Purification and characterization of novel antioxidant peptides from enzymatic hydrolysates of tilapia (Oreochromis niloticus) skin gelatin

Research progress of fishy odor in aquatic products: From substance identification, formation mechanism, to elimination pathway

Fishy odor in aquatic products has a significant impact on the purchasing decisions of consumers. The production of aquatic products is a complex process involving culture, processing, transportation, and storage, which contribute to decreases in flavor and quality. This review systematically summarizes the fishy odor composition, identification methods, generation mechanism, and elimination methods of fishy odor compounds from their origin and formation to their elimination. Fishy odor compounds include aldehydes (hexanal, heptanal, and nonanal), alcohols (1-octen-3-ol), sulfur-containing compounds (dimethyl sulfide), and amines (trimethylamine). The mechanism of action of various factors affecting fishy odor is revealed, including environmental factors, enzymatic reactions, lipid oxidation, protein degradation, and microbial metabolism. Furthermore, the control and removal of fishy odor are briefly summarized and discussed, including masking, elimination, and conversion. This study provides a theoretical basis from source to elimination for achieving targeted regulation of the flavor of aquatic products, promoting industrial innovation and upgrading.

Antioxidant peptides, the guardian of life from oxidative stress

Reactive oxygen species (ROS) are produced during oxidative metabolism in aerobic organisms. Under normal conditions, ROS production and elimination are in a relatively balanced state. However, under internal or external environmental stress, such as high glucose levels or UV radiation, ROS production can increase significantly, leading to oxidative stress. Excess ROS production not only damages biomolecules but is also closely associated with the pathogenesis of many diseases, such as skin photoaging, diabetes, and cancer. Antioxidant peptides (AOPs) are naturally occurring or artificially designed peptides that can reduce the levels of ROS and other pro-oxidants, thus showing great potential in the treatment of oxidative stress-related diseases. In this review, we discussed ROS production and its role in inducing oxidative stress-related diseases in humans. Additionally, we discussed the sources, mechanism of action, and evaluation methods of AOPs and provided directions for future studies on AOPs.

Effects of Fish Skin Gelatin Hydrolysates Treated with Alcalase and Savinase on Frozen Dough and Bread Quality

Fish skin gelatin, as a waste product of sea bream, was used to obtain fish gelatin hydrolysate (FGH) with the treatment of alcalase (alc) and savinase (sav). The functional properties of FGHs and their usage possibilities in frozen dough bread making were investigated. FGH treated with alc showed a higher emulsifying stability index (189 min), while FGH treated with sav showed greater foaming capacity (27.8%) and fat-binding capacity (1.84 mL/g). Bread doughs were produced using two FGHs (alc and sav) and their combination (FGH-alc + FGH-sav). Using FGH treated with these enzymes individually was more effective than their combination in terms of polyacrylamide gel electrophoresis (SDS-PAGE) results and bread quality (specific volume and hardness). The addition of FGH into bread dough showed no significant effect on bread dough viscoelasticity (tan δ), while the increment level of tan δ value for control dough was higher than the dough containing FGH after frozen storage (-30 °C for 30 days). The highest freezable water content (FW%) was found in control dough (33.9%) (p < 0.05). The highest specific volume was obtained for control fresh bread and bread with FGH-alc, while the lowest volume was obtained for fresh bread containing FGH-sav (p < 0.05). After frozen storage of the doughs, the bread with FGH-alc showed the highest specific volume. FGH addition caused a significant reduction in the L* (lightness) value of fresh bread samples when compared to control bread (p < 0.05). This study suggested that usage of FGH-alc in bread making decreased the deterioration effect of frozen storage in terms of the specific volume and hardness of bread.

