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Background: Oratosquilla woodmasoni is one of the marine squilla species, which is found in the entire Asia-Pacific region. This current study assesses the species as the main basis of both ACEi and antioxidant peptide. Objective: To isolate the ACEi peptide derived from O. woodmasoni and examine its ACE inhibition along with antioxidant potential. Materials and Methods: The squilla muscle protein was hydrolysed using alcalase and trypsin enzymes for 12 hours and tested for DH. The hydrolysates were examined for their ACEi activity and then the best hydrolysate was sequentially purified in various chromatographical methods. The purified peptide was studied for anti-oxidant and functional properties, followed by amino acid sequencing. The purified peptide was also evaluated for its toxicity by in vitro cell viability assay. Results: The DH% was found to be 47.13 ± 0.72% and 89.43 ± 2.06% for alcalase and trypsin, respectively. The alcalase 5th-hour hydrolysate was detected with potent activity (65.97 ± 0.56%) using ACEi assay and was primarily fractionated using ultrafiltration; the maximum inhibitory activity was found with 77.04 ± 0.52% in 3-10 kDa fraction. Subsequently, the fraction was purified using IEC and GFC, in which the AC1-A2 fraction had higher antihypertensive activity (70.85 ± 0.78%). The non-toxic fraction showed hexapeptide HVGGCG with molecular weight 529 Da with great potential of antioxidant activity along with functional property. Conclusion: This peptide could be developed as a potential ACE-inhibitory and antioxidant agent.

Background: Green mussel Perna viridis is a bivalve mollusc which is native to the Indian coast and can be found in the Indo-Pacific as well as Asia-Pacific regions. This study evaluates the P. viridis foot (PVF) as a source of an anti-inflammatory peptide. Objective: To characterize and evaluate the possibility of pro-inflammatory cytokines, nitric oxide (NO) as well as cyclooxygenase (COX)-2 reduction in RAW264.7 cells and to analyze functional aspects of the derived peptide from PVF. Materials and Methods: The PVF was hydrolysed with different enzymes and the antiinflammatory activity of hour hydrolysates were evaluated using HRBC Membrane Stabilization (HMS) against hypotonicity induced haemolysis and Albumin Denaturation (AD) inhibition from induced heat assays. Later, the active hour hydrolysate was separated by ultrafiltration and purified using Size-Exclusion Chromatography (SEC). Further, the purified peptide’s sequence was identified using LC-MS/MS and functional properties were determined. Also, the peptide was observed for its anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated RAW264.7 cells for pro-inflammatory cytokines, NO production and COX-2 activation. Results: Among the four enzymes 6th hour alcalase hydrolysate exhibited potent anti-inflammatory activity and was sequentially fractioned with molecular weight cut-offs; further active fraction (30- 10 kDa) was purified. The active peak-II was identified as EGLLGDVF (849.435 Da) and exhibited decent functional aspects. The peptide successfully reduced the production of pro-inflammatory cytokines, NO and COX-2 activation; and down-regulated the iNOS and COX-2 protein expression in LPS-stimulated RAW264.7 cells. Conclusion: Our study indicates that EGLLGDVF derived from PVF has potential antiinflammatory applications applicable in food and pharmaceutical industries.

The current objective was framed on isolation of two angiotensin-I converting enzyme inhibitory peptides from coastal trashes of squilla muscle (Harpiosquilla raphidea) prepared by enzymatic hydrolysis using alcalase, thermolysin and trypsin, which showed the highest degree of hydrolysate in 12th h hydrolysate 87.9 ± 1.6%, 63.1 ± 1.1% and 91.1 ± 2.7% respectively. Among these three hydrolysates, alcalase 5th h (64.8 ± 0.3) and thermolysin 6th h (68.4 ± 1.0) found to be maximum ACE-I inhibition activity. Initial separation was performed by ultra filtration (10–3 kDa) into three different fractions, alcalase (below 3 kDa) fraction observed maximum ACE-I inhibition activity with 75.2 ± 3.5% and thermolysin (3–10 kDa) with 79.5 ± 1.0% inhibition. Further, these two fractions have taken to ion exchange and gel filtration chromatography, the identified ACE-I inhibitory fractions (AC-A2 and TH-A2) also examined for its antioxidant properties. Further, these fractions were determined to be non-toxic against cell lines, functional activities by various assays and characterized into tri peptides MSN (Met-Ser-Asn) and MTH (Met-Thr-His) with a molecular weight of 350 Da and 388 Da respectively using LC–MS/MS. These low molecular weight peptides from natural sources may act as potential ingredient for nutraceutical and pharmaceutical industries.

