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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.

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.

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.

Acid and pepsin-soluble collagen was isolated from the skin of horse mackerel (Magalaspis cordyla) and croaker (Otolithes ruber) using 0.5 M acetic acid followed by precipitation with 0.9 M NaCl. The yields of acid soluble collagen were 17.3 ± 0.4 and 21.9 ± 0.6% and pepsin soluble collagen (22.5 ± 0.8 and 25.7 ± 0.3%) as per wet weight basis, respectively. The extracted acid soluble collagen and pepsin soluble collagen were characterized by SDS-PAGE, amino acid composition and FTIR spectroscopy. SDS-PAGE showed that all the extracted collagen contained two alpha components (α 1 and α 2) and one beta component (β); all the collagens were typical type I and maintained their triple helical structures well with slight molecular structure differences. The amino acid profiles of these collagens were similar with a low imino acid content. Therefore, there is a possibility to use horse mackerel and croaker skin collagen as an alternative source for commercial collagen and may find applications in the food, cosme...

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.

Objective To determine the proximate and fatty acid composition of muscle, viscera, skin and bone of marine fish's horse mackerel and croaker. Methods Freshly collected fishes were dissected and their moisture, ash and protein content were estimated gravimetrically by AOAC procedure and the lipid was extracted using chloroform, methanol and water in a ratio proposed by Bligh and Dyer. Extracted lipid was injected into gas chromatography connected to BPX-70 glass column to evaluate the fatty acid composition. Results All the body parts analyzed had varying moisture content in between 73%–83%. Horse mackerel contained less than 3% and croaker had above 4% of lipid in all the body parts except muscle (1.4%). Fatty acid and lipid class composition was determined for all the body parts and the dominant polyunsaturated fatty acids (PUFA) was docosahexaenoic acid (DHA). Conclusion Both the fish species showed variation, in protein content, lipid content and fatty acid composition. However, croaker had more remarkable quantity of lipid than horse mackerel.

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.

To make more effective use of available marine resources, acid soluble collagen (ASC) was isolated from body and foot of wedge clam Donax cuneatus Linnaeus, 1758 with acetic acid and was characterized for their potential and commercial applications. The yield of ASC was 17% and 23% respectively. SDS PAGE, UV and FTIR spectroscopy showed that both were type I mainly with slight differences. HPLC was used for identifying the presence of different types of amino acids, where glycine was more or less 20% in both the samples and takes the lead amino acid position and presence of imino acids (11.8 and 12.6%) has been the characteristic feature of type I collagen.

Summary In our present investigation, Nemipterus japonicus and Exocoetus volitans backbone protein were hydrolysed by proteases like trypsin and pepsin, respectively. The protein hydrolysates were purified by different chromatographic methods, and the resulted purified peptides were analysed for their amino acid sequences by electrospray ionisation–MS/MS. The analysis of peptides showed sequences as Gly-His-Met-Ser (451.8 Da) and Leu-Glu-Val-Lys-Pro (596.9 Da) for N. japonicus and E. volitans muscle, respectively. The presence of hydrophobic amino acids contributes more to the antioxidant activities of peptides than other amino acids. Moreover, sequence of amino acids in peptides plays an important role in their antioxidant activities.

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.

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.

In the present study, protein of muscles of commercially important marine fishes Nemipterus japonicus and Exocoetus volitans were extracted by trypsin and their hydrolysis conditions viz., temperature, time, and enzyme to substrate concentration on degree of hydrolysis were studied by response surface methodology. The optimum values for N. japonicus was found as temperature, 30°C, hydrolysis time of 100 min an enzyme/substrate concentration of 1.59% whereas, for E. volitans muscle protein, optimum hydrolysis conditions were temperature, 30°C, hydrolysis time of 115 min and enzyme/substrate concentration of 1.67%. Furthermore, amino acid sequence of antioxidant peptides derived after chromatographic purification was identified by ESI–MS/MS. The analysis of peptides showed sequences as Glu-Ser-Asp-Arg-Pro (620.3 Da) and Gly-Trp-Met-Gly-Cys-Trp (747.3) for N. japonicus and E. volitans muscle, respectively. The peptides contained important antioxidant amino acids and acted as good antioxidant peptides to scavenge free radicals.

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.