applications.     

Screening of whey protein isolate hydrolysates for their dual functionality: Influence of heat pre-treatment and enzyme specificity

Heat pre-treated and non heat pre-treated whey protein isolate (WPI) were hydrolysed using α-chymotrypsin (chymotrypsin), pepsin and trypsin. The in vitro antioxidant activity, ACE-inhibition activity and surface hydrophobicities of the hydrolysates were measured in order to determine if peptides with dual functionalities were present. Dual functional peptides have both biological (e.g. antioxidant, ACE-inhibition, opioid activities) and technological (e.g. nanoemulsification abilities) functions in food systems. Heat pre-treatment marginally enhanced the hydrolysis of WPI by pepsin and trypsin but had no effect on WPI hydrolysis with chymotrypsin. With the exception of the hydrolysis by trypsin, heat pre-treatment did not affect the peptide profile of the hydrolysates as analysed using size exclusion chromatography, or the antioxidant activity (P > 0.05). Heat pre-treatment significantly affected the ACE-inhibition activities and the surface hydrophobicities of the hydrolysates (P < 0.05), which was a function of the specificity of the hydrolysing enzyme. Extended hydrolysis (up to 24 h) had no significant effect on the DH and the molecular weight profiles (P > 0.05) but in some instances caused a reduction in the antioxidant activity of WPI hydrolysates. The chymotrypsin hydrolysate showed a broad MW size range, and was followed by pepsin and then trypsin. The bioactivities of the hydrolysates generally decreased in the order; chymotrypsin > trypsin > pepsin. This study showed that by manipulating protein conformation with pre-hydrolysis heat treatment, combined with careful enzyme selection, peptides with dual functionalities can be produced from WPI for use as functional ingredients in the manufacture of functional foods.     

Release of multifunctional peptides by gastrointestinal digestion of sea cucumber (Isostichopus badionotus)

Sea cucumber is a benthic marine organism distributed worldwide and used as food in several Asian countries. The species Isostichopus badionotus is captured intensively off the Yucatan Peninsula, Mexico. Boiled I. badionotus was subjected to in vitro simulated gastrointestinal digestion using pepsin and a pepsin–Corolase PP^® mixture. ACE-inhibitory and radical scavenging activities, iron reducing capacity and cytotoxic effects against colorectal cancer cells were evaluated in the hydrolysates and their ultrafiltered fractions. ACE-inhibitory activity was potent in fractions containing peptides <3000 Da, an effect augmented with combined action of gastric (pepsin) and intestinal (Corolase PP^®) enzymes (IC₅₀ = 0.038 ± 0.004 mg/mL). Antioxidant activity was exerted by peptides with low and high molecular weights, depending on hydrolysis method. This is the first report of cytotoxic capacity against colorectal HT-29 cells in peptides from sea cucumber. Sea cucumber hydrolysates and ultrafiltered fractions are potential ingredients for development of functional foods.     

Obtaining of Brassica carinata protein hydrolysates enriched in bioactive peptides using immobilized digestive proteases

Brassica carinata protein hydrolysates were obtained by sequential hydrolysis with immobilized trypsin, chymotrypsin, and carboxypeptidase A on glioxyl-agarose supports. The final protein hydrolysate with a 36% degree of hydrolysis was made up of peptides smaller than 15 kDa. Three peptide fractions were obtained after gel filtration chromatography and antioxidative, hypocholesterolemic, and inhibitory of angiotensin converting enzyme activities were assayed in comparison with the starting materials (protein isolate and hydrolysate). Total protein hydrolysate achieved the best results in the reduction of micellar cholesterol and fraction II, composed by peptides between 1800 and 1400 Da, showed the best antioxidant and inhibitory of angiotensin converting enzyme activities. These results show that B. carinata seed proteins may represent an useful source of bioactive peptides after hydrolysis with digestive proteases such as trypsin, chymotrypsin, and carboxypeptidase A.     