The Meretrix meretrix is abundantly present in the Indian coastal areas which can be used as an important useful bioactive source for industrial applications. The M. meretrix visceral mass (MMV) was hydrolysed with four different enzymes and verified for anti-inflammatory activity with the help of HRBC membrane stabilization (HMS) and albumin denaturation (AD) assay. Among the hydrolysates, the tryptic 6th hour hydrolysate was selected for purification using ultrafiltration and size-exclusion chromatography (SEC). Further, the purified peptide was identified to have six amino acid sequence (HKGQCC, 675.582 Da). However, to confirm the anti-inflammatory effects of the purified peptide, it was investigated for nitric oxide synthase (iNOS), pro-inflammatory cytokines production as well as cyclooxygenase-2 (COX-2) activation in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and also evaluated for its functional properties. The in-vitro gastrointestinal digestion was performed on the peptide which cleaved the peptide into two i.e. MMV1 (HK, 284.1 Da) and MMV2 (GQCC, 410.1 Da). The data suggested that the MMV2 peptide have maximum activity and was found to be stable at high temperatures. The MMV2 peptide demonstrated abrupt localization throughout the adult zebrafish body and successfully downregulated the mRNA levels of inflammation-related genes in LPS-induced adult zebrafish. This study indicates that the peptide MMV2 possesses anti-inflammatory activity by suppressing the induced inflammation and can be a strong competitor against non-steroidal anti-inflammatory drugs (NSAIDs).

Antioxidant peptides protect biological macromolecules against radical damages. The use of these peptides was evaluated using free radicals scavenging assays [2,2-diphenyl-1 picrylhydrazyl (DPPH) and hydroxyl] with the help of UV-visible and electron spin resonance (ESR) spectroscopy methods. The Octopus aegina mantle protein were tested upon hydrolysis using gastrointestinal enzymes up to 12 h, where pepsin hydrolysate exhibited superior properties (DPPH: 44.39±0.67% and hydroxyl: 38.84±1.07%) compared with trypsin and α-chymotrypsin. Consequently, the antioxidant activity of the purified hydrolysate increased on a successive purification, and the peptide sequence was determined to be 368.9 Da with Gly-Glu-Tyr amino acids. Tripeptide exerted free radical scavenging efficiency in DNA damage, lipid peroxidation and cellular destruction (MCF7 cells) under stress condition. The results obtained with octopus antioxidant peptide suggested its role as an adjunct in food and pharmaceutical industries.

The study aimed to identify bioactive peptide from Meretrix meretrix Linnaeus foot (MMF) and examine its potential of suppressing inflammation. In brief, the anti-inflammatory activity was identified by erythrocyte membrane protection and protein denaturation assay from MMF peptic 9th-h hydrolysate and was separated with three molecular weight cut-off units. The obtained four fractions were testified for activity and the fraction (10–3 kDa) with maximum activity was purified using gel permeation chromatography. Finally, the peptide sequence was identified as Asn–Pro–Ala–Gln–Asp–Cys (647.559 Da) by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The hexapeptide was characterised for functional properties at different pH range. The non-toxic hexapeptide was able to reduce the cyclooxygenase (COX)-2 activation, pro-inflammatory cytokines and nitric oxide (NO) production significantly in RAW264.7 macrophage cells. The current results propose that the hexapeptide derived from MMF protein can act as an effective anti-inflammatory against pro-inflammatory cytokines, COX-2 and NO. Moreover, it could be used as an effective alternative source for drugs in pharma and also as an ingredient in food industries.

The visceral mass of the gastropod, Harpa ventricosa was hydrolysed using trypsin, alcalase and pepsin for 12 h to produce protein hydrolysates. Subsequently, the active hydrolysate was observed in the 3rd hour of tryptic hydrolysate (29.17 ± 0.62 and 34.85 ± 0.55 %) using human red blood cell (HRBC) membrane stabilization and albumin denaturation (AD) assays. The active hydrolysate was fractionated by membrane filtration unit, where

