Antioxidant properties of peptide fractions from silver carp (Hypophthalmichthys molitrix) processing by-product protein hydrolysates evaluated by electron spin resonance spectrometry

Characterization of selenium-containing broccoli (Brassica oleracea L. var. italica planch) proteins and evaluation of antioxidant activity by electron spin resonance

Selenoproteins found in selenium (Se)-enriched vegetables play a vital role in maintaining human health. In this study, four Se-containing broccoli proteins (Se-BP: albumin, globulin, prolamin, and glutelin) were continuous extracted by Osborne method. Three ultrafiltered fractions were subsequently obtained from the glutelin hydrolysate, composed of Se-contained broccoli peptides (Se-Bp) with different molecular weights (MW), namely, < 1 kDa, 1-3 kDa, and 3-10 kDa. Glutelin exhibited the highest protein yield (65.60 ± 1.07%), purity (78.39 ± 0.95%), nutritional value, organic Se content (88.05 ± 0.32% of total Se content), and Se speciation distribution (selenocystine, selenomethionine, methylselenocysteine, and selenoethionine). Additionally, the antioxidant activity of different MW of Se-Bp was assessed using electron spin resonance spectroscopy. The results revealed that antioxidant activity of the candidate peptide is dependent upon its Se content, amino acid composition, and MW, especially Se-Bp with MW of 1-3 kDa displayed the strongest free radical scavenging ability.

Sea Bass Side Streams Extracts Obtained by Pulsed Electric Fields: Nutritional Characterization and Effect on SH-SY5Y Cells

Fish side streams are an environmental and economic problem. In this work, pulsed electric fields (PEF) extraction was optimized and used as a new method for their valorization. Sea bass head, skin, viscera, and backbone were used. PEF technology (123-300 kJ/kg, 1-3 kV/cm) improved the extraction of proteins and antioxidant compounds from head and skin, but was not successful for viscera. SDS-PAGE showed that the protein molecular weight distribution was affected by the extraction process, revealing differences between the control and PEF extraction conditions. In addition, the extraction of macro-minerals and micro-minerals were also evaluated. The effect of PEF differed according to the matrix and the mineral studied. Heavy metals were also taken into account, studying the presence of As, Cd, Hg, and Pb in the extracts. PEF pre-treatment reduced the presence of As in skin, viscera, and backbone, ranging from 18.25 to 28.48% according to the matrix evaluated. The analysis of potential antioxidant bioactive peptides showed that the treatment of the sample directly influenced their variety. Additionally, the extracts obtained from the head were found to increase cell viability when tested on SH-SY5Y cells. In conclusion, PEF extraction can be a useful tool for the valorization of fish side streams.

Impacts of pH and Base Substitution during Deaerator Treatments of Herring Milt Hydrolysate on the Odorous Content and the Antioxidant Activity

Despite the biological interest in herring milt hydrolysate (HMH), its valorization is limited by its unpleasant odor resulting from the presence of mainly amine and carbonyl compounds. Recently, a deaerator was demonstrated as an interesting avenue to reduce the odorous content of HMH. However, the removal rate of amine and carbonyl compounds was highly dependent on the operating conditions, and the impact of such a process on the biological potential of HMH was not considered. Therefore, this study aimed to optimize the deaerator process by assessing the impacts of the combination of deaerator treatments at neutral and basic pH, the increase in pH from 10 to 11, and the substitution of NaOH by KOH on the odorous content and the antioxidant activity of HMH. Results showed that the highest deodorization rate of HMH was obtained when a deaerator treatment at neutral pH was combined with another one at basic pH using KOH for alkalization. This condition resulted in a decrease in the dimethylamine and trimethylamine contents by 70%, while certain compounds such as 2,3-pentanedione, methional, (E,E)-2,4-heptadienal, or (E,Z)-2,6-nonadienal were almost completely removed. Removal mechanisms of the targeted compounds were totally identified, and the performance of the developed process was confirmed by sensory analysis. Lastly, it was shown that the antioxidant potential of HMH was not affected by the deodorization process. These results demonstrated the feasibility of deodorizing a complex matrix without affecting its biological potential.