Protein Hydrolysates from Fishery Processing By-Products: Production, Characteristics, Food Applications, and Challenges

Fish processing by-products such as frames, trimmings, and viscera of commercial fish species are rich in proteins. Thus, they could potentially be an economical source of proteins that may be used to obtain bioactive peptides and functional protein hydrolysates for the food and nutraceutical industries. The structure, composition, and biological activities of peptides and hydrolysates depend on the freshness and the actual composition of the material. Peptides isolated from fishery by-products showed antioxidant activity. Changes in hydrolysis parameters changed the sequence and properties of the peptides and determined their physiological functions. The optimization of the value of such peptides and the production costs must be considered for each particular source of marine by-products and for their specific food applications. This review will discuss the functional properties of fishery by-products prepared using hydrolysis and their potential food applications. It also reviews the structure-activity relationships of the antioxidant activity of peptides as well as challenges to the use of fishery by-products for protein hydrolysate production.

The Effect of Different pH Conditions on Peptides' Separation from the Skipjack Dark Meat Hydrolysate Using Ceramic Ultrafiltration

The conversion of Skipjack (Katsuwonus pelamis) dark meat into a hydrolysate via enzymatic hydrolysis is a promising approach to increase the value of tuna by-products as a source of bioactive peptides. Skipjack dark meat hydrolysate (SDMH) contains various sizes and sequences of peptides. To obtain and concentrate the targeted small peptides from SDMH, ultrafiltration, a key unit operation process, was employed to fractionate the protein hydrolysate due to its simplicity and productivity. The objective of this study was to investigate the effect of the feed pH on the membrane performance based on the permeate flux and the transmission of peptides. The fractionation of SDMH was performed using a ceramic membrane (molecular weight cut-off of 1 kDa) with three different pH values (5, 7, and 9) at various transmembrane pressures (TMP) (2.85, 3.85, and 4.85 bar). A high permeate flux and transmission were obtained at pH 9 due to the repulsive interactions between peptides and the membrane surface, leading to the reduction in concentration polarization that could promote high transmission. In addition, the combination of low TMP (2.85 bar) and pH 9 helped to even minimize the fouling formation tendency, providing the highest peptide transmission in this study. The fractionation process resulted in the enhancement of small peptides (MW < 0.3 kDa). The amino acid profiles were different at each pH, affirming the charge effect from the pH changes. In conclusion, the performance of the membrane was affected by the pH of the hydrolysate. Additionally, the ultrafiltration method served as an alternate method of peptide separation on a commercial scale.

Diverse uses of valuable seafood processing industry waste for sustainability: a review

Seafoods are rich in untapped bioactive compounds that have the potential to provide novel ingredients for the development of commercial functional foods and pharmaceuticals. Unfortunately, a large portion of waste or discards is generated in commercial processing setups (50-80%), which is wasted or underutilized. These by-products are a rich source of novel and valuable biomolecules, including bioactive peptides, collagen and gelatin, oligosaccharides, fatty acids, enzymes, calcium, water-soluble minerals, vitamins, carotenoids, chitin, chitosan and biopolymers. These fish components may be used in the food, cosmetic, pharmaceutical, environmental, biomedical and other industries. Furthermore, they provide a viable source for the production of biofuels. As a result, the current review emphasizes the importance of effective by-product and discard reduction techniques that can provide practical and profitable solutions. Recognizing this, many initiatives have been initiated to effectively use them and generate income for the long-term sustainability of the environment and economic framework of the processing industry. This comprehensive review summarizes the current state of the art in the sustainable valorisation of seafood by-products for human consumption. The review can generate a better understanding of the techniques for seafood waste valorisation to accelerate the sector while providing significant benefits.

An Analysis of the Plant- and Animal-Based Hydrocolloids as Byproducts of the Food Industry