The aim was to drive the ACE-I inhibitory peptide from the dumped waste of O. woodmasoni muscle protein hydrolysate after 12 h of hydrolysis using thermolysin and pepsin. The degree of hydrolysis (DH) was observed till 12th hr and the maximum ACE-I inhibition activity was recorded in 2nd and 5th hr (73.51 ± 0.25% & 68.93 ± 0.23%) for thermolysin and pepsin respectively. Further, the higher active thermolysin hydrolysate was separated using ultrafiltration membrane unit and 10-3 kDa fraction showed chief ACE-I inhibition activity (IC50 value: 0.47 mg/mL). The active fraction was purified by consecutive chromatographic techniques using ion exchange chromatography (IEC) & gel filtration chromatography (GFC) using fast protein liquid chromatography (FPLC). Finally, the fraction TH1-A1 evaluated by ACE-I inhibition assay and showed 77.09 ± 2.18% inhibitions. The non-toxic peptide against MCF-7 cells was further characterized for functional properties at pH 2 to 10. The active purified fraction also exhibited antioxidant activity analyzed with various assays and found to have 5 amino acid sequence (Asn-Gly-Val-Ala-Ala) with molecular weight 431 Da through LC-MS/MS. In conclusion, the identified low molecular weight peptide from by catch O. woodmasoni waste has both ACE-I inhibition and antioxidant properties. Therefore, this peptide might be a better alternative nutraceutical and functional food after few more investigations.

Marine organisms provide an intriguing number of bioactive compounds. These bioactive compounds show immunomodulatory, antioxidant, anti-inflammatory and antimicrobial activities. Crabs rank third after shrimps and lobster as seafood delicacies and provide major health benefits when consumed due to presence of proteins, vitamins and unsaturated essential fatty acids. Due to their diverse biological activities, the peptides derived from marine sources may treat various diseases such as migraine, inflammatory bowel disease, rheumatoid arthritis etc. In this study the Crab Leg (CL) muscle was isolated and further hydrolysed using trypsin, alcalase and papain to produce enzymatic hydrolysates. The results obtained from degree of hydrolysis showed that the enzymes significantly cleave the proteins. Furthermore, the HPLC analysis for amino acid compositions of CL showed the sample contained both essential and non-essential amino acids where histidine (%) was highest. In vitro assays for anti-inflammatory activity like Albumin Denaturation (AD) and HRBC Membrane Stabilization (HMS) assay helped to determine the active hour hydrolysate showing the trypsin 3rd hr hydrolysate as having highest activity in CL (90.57 ± 0.95% and 49.94 ± 1.52%). This active hour hydrolysate was purified using gel filtration chromatography and the fractions were determined using AD and HMS assay which resolved fraction Ⅰ to be more active in CL. The low molecular weight peptide sequence was found to be L-G-L-G-A-A-V-L (713.456 Da) by using LC-MS/MS. Further, cell proliferation assay and ELISA were performed for the purified peptide to test the suppression of LPS-mediated induction of COX-2 in RAW264.7 macrophage cells.

In this current investigation, the antioxidant peptides were derived from marine Sepia brevimana mantle by trypsin, α-chymotrypsin and pepsin for 12 h hydrolysis. The active peptides were found in the hydrolysates of trypsin and α-chymotrypsin at the 7th hour and pepsin at the 8th hour. The highest activity was found in trypsin hydrolysate compared to others using various radical scavenging and metal ions transition assays, further the hydrophobic amino acids were observed in more quantity along with other amino acids. Active peptide was purified by consecutive chromatographic techniques and evaluated by DPPH (38.81 ± 1.07%) and reducing power assays (0.478 ± 0.03). The purified peptide exhibited significant inhibition for the linoleic acid auto-oxidation in the model system, protective effect on DNA damage due to hydroxyl radical induction and was non-toxic even at higher concentration. The mass and sequence of the peptide was found to be 679.5 Da and Ile/Leu-Asn-Ile/Leu-Cys-Cys-Asn, respectively. The current results suggested that cuttlefish peptide could be used as natural antioxidant in enhancing antioxidant properties of functional foods and in preventing oxidation reactions in food processing.

Antioxidant peptides were derived from the edible part of Indian squid, Loligo duvauceli, via the use of gastrointestinal enzymes for up to 12 hours. The active α-chymotrypsin hydrolysate exhibited the maximum activity compared to the trypsin and pepsin hydrolysates, as assessed by various radical scavenging and metal chelating assays. Moreover, essential and non-essential amino acids were present in the active hydrolysate. Furthermore, the hydrolysate was purified by ion exchange and gel filtration chromatography using fast protein liquid chromatography (FPLC). The purified peptide exhibited strong free radical scavenging, metal chelation and reducing power abilities that were confirmed with a UV-visible and electron spin resonance (ESR) spectrometer. The peptide also prevented DNA damage and inhibited lipid peroxidation due to its small size (682.5 Da) and content of the high redox potential amino acid sequence Trp-Cys-Thr-Ser-Val-Ser, which was confirmed by ESI-MS/MS. This peptide exhibited no cytotoxic effects on breast cancer cells (MCF7) and scavenged reactive oxygen species at the cellular level under H2O2-induced stress. These results suggest that the peptide derived from squid mantle protein acts as a potent antioxidant against oxidative stress and could be used as an efficient and safer adjunct in food processing.