Cytoprotective Effects of Fish Protein Hydrolysates against H2O2-Induced Oxidative Stress and Mycotoxins in Caco-2/TC7 Cells

Many studies report the potent antioxidant capacity for fish protein hydrolysates, including radical scavenging activity and inhibition ability on lipid peroxidation (LPO). In this study, the in vitro cytotoxicity of protein hydrolysates from different salmon, mackerel, and herring side streams fractions was evaluated in the concentration range from 1 to 1:32 dilution, using cloned human colon adenocarcinoma cells TC7 (Caco-2/TC7) by MTT and PT assays. The protein hydrolysates' antioxidant capacity and oxidative stress effects were evaluated by LPO and reactive oxygen species (ROS) generation, respectively. The antioxidant capacity for pure and bioavailable hydrolysate fraction was also evaluated and compared. Additionally, mycotoxin levels were determined in the fish protein hydrolysates, and their cytoprotective effect against T-2 toxin was evaluated. Both hydrolysates and their bioavailable fraction induced similar cell viability rates. The highest cytoprotective effect was obtained for the salmon viscera protein hydrolysate (HSV), which increased the cell viability by 51.2%. ROS accumulation induced by H₂O₂ and LPO was suppressed by all pure hydrolysates. The cytoprotective effect of hydrolysates was observed against T-2. Moreover, the different fish fraction protein hydrolysates contain variable nutrients and unique bioactive peptide composition showing variable bioactivity, which could be a useful tool in developing dietary supplements with different target functional properties.

Evaluating the Effects of MKAVCFSL Derived from Bighead Carp (Hypophthalmichthys nobilis) Flesh on Antioxidant Activity in Caco-2 Cells In Vitro

The effect of an antioxidative peptide Met-Lys-Ala-Val-Cys-Phe-Ser-Leu (MKAVCFSL) on oxidative stress in Caco-2 cell lines was investigated. Caco-2 cells exposed to excess oxidative stress could be restored when pretreated with the peptide. Reactive oxygen species (ROS) and malondialdehyde (MDA) within the cells could be scavenged by MKAVCFSL. The peptide could also enhance the activity of glutathione peroxidase (GPx), glutathione reductase (GR), and superoxide dismutase (SOD), while catalase (CAT) activity did not show a significant difference between treatment and control samples. Meanwhile, it was observed that peptide treatment increased the concentration of glutathione (GSH). Yet the content of glutathione disulfide (GSSG) was hardly affected. The stability of MKAVCFSL was also assessed and an intact peptide was observed after simulated gastrointestinal digestion. Part of the peptide was hydrolyzed into fragments including MKA, FSL, AVCFSL, and MKAVCF. This study demonstrated that MKAVCFSL derived from bighead carp hydrolysates could ameliorate oxidative stress to protect the Caco-2 cells.

Fractionation of Protein Hydrolysates of Fish Waste Using Membrane Ultrafiltration: Investigation of Antibacterial and Antioxidant Activities

In this study, yellowfin tuna (Thunnus albacores) viscera were hydrolyzed with protamex to obtain hydrolysate that is separated by a membrane ultrafiltration into four molecular size fractions (< 3, 3-10, 10-30, and 30 kDa <). Antibacterial and antioxidant properties of the resulting hydrolysates and membrane fractions were characterized, and results showed that the lowermost molecular weight fraction (< 3 kDa) had significantly the highest (P < 0.05) percentage of bacteria inhibition against Gram-positive (Listeria and Staphylococcus) and Gram-negative (E. coli and Pseudomonas) pathogenic and fish spoilage-associated microorganisms and scavenging activity against DPPH and ABTS radical and ferric reducing antioxidant power among the fractionated enzymatic hydrolysates. These results suggest that the protein hydrolysate derived from yellowfin tuna by-products and its peptide fractions could be used as an antimicrobial and antioxidant ingredient in both nutraceutical applications and functional food.