Hydrocolloids are naturally occurring polysaccharides or proteins, which are used to gelatinize, modify texture, and thicken food products, and are also utilized in edible films and drug capsule production. Moreover, several hydrocolloids are known to have a positive impact on human health, including prebiotics rich in bioactive compounds. In this paper, plant-derived hydrocolloids from arrowroot (Maranta arundinacea), kuzu (Pueraria montana var lobata), Sassafras tree (Sassafras albidum) leaves, sugarcane, acorn, and animal-derived gelatin have been reviewed. Hydrocolloid processing, utilization, physicochemical activities, composition, and health benefits have been described. The food industry generates waste such as plant parts, fibers, residue, scales, bones, fins, feathers, or skin, which are often discarded back into the environment, polluting it or into landfills, where they provide no use and generate transport and storage costs. Food industry waste frequently contains useful compounds, which can yield additional income if acquired, thus decreasing the environmental pollution. Despite conventional manufacturing, the aforementioned hydrocolloids can be recycled as byproducts, which not only minimizes waste, lowers transportation and storage expenses, and boosts revenue, but also enables the production of novel, functional, and healthy food additives for the food industry worldwide.

Preparation and Antioxidant Activities of High Fischer’s Ratio Oligopeptides from Goat Whey

This study aimed to obtain high Fischer’s ratio oligopeptides from goat whey (HFO) and investigate antioxidant property of it. Hydrolysis of goat whey was done with the approach of sequential digestion of pepsin and flavourzyme. With the adsorption of aromatic amino acids by activated carbon, HFO with a Fischer’s ratio of 27.070 and a molecular weight of 200–1,000 Da were obtained, and the branched-chain amino acids accounted for 22.87%. Then the antioxidant activity of HFO was evaluated. At the concentrations of 2.0 mg/mL and 0.50 mg/mL, HFO scavenged 77.27% and 99.63% of 1,1-diphenyl-2-picrylhydrazyl and 3-ethylbenzthiazoline-6-sulphonate free radicals respectively. The scavenging rate of HFO against hydroxyl radicals reached 92.31% at the concentration of 0.25 mg/mL. Animal experiments demonstrated that HFO could moderate the changes of malondialdehyde, superoxide dismutase and glutathione peroxidase caused by CCl₄-induced oxidative stress in vivo. This study indicated that HFO from goat whey was capable of oxidation resistance both in vivo and in vitro, which provided a scientific basis for the high-value processing and application of goat milk whey.

Isolation, Purification and Structure Identification of a Calcium-Binding Peptide from Sheep Bone Protein Hydrolysate

To isolate a novel peptide with calcium-binding capacity, sheep bone protein was hydrolyzed sequentially using a dual-enzyme system (alcalase treatment following neutrase treatment) and investigated for its characteristics, separation, purification, and structure. The sheep bone protein hydrolysate (SBPH) was enriched in key amino acids such as Gly, Arg, Pro, Leu, Lys, Glu, Val, and Asp. The fluorescence spectra, circular dichroism spectra, and Fourier-transform infrared spectroscopy results showed that adding calcium ions decreased the α-helix and β-sheet content but significantly increased the random and β-turn content (p < 0.05). Carboxyl oxygen and amino nitrogen atoms of SBPH may participate in peptide−calcium binding. Scanning electron microscopy and energy dispersive spectrometry results showed that SBPH had strong calcium-chelating ability and that the peptide−calcium complex (SBPH−Ca) combined with calcium to form a spherical cluster structure. SBPH was separated and purified gradually by ultrafiltration, gel filtration chromatography, and reversed-phase high-performance liquid chromatography. Liquid chromatography-electrospray ionization/mass spectrometry identified the amino acid sequences as GPSGLPGERG (925.46 Da) and GAPGKDGVRG (912.48 Da), with calcium-binding capacities of 89.76 ± 0.19% and 88.26 ± 0.25%, respectively. The results of this study provide a scientific basis for the preparation of a new type of calcium supplement and high-value utilization of sheep bone.