In the present study, northern whiting fish (Sillago sihama) muscle was hydrolyzed with gastrointestinal enzymes (pepsin, trypsin and α-chymotrypsin) separately and the resulted protein hydrolysates were tested for antioxidant activities using DPPH radical scavenging activity and reducing power assays. The protein hydrolysate obtained from trypsin exhibited highest antioxidant activity. Further, it was fractionated by consecutive chromatography using anion exchange and gel filtration chromatography; the separated fractions were collected and evaluated for antioxidant activity. The results showed that fraction 2 exhibited high chelating activity (73.15 % at 0.5 mg/mL) and best radical scavenging activity for DPPH radical (55.16 % at 0.5 mg/mL), ABTS radical (57.98 % at 50 μg/mL), superoxide radical (39.55 % at 200 μg/mL) and hydroxyl radical (51.33 % at 100 μg/mL). In addition, the active fraction showed strong antioxidant activity in the inhibition of linoleic acid autooxidation (60 % at 0.5 mg/mL) and also it exhibited significant protective effect on DNA damage caused by hydroxyl radicals. The size of the active fraction was found to be

The antioxidant activity of protein hydrolysates prepared from the skin of Sphyraena barracuda (Seela fish) and Lepturacanthus savala (Ribbon fish), using the commercial enzymes pepsin, trypsin, and papain were determined. The protein hydrolysate showed high antioxidant activity in which trypsin hydrolysate of the skin of both seela and ribbon fish proved good DPPH scavenging activity with 66 and 60% (p < 0.05), respectively. These active hydrolysates were purified using fast protein liquid chromatography on ion exchange and gel filtration chromatography procedure and the active purified fractions were determined using electron spin resonance spectrophotometer against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals. Further the purified fractions were analyzed for amino acid composition using high performance liquid chromatography and it consisted of antioxidant inducing amino acids along with a considerable quantity of essential amino acids.

In the present study, bioactive peptide was isolated from protein hydrolysate of Nemipterus japonicus backbone hydrolysed by trypsin. Functional properties like solubility, emulsifying, and foaming capacities of protein hydrolysate were governed by pH. Protein hydrolysate was fractionated by DEAE XK 26/20 anion exchange chromatography followed by G-25 gel filtration chromatography. The fractions collected were tested for radical scavenging properties on DPPH, hydroxyl, and superoxide radicals by electron spin resonance spectrometer. Amino acid composition of a potent fraction was rich in glutamic acid (21.20 g/100 g), lysine (37.50 g/100 g), aspartic acid (5.8 g/100 g), arginine (5.4 g/100 g), and glycine (2.84 g/100 g). Moreover, the potent fraction showed no cytotoxicity on Vero cell lines till 0–100 μg/ml with CC50 = 94 μg/ml, whereas it exerted a significant antitumor property against HepG2 cell line with an IC50 value of 61.1 μg/ml.

Peptide from croaker (Otolithes ruber) muscle protein hydrolysate was purified, characterized and evaluated for its in vitro and in vivo antioxidant activity. Results showed that purified peptide contained the amino acid sequence as Lys-Thr-Phe-Cys-Gly-Arg-His (861.6Da), which were expected to contribute to its antioxidant activities. This peptide efficiently quenched 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals (84.5±1.2 and 62.4±2.9%), and successfully inhibits the lipid peroxidation and DNA damage and proven to be a potent antioxidant at different in vitro systems. It also improved the endogenous cellular antioxidant enzymes in Wistar rat by increasing the activities of catalase (CAT), glutathione-S-transferase (GST) and superoxide dismutase (SOD) after supplementation of the peptide (283.6±7.25, 4.3±0.78 and 28.42±1.97) compared to the negative control (196.4±5.65, 1.3±0.45 and 15.1±0.35). Therefore, croaker muscle peptide can increase an endurance capacity and facilitate recovery from oxidative stress.