Structure–mechanism relationship of antioxidant and ACE I inhibitory peptides from wheat gluten hydrolysate fractionated by pH

The aims of this study were to assess bioactive properties (ACE inhibition and antioxidant capacity) from wheat gluten hydrolysate peptides fractionated by pH (4.0, 6.0 and 9.0), to determine peptide action mechanism, and to relate it to the secondary structure and functional groups of peptides. Gluten hydrolysate extracts (GHE) were enriched in peptides with medium hydrophobicity and molecular weight (≈ 60% MH and 5.5 kDa, respectively). Gluten peptides inhibited ACE I by uncompetitive mechanism and a direct relationship between α-helix structure and IC50% value was obtained (r = 0.9127). TEAC and cooper chelating activity from GHE 6.5 were the highest and directly correlated with MH peptides. GHE 9.0 had high carotene bleaching inhibition (47.5 ± 0.3%) and reducing power activity (163.1 ± 2.9 mg S₂O₃^2 − equivalent g^− 1 protein), which were directly related to disulfide bonds content of peptides (r = 0.9982 and 0.9216, respectively). pH was a good alternative to select bioactive peptides from wheat gluten hydrolysate.     

Angiotensin I-converting enzyme inhibitory activity of chickpea and pea protein hydrolysates

ACE inhibitory activity was studied for different hydrolysates obtained from protein concentrates of chickpea (kabuli and desi) and yellow pea (Golden) using in vitro gastrointestinal simulation, alcalase/flavourzyme, and papain. Protein/peptide profiles studied by SDS–PAGE and SE-HPLC, showed a rich composition of the hydrolysates in small peptides having MWs under 4 kDa. Papain hydrolysed yellow pea proteins showed the highest ACE inhibitory activity. In addition, chickpea desi proteins hydrolysed by in vitro gastrointestinal simulation showed higher ACE inhibition (IC₅₀ of 140 ± 1 μg/ml) compared to its digests obtained by alcalase/flavourzyme (IC₅₀ of 228 ± 3 μg/ml) or papain (IC₅₀ of 180 ± 1 μg/ml) and to chickpea kabuli hydrolysed by gastrointestinal simulation (IC₅₀ of 229 ± 1 μg/ml). The results demonstrate that enzymatic hydrolysates of chickpea and pea proteins contain bioactive ACE inhibitory peptides; furthermore, the type of enzyme used for hydrolysis affects the ACE inhibitory activity.     

Antioxidative properties of peptides prepared from tuna cooking juice hydrolysates with orientase (Bacillus subtilis)

The antioxidative activity of isolated peptides from of tuna cooking juice hydrolysates by orientase was determined. The results showed that, among the hydrolysates obtained under different hydrolysis time, the highest antioxidative activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity were presented at 60 min. Then, the protein hydrolysate was subjected to a Sephadex G-25 gel filtration chromatography, and five major fractions were obtained. Peptide fractions ranging from 400 to 1500 Da showed the highest antioxidative activity among all fractions. The peptide fractions were further isolated using the two-step high performance liquid chromatography (HPLC-1 and HPLC-2), and six and three fractions were obtained, respectively. The final three antioxidative peptides comprised 4–10 amino acids sequences were observed, and the structures of the peptides were Pro-Val-Ser-His-Asp-His-Ala-Pro-Glu-Tyr (1305 Da), Pro-Ser-Asp-His-Asp-His-Glu (938 Da), and Val-His-Asp-Tyr (584 Da), respectively. We thus conclude that antioxidative hydrolysates from tuna cooking juice may be useful ingredients in food and nutraceutical applications.     