Physiological and Clinical Aspects of Bioactive Peptides from Marine Animals

Biological molecules in nutraceuticals and functional foods have proven physiological properties to treat human chronic diseases. These molecules contribute to applications in the food and pharmaceutical industries by preventing food spoilage and cellular injury. Technological advancement in the screening and characterization of bioactive peptides has enabled scientists to understand the associated molecules. Consistent collaboration among nutritionists, pharmacists, food scientists, and bioengineers to find new bioactive compounds with higher therapeutic potential against nutrition-related diseases highlights the potential of the bioactive peptides for food and pharmaceutic industries. Among the popular dietary supplements, marine animals have always been considered imperative due to their rich nutritional values and byproduct use in the food and pharmaceutical industries. The bioactive peptides isolated from marine animals are well-known for their higher bioactivities against human diseases. The physiological properties of fish-based hydrolyzed proteins and peptides have been claimed through in vitro, in vivo, and clinical trials. However, systematic study on the physiological and clinical significance of these bioactive peptides is scarce. In this review, we not only discuss the physiological and clinical significance of antioxidant and anticancer peptides derived from marine animals, but we also compare their biological activities through existing in vitro and in vivo studies.

Chemical Composition, Nutritive Value, Volatile Profiles and Antioxidant Activity of Coconut (Cocos nucifera L.) Haustorium with Different Transverse Diameter

In order to promote the development and utilization of coconut haustorium (CH). The basic chemical composition, volatile profiles and antioxidant activities of three haustoria with different transverse diameters were investigated. Results showed large coconut haustorium (LCH) contained more soluble sugar (47.10%) and reducing sugar (17.68%), while small coconut haustorium (SCH) possessed more ash (10.17%), protein (9.22%) and fat (5.03%). All CH were rich in potassium (4.06–4.69%) and phosphorus (0.39–0.50%). The fatty acid composition of SCH and amino acid composition of middle coconut haustorium (MCH) was more reasonable, which indicated its relatively higher nutritive value. Acids ranging from 26.90% to 60.82% were the dominant volatile components in CH, especially isobutyric acid whose relative content in SCH was up to 56.78%. The haustorium extract with polysaccharide as the main component has certain antioxidant activities, the half eliminating concentration (EC₅₀ values) of LCH on hydroxyl radical and SCH on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical were 8.33, 1.18 and 2.44 mg/mL, respectively. These results provided a reference for the development and utilization of different CH as a raw material in functional food or dietary additives.

From Fish Scale Gelatin to Tyrosinase Inhibitor: A Novel Peptides Screening Approach Application

Bioaffinity ultrafiltration combined with LC-Orbitrap-MS/MS was applied for the first time to achieve rapid screening and identification of tyrosinase inhibitory peptides (TYIPs) from grass carp scale gelatin hydrolysates. The binding mode of TYIPs with tyrosinase was investigated by molecular docking technology. The whitening effect of TYIPs was further studied by evaluating the tyrosinase activity and melanin content in mouse B16F10 cells. Four new TYIPs were screened from hydrolysates, among which DLGFLARGF showed the strongest tyrosinase inhibition with an IC50 value of 3.09 mM. Molecular docking showed that hydrogen bonds were the main driving force in the interaction between the peptide DLGFLARGF and tyrosinase. The addition of DLGFLARGF significantly inhibited the tyrosinase activity and melanin production of B16F10 melanoma cells. These results suggest that DLGFLARGF is a promising skin whitening agent for the treatment of potential pigment-related diseases.

Electrically Switchable Nanolever Technology for the Screening of Metal-Chelating Peptides in Hydrolysates

Metal-chelating peptides (MCP) are considered as indirect antioxidants due to their capacity to inhibit radical chain reaction and oxidation. Here, we propose a new proof of concept for the screening of MCPs present in protein hydrolysates for valorizing their antioxidant properties by using the emerging time-resolved molecular dynamics technology, switchSENSE. This method unveils possible interactions between MCPs and immobilized nickel ions using fluorescence and electro-switchable DNA chips. The switchSENSE method was first set up on synthetic peptides known for their metal-chelating properties. Then, it was applied to soy and tilapia viscera protein hydrolysates. Their Cu²⁺-chelation capacity was, in addition, determined by UV-visible spectrophotometry as a reference method. The switchSENSE method has displayed a high sensitivity to evidence the presence of MCPs in both hydrolysates. Hence, we demonstrate for the first time that this newly introduced technology is a convenient methodology to screen protein hydrolysates in order to determine the presence of MCPs before launching time-consuming separations.