Summary To assess the antioxidant properties of fish protein hydrolysate from giant kingfish Caranx ignobilis (Forsskal, 1775), muscle and skin were obtained using various proteases (papain, pepsin, trypsin and α-chymotrypsin), respectively. Antioxidant activities of the resulting hydrolysates were evaluated using 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity, reducing power and metal chelating activity. Among the hydrolysates, peptic of muscle (37 ± 1.0; 0.290 ± 0.012; 63.30 ± 0.57) and tryptic of skin (36.2 ± 1.0; 0.190 ± 0.110; 63 ± 0.57) hydrolysates, which had the highest free radical scavenging activity, was subjected to purification using Sephadex G-25. The fractionated hydrolysates were superior to the original hydrolysates in the antioxidative activity tested. The active fractions (MF2 and SF2) effectively inhibited lipid peroxidation in linoleic acid emulsion system, and the activity was compared with α-tocopherol. The amino acid profile of MF2 and SF2 showed a high level of essential amino acids, and the most abundant amino acids were in the order His (12.01% and 7.08%), Phe (7.05% and 6.18%) and Lys (6.76% and 4.74%). Conclusively, C. ignobilis muscle and skin hydrolysates could be a promising rich source of natural antioxidants.

The current study aims at the isolation and characterization of the peptides, believed to have antioxidant activity, from Conus betulinus by using different types of enzymes. The body and viscera of C. betulinus were treated with three enzymes viz. trypsin, pepsin and papain to obtain peptide hydrolysates. The activities of the hydrolysates were analyzed by DPPH and hydroxyl radical assay by using electron spin resonance (ESR) device. Active hydrolysates were purified using ion exchange chromatography followed by gel filtration chromatography. The activity of the separated fractions was analyzed by ESR; in which the result showed that trypsin hydrolysate of body (28.48 and 76.00%) and viscera (38.45 and 83.00%) respectively have high activity than the other hydrolysates. The HPLC result of purified fraction showed, presence of active amino acids viz., metheonine, cystine, histidine etc. This purified peptide has more antioxidant activity that could reduce the excess free radicals in body in order to prevent free radical induced diseases.

We have investigated the antioxidant activity of protein hydrolysates prepared from backbones of two commercially important fishes; seela (Sphyraena barracuda) and ribbon fish (Lepturacanthus savala). Pepsin and trypsin hydrolysates were found more potent to inhibit lipid peroxidation in case of ribbon and seela fish respectively and were further purified by using fast protein liquid chromatography on anion exchange and gel filtration chromatography. The active peaks after gel filtration chromatography of seela fish was able to scavenge 2,2-diphenyl-1-picryhydrazyl and hydroxyl radicals by 61 ± 2.3 and 58.7 ± 2.3% and ribbon fish hydrolysate by 60.0 ± 2.6 and 55.6 ± 1.8% as measured by ESR spectroscopy. And the active fractions showed presence of both essential and non-essential amino acids with high percentages of arginine (11.95 and 12.76%) and lysine (13.49 and 13.89%).

In the present study, a peptide having high antioxidant properties was isolated from horse mackerel viscera protein, Magalaspis cordyla . In vitro gastrointestinal digestion was employed to obtain potential protein hydrolysate and was subjected to consecutive chromatographic methods using fast protein liquid chromatography (FPLC) connected to diethyl amino ethyl (DEAE) anion exchange column and Sephadex G-25 gel filtration column. The activity of the fractions was tested against DPPH and hydroxyl radicals and the isolated peptide showed 89.2 and 59.1 percentage of scavenging. The amino acid sequence of purified peptide was determined using ESI-MS/MS as Ala–Cys–Phe–Leu (518.5 Da), it exhibited high activity against polyunsaturated fatty acid (PUFA) peroxidation than that of natural antioxidant, α-tocopherol.

The antioxidant activity of marine clam, Meretrix casta (Chemnitz) protein hydrolysates prepared from different organs (body, foot and viscera), using the commercial enzymes (pepsin, trypsin and papain) were determined. The protein hydrolysate had a high antioxidant activity where, pepsin hydrolysate of viscera and trypsin hydrolysate of body and foot showed good activity. The viscera pepsin hydrolysate and foot trypsin hydrolysates were purified using FPLC on ion exchange and gel filtration chromatography procedure and activity was determined by DPPH radical scavenging and reducing ability assays. Further the amino acid content of the purified fractions was analyzed using HPLC. Active fractions contained good quantity of both essential and non-essential amino acids.