Ultrasound treatment on the structure of goose liver proteins and antioxidant activities of its enzymatic hydrolysate

This study was to investigate the effects of ultrasonic treatment on the physical and chemical properties of goose liver protein (GLP) and the anti-oxidative activity of the goose liver protein hydrolysate (GLPH). By measuring the average particle size, sulfhydryl and disulfide bond, secondary structure, hydroxyl radical inhibition, 1, 1-diphenyl-2-picrylhydrazyl radical scavenging rate, and ferrous ion chelating ability, we found that 300 and 600 W ultrasonic treatment reduced the particle size of GLP from 509.7 μm to 313.7 μm and 273.1 μm, respectively, and significantly decreased the content of sulfhydryl and the structures of α-helix and β-turn (p < .05). Meanwhile, the content of disulfide bond and β-sheet structure increased significantly (p < .05); the antioxidant capacity of GLPH increased significantly (p < .05). After 300 W ultrasonic treatment, the GLP in the enzymatic hydrolysis process was more conducive to the release of antioxidant substances compared with the 600 W ultrasonic-treated GLP. PRACTICAL APPLICATIONS: The physical and chemical properties of the GLP were changed by ultrasonic treatment, which was beneficial to improve the texture quality of goose liver paste and the anti-oxidative activity of GLPH. It could enhanced the functional characteristics of goose liver paste by enzymolysis. Meanwhile, antioxidant components extracted by ultrasonic treatment from goose liver could be added to foods as an excipient to improve the antioxidant properties.

In-vitro antioxidant capacity and cytoprotective/cytotoxic effects upon Caco-2 cells of red tilapia (Oreochromis spp.) viscera hydrolysates

The antioxidant capacity of red tilapia viscera hydrolysates (RTVH) with different degrees of hydrolysis (DH) as well as their ultrafiltration membrane fractions, were analyzed using different chemical assays. Their protective effects against oxidative stress were evaluated using H₂O₂-stressed human intestinal differentiated Caco-2. The highest antioxidant capacity was obtained with a DH of 42.5% (RTVH-A) and its <1 kDa fraction (FRTVH-V). RTVH-A and FRTVH-V did not show cytotoxic effects at a concentration of ≤0.5 mg/mL,prevented the decrease in cell viability, and suppressed intracellular reactive oxygen species (ROS) accumulation induced by H₂O₂. However, pretreatment with RTVH-A after adding H₂O₂, showed a greater decrease in glutathione levels. Moreover, FRTVH-V allowed for a recovery close to that of control levels of cell proportions in the G1 and G2/M cell cycle phases; and a decrease in the cell proportion in late apoptosis. These results suggest that RTVH-A and FRTVH-V can be beneficial ingredients with antioxidant properties and can have protective effects against ROS-mediated intestinal injuries.

Molecular modification, expression and purification of new subtype antioxidant peptide from Pinctada fucata by recombinant Escherichia coli to improve antioxidant-activity

The aim of this study was to establish a system for the efficient expression and purification of new subtype of antioxidant peptide from Pinctada fucata meat (NPFMAP), which is designed by molecular modification technology based on the sequence of purified and identified antioxidant peptide from Pinctada fucata meat (PFMAP, Gly-Ala-Gly-Leu-Pro-Gly-Lys-Arg-Glu-Arg), and to better understand the relationship between structure and antioxidant activity. Meanwhile, gene codon usage was optimized and the glutathione S-transferase (GST) tag of pGEX-6P-1 was added to facilitate expression and purification NPFMAP in Escherichia coli. The results of antioxidant activity assay in vitro showed a higher antioxidant activity in NPFMAP than that in enzymatic hydrolysis digested or chemically synthesized PFMAP. In particular, the DPPH scavenging radical activity increased by about 4.7 times after molecular modification. Structural bioanalysis indicated that new subtype antioxidant peptide had spatial conformation and good hydrophilic after modification, which was confirmed by antioxidant activity assays. Thus, the proposed method could be used to obtain NPFMAP with high antioxidant activity.