Structural characterization, erythrocyte protection, and antifatigue effect of antioxidant collagen peptides from tilapia (Oreochromis nilotica L.) skin

Tilapia (Oreochromis nilotica L.) skin collagen is a meritorious commercial resource to be exploited. The purpose of this study was to obtain, evaluate, and characterize tilapia skin collagen-derived antioxidant hydrolysates (TSCP). AAPH-induced erythrocyte hemolysis assay and antifatigue test in mice were implemented. It was indicated that TSCP treatment at 1 mg mL-1 could effectively attenuate AAPH-induced erythrocyte hemolysis rate from 56.35 ± 2.46% to 18.78 ± 2.48% (p < 0.01). A 2.5 mg/(10 g d) dose of TSCP intragastric administration could observably prolong the exhaustive swimming time of the loaded mice and its mechanism was multiple, including the decrease in the levels of serum lactic acid, serum urea nitrogen, and creatine kinase activity, thus improving the contents of liver and muscle glycogen and endogenous SOD activity. Five oligopeptides from the antioxidant fraction were identified as Gly-Hyp, Glu-Asp, Asp-Hyp-Gly, Glu-Pro-Pro-Phe, and Lys-Pro-Phe-Gly-Ser-Gly-Ala-Thr and then synthesized. Among them, the octapeptide exhibited the strongest antioxidant capacity. Therefore, tilapia skin-derived collagen is a meritorious edible resource for producing commercial functional foods, thus helping to scavenge radicals, protecting erythrocytes, and further resisting fatigue.

Anti-aging effect of an oral disintegrating collagen film: a prospective, single-arm study

BACKGROUND

As the average life expectancy increases, skin aging and wrinkles due to photoaging have gained attention. Collagen is closely involved in the process of skin aging. Among the potential methods of drug delivery to the skin, oral disintegrating films show promise for their ability to bypass the loss of active components that is typical of drug absorption via oral administration. This study was conducted to investigate the effect of an oral disintegrating collagen film on skin aging.

METHODS

We performed a prospective, single-arm study in a cohort of 22 women to assess the anti-aging effect of a novel oral disintegrating film containing collagen applied daily over a 12-week period. We measured the clinical indicators of skin integrity and performed immunofluorescence and high-performance liquid chromatography analyses of an ex vivo oral mucosa model to compare the absorption rates of collagen films and conventional oral tablets via the mucosa.

RESULTS

We found that the oral disintegrating collagen film reduced skin wrinkle depth and number and significantly increased skin elasticity and density.

CONCLUSIONS

The novel mode of delivery of collagen via oral disintegrating films has a clinically potential anti-aging efficacy and is safe and convenient for daily use.

Protective effect against d-gal-induced aging mice and components of polypeptides and polyphenols in defatted walnut kernel during simulated gastrointestinal digestion

Defatted walnut kernel with pellicle (WKP) is an industrial byproduct during walnut oil extraction, which is rich in protein and polyphenols. WKP was hydrolyzed by simulated gastrointestinal digestion to obtain WKP hydrolysates (WKPHs). Results showed the protein recovery and hydrolysis degree of WKPH were 82.15 and 10.36%. The total phenol contents in WKP and WKPH were 4.90 and 40.70 mg gallic acid equivalent/g, respectively. The antiaging activity of WKPH was evaluated using a d-gal-induced aging mouse model. Results showed that WKPHs could recover the activities of SOD and T-AOC and the content of MDA in tissues and serum of the aging mice. The histological morphology of liver and kidney sections and the immunohistochemistry of TNF-α, IL-1β, and IL-6 in liver were observed. WKPH could effectively protect the tissue structure of the liver and kidney and reduce the inflammatory expression of liver in aging mice. The polypeptides and polyphenols in WKPH were further analyzed. Fifty polypeptides were identified and 12 of these peptides had Leu-Arg at the C-terminal. Forty-two polyphenols were detected, and most phenolic compounds belonged to ellagitannins. This study provided a theoretical basis for the improved processing and high-value utilization of walnut byproducts. PRACTICAL APPLICATION: Defatted walnut kernel with pellicle was hydrolyzed by simulated gastrointestinal digestion to obtain its hydrolysates. The hydrolysates have good antiaging activity in vivo. Fifty polypeptides were identified and 12 of these peptides had Leu-Arg at the C-terminal. Forty-two polyphenols were detected, and most phenolic compounds belonged to ellagitannins. This study could provide a theoretical basis for high-value utilization of walnut byproducts.