Production,analysis and in vivo evaluation of novel angiotensin-I-converting enzyme inhibitory peptides from bovine casein

Novel angiotensin-I-converting enzyme inhibitory peptides were isolated from bovine casein hydrolysate prepared by AS1.398 neutral protease. The active hydrolysate obtained at 12 h hydrolysis showed the highest ACE-inhibitory activity and was further consecutively separated by ultrafiltration, and the 3 kDa permeate showed the highest ACE-inhibiting activity. This active fraction was further purified to yield two novel ACE-inhibiting peptides, whose amino acid sequences were Arg-Tyr-Pro-Ser-Tyr-Gly (κ-casein; f25–30) and Asp-Glu-Arg-Phe (κ-casein; f15–18), respectively. The IC₅₀ value of the peptides were 54 ± 1.2 μg/mL and 21 ± 0.8 μg/mL, respectively. The Lineweaver–Burk plots revealed that the peptides acts as a non-competitive inhibitor. Antihypertensive effect in spontaneously hypertensive rats also revealed that single and repeated oral administrations of hydrolysates of bovine casein decreased systolic blood pressure significantly in spontaneously hypertensive rats (P < 0.01, P < 0.05). These results suggested that the peptide derived from peptides from bovine casein would be a beneficial ingredient for functional food or pharmaceuticals against hypertension.     

Antioxidant activities of enzymatic rapeseed protein hydrolysates and the membrane ultrafiltration fractions

In this study, rapeseed protein isolate was hydrolyzed with various proteases to obtain hydrolysates that were separated by membrane ultrafiltration into four molecular size fractions (<1, 1–3, 3–5, and 5–10 kDa). Alcalase hydrolysis significantly (p < 0.05) produced the highest yield of protein hydrolysate while Flavourzyme produced the least. The <1 kDa fraction was the most abundant after the membrane ultrafiltration of the protein hydrolysates, which indicates that the proteases were efficient at reducing the native rapeseed proteins into low molecular weight peptides. Antioxidant properties of the resulting hydrolysates and membrane fractions were characterized and results showed the Pepsin + Pancreatin (P + P) protein hydrolysate had significantly highest (p < 0.05) scavenging activity against DPPH radical among the unfractionated enzymatic hydrolysates. But the P + P hydrolysate was not as effective as other hydrolysates during long-term inhibition of linoleic acid oxidation. For most of the samples, fractionation into the <1 kDa peptides significantly (p < 0.05) improved DPPH and superoxide scavenging properties when compared to the unfractionated protein hydrolysates. Only the <1 kDa fraction showed ferric reducing antioxidant power and the effect was dose-dependent. Overall, Alcalase and Proteinase K seem to be more efficient proteases to release antioxidant peptides from rapeseed proteins when compared to P + P, Flavourzyme and Thermolysin.     

Purification and identification of antioxidative peptides from loach (Misgurnus anguillicaudatus) protein hydrolysate by consecutive chromatography and electrospray ionization-mass spectrometry

Loach protein was hydrolyzed by papain to obtain antioxidative peptides. The results showed that the loach protein hydrolysate (LPH) could scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) (IC₅₀ = 17.0 ± 0.54 mg/mL) and hydroxyl radicals (IC₅₀ = 2.64 ± 0.29 mg/mL). It could chelate cupric ion and inhibit the lipid peroxidation in a linoleic acid emulsion system. The hydrolysate was isolated and purified by ultrafiltration and consecutive chromatographic methods including ion-exchange chromatography, gel filtration chromatography and a two-step reverse high-performance liquid chromatography (RP-HPLC). The purified antioxidant peptide was identified as Pro-Ser-Tyr-Val (464.2 Da) using RP-HPLC connected on-line to an electrospray ionization (ESI) mass spectrometer. The purified peptide showed a 9.14-fold higher scavenging activity for hydroxyl radical compared with the crude LPH. Therefore, it is possible to produce natural antioxidative peptides from loach protein by enzymatic hydrolysis and purification.     