Purification and Characterization of an Antioxidant Protein from Fertilized Eggs

Free radicals may attack cells or tissue, leading to chronic diseases, and antioxidant consumption is potentially useful for removing free radicals. Egg proteins may be used as potential sources of antioxidant considering their ability of scavenging free radicals to apply for food or cosmetics industry. In this study, we obtained a natural antioxidant protein from fertilized eggs, which was a dietary supplement in some Asian countries. Meanwhile, antioxidant activities of these proteins were evaluated using different oxidation systems. With increasing incubation time, the antioxidant activity of these proteins increased during 15 d of incubation. The samples on day 15 were performed for isolation of antioxidant protein. The protein, named P4-1 (MW, 45 kDa), was isolated and purified by consecutive chromatographic methods. P4-1 contained 17 amino acids, which was determined by liquid chromatography-mass spectrometry and Amino Acid Analyzer. Moreover, the amino acid sequence was highly similar to that of ovalbumin. Differential scanning calorimetry showed that the denaturation temperature of P4-1 was 57.16℃. Furthermore, P4-1 suggested high oxygen radical-absorbance activity in ·OH assays, and its antioxidant activity was stable at 30-50℃ in acidic and neutral pH. Thus, these results revealed that P4-1 may be a potential resource as a natural antioxidant.

A Review of the Latest Advances in Encrypted Bioactive Peptides from Protein-Rich Waste

Bioactive peptides are considered the new generation of biologically active regulators that not only prevent the mechanism of oxidation and microbial degradation in foods but also enhanced the treatment of various diseases and disorders, thus increasing quality of life. This review article emphasizes recent advances in bioactive peptide technology, such as: (i) new strategies for transforming bioactive peptides from residual waste into added-value products; (ii) nanotechnology for the encapsulation, protection and release of controlled peptides; and (iii) use of techniques of large-scale recovery and purification of peptides aiming at future applications to pharmaceutical and food industries.

Amaranth peptides from simulated gastrointestinal digestion: antioxidant activity against reactive species

We evaluated the capacity of simulated gastrointestinal digests or alcalase hydrolysates of protein isolates from amaranth to scavenge diverse physiologically relevant reactive species. The more active hydrolysate was obtained with the former method. Moreover, a prior alcalase treatment of the isolate followed by the same simulated gastrointestinal digestion did not improve the antioxidant capacity in any of the assays performed and even produced a negative effect under some conditions. Gastrointestinal digestion produced a strong increment in the scavenging capacity against peroxyl radicals (ORAC assay), hydroxyl radicals (ESR-OH assay), and peroxynitrites; thus decreasing the IC50 values to approximately 20, 25, and 20%, respectively, of the levels attained with the nonhydrolyzed proteins. Metal chelation (HORAC assay) also enhanced respect to isolate levels, but to a lesser extent (decreasing IC50 values to only 50%). The nitric-oxide- and superoxide-scavenging capacities of the digests were not relevant with respect to the methodologies used. The gastrointestinal digests from amaranth proteins acted against reactive species by different mechanisms, thus indicating the protein isolate to be a potential polyfunctional antioxidant ingredient.

Isolation and characterisation of in vitro and cellular free radical scavenging peptides from corn peptide fractions

Corn gluten meal, a corn processing industry by-product, is a good source for the preparation of bioactive peptides due to its special amino acid composition. In the present study, the in vitro and cellular free radical scavenging activities of corn peptide fractions (CPFs) were investigated. Results indicated that CPF1 (molecular weight less than 1 kDa) and CPF2 (molecular weight between 1 and 3 kDa) exhibited good hydroxyl radical, superoxide anion radical and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonicacid) diammonium salt (ABTS) radical scavenging activity and oxygen radical absorbance capacity (ORAC). Meanwhile, the in vitro radical scavenging activity of CPF1 was slightly higher than that of CPF2. Both CPF1 and CPF2 also exhibited significant cytoprotective effects and intracellular reactive oxygen species scavenging activity in Caco-2 cells exposed to hydrogen peroxide (H2O2). The amino acid composition analysis revealed that the CPF were rich in hydrophobic amino acids, which comprised of more than 45% of total amino acids. An antioxidant peptide sequence of Tyr-Phe-Cys-Leu-Thr (YFCLT) was identified from CPF1 using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI TOF/TOF MS). The YFCLT exhibited excellent ABTS radical scavenging activity with a 50% effective concentration (EC50) value of 37.63 µM, which was much lower than that of Trolox. In conclusion, corn gluten meal might be a good source to prepare antioxidant peptides.