Antioxidant and functional properties of cowhide collagen peptides

In the present study, antioxidant activities and functional properties of cowhide collagen antioxidant peptides (CCAPs) with different molecular weight (MW) were investigated. The optimum preparation conditions of CCAPs were hydrolysis time of 1.53 hr, temperature of 54.9 °C, pH 7.38, and neutral enzyme to trypsin ratio of 0.048 g: 0.016 g according to single factor test and response surface methodology (RSM). Three fractions (CCAP-I, CCAP-II, and CCAP-III) were obtained by ultrafiltration and lyophilization. Antioxidant activities revealed that CCAP-III had high reducing power activity (0.323 ± 0.035) and scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (64.30 ± 5.99%), 2,2-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radicals (75.25 ± 3.14%), and hydroxyl radicals (68.26 ± 6.74%) compared to the other fractions. In addition, LC-MS/MS analysis showed that Ala-Gly-Glu-Arg, Gly-Ile-Ala-Gly-Glu-Arg, Gly-Pro-Ala-Gly-Pro-Ala-Gly-Pro-Arg, Gly-Val-Val-Gly-Pro-Glu-Gly-Ala-Arg and Gly-Phe-Ser-Gly-Leu-Asp-Gly-Ala-Lys were the major peptides of CCAP-III. CCAP-III showed good hygroscopicity (HYG), water holding capacity (WHC), and oil holding capacity (OHC) when compared with CCAP-I and CCAP-II. However, CCAP-II has great emulsifying properties, and CCAP-I has excellent foaming properties. Therefore, CCAPs can be used as a promising source of functional peptides with antioxidant properties. PRACTICAL APPLICATION: This study demonstrated the peptides of cowhide collagen has superior antioxidant and functional properties. This study provided a scientific basis for the preparation of antioxidant peptides from cowhide collagen.

One- and double-layered furcellaran/carp skin gelatin hydrolysate film system with antioxidant peptide as an innovative packaging for perishable foods products

In this study, two active packaging types were produced: single-layer biopolymer films with a polysaccharide - furcellaran and carp skin gelatin hydrolysate; two-layer films with identical composition, but synthetic peptide Alanina-Tyrosine addition. The procedure objective was multiplying antioxidant effects of the hydrolysate complexed with furcellaran. Films were used on Atlantic mackerel (storage 4 °C, 15 days); samples were analysed for changes in microbiological quality, TVB-N, biogenic amine content, fatty acid composition, TBARS. Consumer analysis was performed characterising mackerel carcass perception depending on implemented active coatings. The developed innovative single- and double-layer coatings effectively slow down lipid oxidation processes, especially at the initial period of Atlantic mackerel storage in refrigerated conditions. The coatings effectively inhibited microorganism growth, extending shelf-life by 2 days, single-layer coatings showing greater efficiency. According to consumers, coating application did not adversely affect product attractiveness parameters. The developed innovative coatings show great applicative potential as a new active packaging for perishable foods.