Purification and characterization of angiotensin I converting enzyme inhibitory peptides from jellyfish Rhopilema esculentum

Two angiotensin I converting enzyme (ACE) inhibitory peptides were isolated from jellyfish Rhopilema esculentum protein hydrolysates prepared with pepsin and papain. Consecutive purification methods, including ion-exchange chromatography, size-exclusion chromatography and reverse-phase high-performance liquid chromatography, were used for isolation of ACE inhibitory peptides. The amino acid sequence of the peptides was identified as Gln-Pro-Gly-Pro-Thr and Gly-Asp-Ile-Gly-Tyr, respectively, and the IC₅₀ value of the purified peptides for ACE inhibitory activity was 80.67 μM and 32.56 μM. The purified peptides were evaluated for the antihypertensive effect in spontaneously hypertensive rats (SHR) after oral administration. Blood pressure decreased significantly after ingestion of the peptides. The results suggest that peptides derived from jellyfish R. esculentum may be beneficial as antihypertensive compounds in functional food resources.     

Three novel angiotensin I-converting enzyme (ACE) inhibitory peptides from cuttlefish (Sepia officinalis) using digestive proteases

The angiotensin I-converting enzyme (ACE) inhibitory activities of protein hydrolysates prepared from muscle of cuttlefish (Sepia officinalis) by treatment with various digestive proteases were investigated. The most active hydrolysate was obtained with the crude protease extract from the hepatopancreas of cuttlefish (64.47 ± 1.0% at 2 mg of dry weight/ml) with a degree of hydrolysis of 8%. By gel filtration on Sephadex G-25 and RP-HPLC on C18 column, three novel peptides with high ACE-inhibitory activity were purified and their molecular masses and amino acid sequences were determined. The three peptides Val-Tyr-Ala-Pro, Val-Ile-Ile-Phe and Met-Ala-Trp with IC₅₀ values of 6.1, 8.7 and 16.32 μM, respectively, were novel ACE-inhibitory peptides. Lineweaver–Burk plots suggest that the three purified peptides act as non-competitive inhibitors against ACE. These results suggest that some peptides from cuttlefish could be a beneficial ingredient for nutraceuticals against hypertension.     

Influence of marine oligosaccharides on the response of various biological systems to UV irradiation

Low molecular weight alginate-derived oligosaccharide (ADO) (373–571 Da) and chito-oligosaccharide (COS) (855–1671 Da) were purified from alginate and chitosan, and known as marine oligosaccharides with polyanionic and polycationic properties, respectively. We compared the effects of ADO and COS on cell regulation using several biological models (Candida albicans, Escherichia coli and Bacillus subtilis spore), cellular uptake determination, erythrocytes haemolysis inhibition and antioxidant capacity assay to investigate stress response under UV radiation. Our results further confirmed the anti-UVR potential of ADO and COS and their potential for commercial UVR protector application in the area of functional foods as food ingredients.     

Purification of novel anti-inflammatory peptides from enzymatic hydrolysate of the edible microalgal Spirulina maxima

Natural bioactive peptides have been known as ingredients in nutraceuticals and pharmaceuticals. In this study, the potential anti-inflammatory peptides were purified from enzymatic hydrolysate of the edible microalgae Spirulina maxima using gastrointestinal endopeptidases (trypsin, α-chymotrypsin, and pepsin). Purification of the hydrolysate resulted in two peptides with amino acid sequences of LDAVNR (P1, 686 Da) and MMLDF (P2, 655 Da). It was found that peptides P1 and P2 exhibited significant inhibition on the release and production of histamine from antigen-stimulated RBL-2H3 mast cells. Moreover, the suppressive effect of P1 and P2 on production as well as expression of interleukin-8 in histamine-stimulated EA.hy926 endothelial cells was determined. Notably, the production of intracellular reactive oxygen species from mast cells and endothelial cells was decreased in the presence of P1 or P2. Collectively, the peptides P1 and P2 from S. maxima could be used as functional ingredients with potent anti-inflammatory benefits.     