Antioxidant activity and functional properties of enzymatic protein hydrolysates from common carp (Cyprinus carpio) roe (egg)

Previously, we have reported the composition, molecular mass distribution and in vivo immunomodulatory effects of common carp roe protein hydrolysates. In the current study, antioxidative activity and functional properties of common carp (Cyprinus carpio) roe (egg) protein hydrolysates, prepared by pepsin, trypsin and Alcalase, were evaluated. The three hydrolysates showed excellent antioxidant activities in a dose dependent manner in various in vitro models such as 2,2 diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2'-azino-bis(3-ethylbenzthiazoline-6)-sulfonic acid (ABTS(+)) radical scavenging activity, ferric reducing antioxidant power (FRAP) and ferrous ion (Fe(2+)) chelating ability. Enzymatic hydrolysis significantly increased protein solubility of the hydrolysates to above 62 % over a wide pH range (2-12). Carp roe hydrolysates exhibited good foaming and emulsification properties. The results suggest that bioactive carp roe protein hydrolysates (CRPHs) with good functional properties could be useful in health food/nutraceutical/pharmaceutical industry for various applications.

Ex vivo digestion of carp muscle tissue – ACE inhibitory and antioxidant activities of the obtained hydrolysates

This paper reports that carp muscle tissue hydrolysates obtained after ex vivo digestion show the ACE inhibitory and antioxidative activities.

Fractionation, physicochemical properties, nutritional value, antioxidant activity and ACE inhibition of palm kernel expeller protein

This paper provides valuable information on the nutritional quality, functional properties, antioxidative and ACE inhibition of palm kernel expeller protein fractions.

Preparation and Characterization of Antioxidant Peptides from Fermented Goat Placenta

The goat placenta was fermented by Bacillus subtilis and the optimal fermentation parameters of strongest antioxidant capacity of peptides were obtained using response surface methodology (RSM). The effects of fermentation time, initial pH value and glucose content on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity of the goat peptides were well fitted to a quadric equation with high determination coefficients. According to the data analysis of design expert, the strongest DPPH radical scavenging capacity value was obtained with the following conditions: content of glucose was 2.23%, initial pH value was 7.00 and fermentation time was 32.15 h. The DPPH radical scavenging capacity commonly referring antioxidant activity showed a concentration dependency and increased with increasing peptide concentration. The effects of temperature and pH were assessed to determine the stability of antioxidant peptides prepared from goat placenta. Antioxidant peptides showed good stabilities when temperature was lower than 70℃. However, the antioxidant peptides lost antioxidant activities rapidly under alkaline and excessive acid condition. Ultrafiltration technique was performed to separate fermentation broth with different Mw (molecular weight). It was found that peptides in the range of < 3 KDa mainly accounted for the antioxidant activities.

Application and bioactive properties of proteins and peptides derived from hen eggs: opportunities and challenges

Several proteins and peptides that are released in vitro and/or in vivo from hen eggs are biologically active and have a variety of functional properties in humans beyond normal nutrition, for which extensive studies have been performed. This review focuses on their biological activities, including antihypertensive, antioxidant, antimicrobial, antiadhesive, immunomodulatory and antithrombotic activities and enhancement of mineral absorption. These proteins and peptides have been shown to regulate the nervous system, cardiovascular system, immune system and gastrointestinal system. The potential application and future directions of research on these bioactive peptides and proteins in the food industry are also addressed.

DPPH radical scavenging activity of a mixture of fatty acids and peptide-containing compounds in a protein hydrolysate of Jatropha curcas seed cake

Jatropha curcas, a tropical plant, has great potential commercial relevance as its seeds have high oil content. The seeds can be processed into high-quality biofuel producing seed cake as a byproduct. The seed cake, however, has not gotten much attention toward its potential usefulness. This work was aimed to determine the antioxidant activity of different fractions of a protein hydrolysate from J. curcas seed cake and to elucidate the molecular structures of the antioxidants. Seed cake was first processed into crude protein isolate and the protein was hydrolyzed by Neutrase. The hydrolysate obtained from 1 h of Neutrase hydrolysis showed the strongest antioxidant activity against DPPH radical (2,2-diphenyl-1-picrylhydrazyl). After a purification series of protein hydrolysate by liquid chromatography, chemicals acting as DPPH radical inhibitors were found to be a mixture of fatty acids, fatty acid derivatives, and a small amount of peptides characterized by mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy.