Summary The aim of this study was to evaluate antioxidant, antiproliferative and antimicrobial properties of flying fish (Exocoetus volitans) backbone hydrolysed by three different enzymes namely papain, pepsin and trypsin. The in vitro antioxidant potencies of hydrolysates and purified peptides against 1, 1-diphenyl-2-picrylhydrazyl, superoxide and hydroxyl radicals were evaluated by electron spin resonance spectroscopy. The peptic protein hydrolysate showed maximum free radical scavenging potential and lipid peroxidation inhibition and was further purified by DEAE XK 26/20 anion exchange chromatography followed by G-25 gel permeation chromatography. The amino acid composition of potent purified fraction was determined by HPLC, contains essential and nonessential amino acids with glutamic acid (24.10%), lysine (23.62%), glycine (12.05%) and threonine (10.41%) as the dominant amino acids. The potent purified fraction was tested for cell cytotoxicity on Vero and Hep G2 cell lines. It was found that fraction IIIb did not show any cytotoxic effect for Vero cell lines and exerted a significant antiproliferative effect on Hep G2 cell lines.

The focus of the study was to investigate the antioxidant activity of hydrolyzed muscle protein of Nemipterus japonicus and Exocoetus volitans. The trypsin protein hydrolysates of both fish showed maximum free radical scavenging potential and lipid peroxidation inhibition. Furthermore, it was purified by chromatographic methods followed by the lipid peroxidation inhibition; free radical scavenging assay was performed before and after purification. The purified peptide fractions of N. japonicus and E. volitans exhibited higher activity against polyunsaturated fatty acids (PUFA) peroxidation which was similar to natural antioxidants like α-tocopherol. Free radical scavenging potencies were measured by electron spin resonance technique (ESR). The purified peptide of E. volitans quenched free radicals (DPPH, hydroxyl, and superoxide) slightly more than N. japonicus. The amino acid composition of both fish protein hydrolysates showed variations in their ratio. The purified peptides were tested for cell cytotox...

Body, foot and viscera of Donax cuneatus (Linnaeus) were hydrolyzed using commercial proteases (pepsin, trypsin and papain) and tested for their antioxidant activity by DPPH scavenging ability and reducing power assays. In comparison between all the hydrolysates, papain viscera (28.513 ± 0.165 & 0.186 ± 0.008) and foot (33.567 ± 0.132 & 0.166 ± 0.013) hydrolysates showed highest DPPH and reducing power ability respectively. The active hydrolysates were purified with DEAE- cellulose followed by Sephadex G-25 columns connected to FPLC. Further, the isolated active fractions were loaded onto HPLC for their amino acid profiling and found with the presence of potential amino acids viz., histidine, cysteine, alanine etc. These results suggest that the isolated antioxidant peptide from viscera and foot hydrolysate of D. cuneatus can be used in treating human diseases where free radicals and oxidative damage are involved.

Functional properties and antioxidant activity of pink perch (Nemipterus japonicus) muscle hydrolysed by three different enzymes papain, pepsin and trypsin were studied. The protein hydrolysates produced by trypsin had an excellent solubility (98%) compared to pepsin (77%) and papain hydrolysate (74%). Conversely, the emulsifying activity index (ESI) and foaming abilities were affected by pH. DPPH radical scavenging ability, reducing power and metal chelating activity of protein hydrolysates increased with increase in concentration. Lipid peroxidation was strongly inhibited by 64% by protein hydrolysates produced by trypsin. The results revealed that the functional properties and antioxidant activities of pink perch were greatly affected by the enzymes used.

In the current study, two peptides with antioxidant properties were purified from skin protein hydrolysates of horse mackerel (Magalaspis cordyla) and croaker (Otolithes ruber) by consecutive chromatographic fractionations including ion exchange chromatography and gel filtration chromatography. By electron spray ionization double mass spectrometry (ESI-MS/MS), the sequence of the peptide from the skin protein hydrolysate of horse mackerel was identified to be Asn-His-Arg-Tyr-Asp-Arg (856 Da) and that of croaker to be Gly-Asn-Arg-Gly-Phe-Ala-Cys-Arg-His-Ala (1101.5 Da). The antioxidant activity of these peptides was tested by electron spin resonance (ESR) spectrometry using 1-diphenyl-2-picryl hydrazyl (DPPH·) and hydroxyl (OH·) radical scavenging assays. Both peptides exhibited higher activity against polyunsaturated fatty acid (PUFA) peroxidation than the natural antioxidant α-tocopherol. These results suggest that the two peptides isolated from the skin protein hydrolysates of horse mackerel and croaker are potent antioxidants and may be effectively used as food additives and as pharmaceutical agents.