Subcritical water extraction of phytochemicals from Phlomis umbrosa Turcz

Subcritical water extraction (SWE) avoids the use of organic solvents when extracting active compounds. The SWE of phytochemicals from Phlomis umbrosa Turcz (PT) and the effect of antioxidant activity were investigated while varying the extraction temperature (from 100 °C to 200 °C) and time (from 5 to 25 min). The maximum yields of total polyphenols (142.02 ± 5.67 mg/g PT, mean ± SD) and flavonoids (33.69 ± 3.01 mg/g PT) were obtained for an extraction temperature and time of 200 °C and 20 min, respectively. The correlation of antioxidant activities in terms of their total phenolics and flavonoids contents suggest that the ABTS⁺ assay better reflects the antioxidant contents in SWE from PT than does the DPPH assay for extraction temperatures from 110 °C to 200 °C. At higher temperatures around 200 °C, SWE extracts affect the antioxidant activity due to the presence of not only flavonoids but also nonflavonoid phenolic compounds including prenylated flavonoids.Industrial relevanceThis study used subcritical water extraction (SWE) for the practical applications of the SWE process that extracts antioxidant compounds from medicinal herb such as Phlomis umbrosa Turcz. SWE is excellent technology to selectively extract bioactive compounds using temperature-dependent dielectric constant properties of water. As the temperature of water is increased, the polarity of water decreases. That's why it is selective extraction. The use of SWE in the present study was associated with high efficiency and antioxidant activities. These results indicate that SWE is an efficient and rapid method for extracting phytochemicals, and a safer product only using purified water. SWE has a potential to develop a commercial process for the extraction of phytochemicals. This method can be easily implemented on an industrial scale.     

Isolation and characterization of three antioxidant pentapeptides from protein hydrolysate of monkfish (Lophius litulon) muscle

In the current study, an efficient method had been developed to acquire the antioxidant hydrolysate of monkfish muscle protein (MPH) using trypsin by an orthogonal (L₉(3)⁴) test. Under the optimum conditions of enzymolysis time 4 h, enzyme-to-substrate ratio (E/S) 2%, enzymolysis temperature 40 °C and pH 8.0, the DH (Degree of hydrolysis) and hydroxyl radical scavenging activity of MPH reached 19.83 ± 0.82% and 58.05 ± 3.01%, respectively. By using ultrafiltration, gel filtration chromatography and reversed phase high performance liquid chromatography (RP-HPLC), three antioxidant pentapeptides were isolated from MPH, and their amino acid sequences were identified as Glu-Trp-Pro-Ala-Gln (MPH-P1), Phe-Leu-His-Arg-Pro (MPH-P2), and Leu-Met-Gly-Gln-Trp (MPH-P3) with molecular weights of 629.68 Da, 668.80 Da, and 633.77 Da, respectively. MPH-P1, MPH-P2, and MPH-P3 exhibited good scavenging activities on hydroxyl radical (EC₅₀ 0.269, 0.114 and 0.040 mg/ml), DPPH radical (EC₅₀ 2.408, 3.751, and 1.399 mg/ml), and superoxide anion radical (EC₅₀ 0.624, 0.101, and 0.042 mg/ml) in a dose-dependent manner. MPH-P3 was also effective against lipid peroxidation in the model system. The antioxidant activities of MPH-P1, MPH-P2, and MPH-P3 were due to their small sizes and the presence of antioxidant and hydrophobic amino acid residues within their sequences. The results of this study suggested that the protein hydrolysate and/or its isolated peptides might be effectively used as food additives for retarding lipid peroxidation occurring in foodstuffs.     