Free radical scavenging activity of peptide fractions from defatted soybean meal hydrolysates evaluated by electron spin resonance

Defatted soybean meal, a by-product of soybean oil extraction, was pretreated by ultrasonic and hydrolyzed with neutrase. The DSMH pretreated at 400 W of ultrasonic power, identified to possess the strongest antioxidant activity, was fractionated according to molecular weight into three fractions of DSMH-I (>10 kDa), DSMH-II (5-10 kDa), and DSMH-III (<5 kDa) using ultrafiltration. The fraction, DSMH-III (<5 kDa), exhibited the highest antioxidative activity and was further purified using ion-exchange chromatography. The DSMH-III was separated into five fractions (A, B, C, D, and E). Fraction C with molecular weight of 2434 Da exhibited the strongest free radical scavenging, which was evidenced by the electron spin resonance of 1,1-diphenyl-2-pycryl hydrazyl and hydroxyl radicals. Fraction C was subjected to reverse-phase high performance liquid chromatography and the sequences of the highest activity peptide were determined by liquid chromatography tandem mass spectrometry. The strongest antioxidant activity peptide had the amino acid sequence of Glu-Glu-Gln-Glu-Trp-Pro-Arg-Lys-Glu-Glu-Lys. In conclusion, ultrasonic treatment and ultrafiltration could enhanced antioxidant activity of DSMH.

Optimisation of antioxidant peptide preparation from corn gluten meal

BACKGROUND

Corn gluten meal, containing approximately 600 g kg(-1) protein, is a main by-product of corn wet milling. The annual output of corn gluten meal in China is over 840 000 tons. However, it is difficult to utilise corn gluten meal in the food industry because of its low water solubility and amino acid imbalance. In the present study, corn gluten meal was hydrolysed by different proteases to produce hydrolysates with antioxidant activity in order to increase its value. The hydrolysis conditions were optimised by multiple linear regression and response surface methodology. Furthermore, the amino acid sequence of one corn peptide was determined.

RESULTS

The optimal conditions for alkaline protease hydrolysis were a pH of 9.5, an enzyme/substrate (E/S) ratio of 8 g per 100 g, a liquid/solid ratio of 25 mL g(-1) and a time of 75 min, while the optimal conditions for flavourzyme hydrolysis were a pH of 7, an E/S ratio of 4.2 g per 100 g and a time of 66 min. After gel filtration chromatography, fraction F2 exhibited the highest antioxidant activities. The amino acid sequence of a purified peptide in fraction F2 was determined as Gly-His-Lys-Pro-Ser (507.2 Da).

CONCLUSION

The results indicate that corn gluten meal hydrolysates and/or its isolated peptides are potent antioxidants.

Comparative Study on Biochemical Properties and Antioxidative Activity of Cuttlefish (Sepia officinalis) Protein Hydrolysates Produced by Alcalase and Bacillus licheniformis NH1 Proteases

Antioxidative activities and biochemical properties of protein hydrolysates prepared from cuttlefish (Sepia officinalis) using Alcalase 2.4 L and Bacillus licheniformis NH1 proteases with different degrees of hydrolysis (DH) were determined. For the biochemical properties, hydrolysis by both enzymes increased protein solubility to above 75% over a wide pH range. The antioxidant activities of cuttlefish protein hydrolysates (CPHs) increase with increasing DH. In addition, all CPHs exhibited antioxidative activity in a concentration-dependent manner. NH1-CPHs generally showed greater antioxidative activity than Alcalase protein hydrolysates (P < 0.05) as indicated by the higher 1,1-diphenyl-1-picryhydrazyl (DPPH) radical scavenging activity and ferrous chelating activity. Both Alcalase and NH1 protein hydrolysates were able to retard lipid peroxidation and β-carotene-linoleic acid oxidation. Alcalase-CPH (DH = 12.5%) and NH1-CPH (DH = 15%) contained 75.36% and 80.11% protein, respectively, with histidine and arginine as the major amino acids, followed by glutamic acid/glutamine, serine, lysine, and leucine. In addition, CPHs have a high percentage of essential amino acids made up 48.85% and 50.04%. Cuttlefish muscle protein hydrolysates had a high nutritional value and could be used as supplement to poorly balanced dietary proteins.