Identification and characterization of antioxidant peptides from sweet potato protein hydrolysates by Alcalase under high hydrostatic pressure

Sweet potato protein hydrolysates (SPPH) were generated by Alcalase under high hydrostatic pressure (HHP, 100, 200 and 300 MPa). HHP significantly improved the degree of hydrolysis (DH) and antioxidant activity, and increased the < 3 kDa fraction content of SPPH (P < 0.05). SPPH by Alcalase at 300 MPa for 60 min exhibited the highest DH and antioxidant activity and was separated into three fractions by ultrafiltration. The most active fraction FIII (< 3 kDa) was further separated into fifty four fractions by semi-preparative RP-HPLC and measured using the ORAC assay. In addition, more active fractions were examined by LC–MS/MS, and diverse peptides were identified, matching sequences of Sporamins A and B. To evaluate the structure–activity dependences, twenty sequences were synthesized, of which the antioxidant activity was assessed. Five peptides showed good activity: HDSASGQY ≥ YYMVSA ≥ HDSESGQY ~ YYIVS ~ RYYDPL, with the contribution of His and Tyr.Industrial relevanceThis study will give a novel technique for using industrial waste slurry, a byproduct in the process of sweet potato starch manufacturing, which contains various bioactive components (such as protein, minerals, etc.) since most of them are normally discarded. The present study is focused on assessing the effects of enzymatic hydrolysis by Alcalase under high hydrostatic pressure (HHP) on the release of antioxidant peptides from sweet potato protein (SPP). The results of this work provide a potential application of enzymatic hydrolysis assisted by HHP on the development of ingredients from SPP in functional foods.     

Effects of controlled pepsin hydrolysis on antioxidant potential and fractional changes of chickpea proteins

This study investigated the effects of controlled pepsin hydrolysis on antioxidant potential and fractional changes of chickpea protein extracts (CPE). The enzyme hydrolysis increased soluble protein content (1.2 to 2-fold) and free radical scavenging activity (1.9 to 3-fold) of hydrolyzed chickpea protein extract (HCPE), but almost unaffected its antioxidant potential in oil-in-water emulsion system and reduced its iron chelating capacity (1.3-fold) and functional properties. The chromatographic fractions of CPE are mainly acidic, while those of HCPE are mainly basic and neutral. The majority of chickpea proteins had pI between 4.5 and 5.5, and molecular weight (MW) between 15 and 40 kDa, while MW of their pepsin hydrolysis products ranged between 6.5 and 14.2 kDa. The main antioxidant proteins in CPE and HCPE fractionated by ultrafiltration had MW greater than 30 kDa and between 2 and 10 kDa, respectively. The chickpea proteins and hydrolysates showed different potentials as functional food ingredients.     

Purification and identification of three novel antioxidant peptides from protein hydrolysate of bluefin leatherjacket (Navodon septentrionalis) skin

Skin protein from a bluefin leatherjacket (Navodon septentrionalis) processing by-product was hydrolyzed by trypsin, flavourzyme, neutrase, papain, alcalase, and pepsin, and protein hydrolysate (BSH) prepared using alcalase showed the highest DPPH, HO, and O₂⁻ · scavenging activities among all hydrolysates. Using ultrafiltration and consecutive chromatography, three novel peptides with strong antioxidant properties were purified from BSH, and their sequences were determined as Gly-Ser-Gly-Gly-Leu (GSGGL, BSP-A), Gly-Pro-Gly-Gly-Phe-Ile (GPGGFI, BSP-B), and Phe-Ile-Gly-Pro (FIGP, BSP-C) with molecular weights of 389.41, 546.63, and 432.52 Da, respectively. BSP-C exhibited the highest scavenging activities on DPPH (EC₅₀ 0.118 mg/ml), HO (EC₅₀ 0.073 mg/ml), and O₂⁻ · (EC₅₀ 0.311 mg/ml) among the three peptides. In addition, BSP-C could effectively inhibit autooxidation in a linoleic acid model system. The antioxidant activities of BSP-A, BSP-B, and BSP-C might be due to the small molecular sizes and the hydrophobic and/or aromatic amino acid residues in their amino acid sequences. The present results suggested that peptides purified from the skin protein hydrolysate of bluefin leatherjacket were excellent antioxidants and could be effectively used as food ingredients and additives, and pharmaceuticals.