Fish Waste: From Problem to Valuable Resource

Following the growth of the global population and the subsequent rapid increase in urbanization and industrialization, the fisheries and aquaculture production has seen a massive increase driven mainly by the development of fishing technologies. Accordingly, a remarkable increase in the amount of fish waste has been produced around the world; it has been estimated that about two-thirds of the total amount of fish is discarded as waste, creating huge economic and environmental concerns. For this reason, the disposal and recycling of these wastes has become a key issue to be resolved. With the growing attention of the circular economy, the exploitation of underused or discarded marine material can represent a sustainable strategy for the realization of a circular bioeconomy, with the production of materials with high added value. In this study, we underline the enormous role that fish waste can have in the socio-economic sector. This review presents the different compounds with high commercial value obtained by fish byproducts, including collagen, enzymes, and bioactive peptides, and lists their possible applications in different fields.

Bioactivity of Hydrolysates Obtained from Chicken Egg Ovalbumin Using Artichoke (Cynara scolymus L.) Proteases

The aim of this work was to obtain chicken egg ovalbumin hydrolysates using aspartic proteinases present in extracts from the artichoke flower (Cynara scolymus L.) and evaluate their antioxidant, antimicrobial, and angiotensin I-converting enzyme (ACE) inhibitory activity in vitro. Hydrolysis time and molecular weight (<3 kDa) had a significant influence on the hypertensive and antioxidant activity of the hydrolysates. The <3 kDa fraction of the 16 h hydrolysate had an ACE inhibitory activity with an IC₅₀ of 64.06 µg peptides/mL. The fraction <3 kDa of ovalbumin hydrolysate at 2 h of hydrolysis showed a DPPH radical scavenging activity of 30.27 µM of Trolox equivalents/mg peptides. The fraction <3 kDa of the hydrolysate of 16 h had an ABTS⁺ caption activity of 4.30 mM of Trolox equivalents/mg peptides. The fraction <3 kDa of the hydrolysate of 2 h had an iron (II) chelating activity of 32.18 µg peptides/mL. From the peptide sequences identified in the hydrolysates, we detected four peptides (from the BIOPEP database) that were already in their bioactive form (IAAEVYEHTEGSTTSY, HLFGPPGKKDPV, PIAAEVYEHTEGSTTSY, and YAEERYPIL), and are reported to display antioxidant and ACE inhibitory activity.

Tilapia viscera hydrolysate extract alleviates oxidative stress and renal damage in deoxycorticosterone acetate-salt-induced hypertension rats

Background and Aim:

Hypertension is closely related to oxidative stress conditions, which increases malondialdehyde (MDA) expression and renal damage. Tilapia viscera hydrolysate extract (TVHE) contains compounds and peptides that act as antioxidants. This study aimed to investigate TVHE therapy effect on MDA levels and renal histological conditions in deoxycorticosterone acetate (DOCA)-salt-induced hypertension rats.

Materials and Methods:

Tilapia viscera were defatted and hydrolyzed using Alcalase enzyme to obtain TVHE. TVHE antioxidant activity was measured using the 1,1-diphenyl-2-picrylhydrazyl method. Fifteen Wistar male rats were divided into five groups: Normal control (without induced DOCA-salt), DOCA-salt, DOCA-salt+Captopril 5 mg/kg body weight (BW), DOCA-salt+TVHE 150 mg/kg BW, and DOCA-salt+TVHE 300 mg/kg BW. MDA level and renal histology were observed in each group.

Results:

TVHE half maximal inhibitory concentration values ranged from 3.87±0.35 μg/mL to 42.03±3.55 μg/mL, which were identified as in the very strong Blois category. TVHE and captopril therapy reduced MDA expression significantly (p<0.05) compared to DOCA-salt only. TVHE and captopril therapy also improved glomerular damage in DOCA-salt-induced hypertension rats.

Conclusion:

TVHE has antioxidant ability, decreased MDA level, and decreased glomerular damage in DOCA-salt-induced hypertension rats.

Effect of animal-sourced bioactive peptides on the in vitro development of mouse preantral follicles

The aim of this study was to investigate the effect of bioactive peptides (BAPT) from animal sources on the development of mouse preantral follicles in vitro. Preantral follicles were isolated and randomly divided into the following groups: an untreated group (control) and three groups supplemented with 20, 40 and 60 μg/mL BAPT, respectively. After establishing the in vitro follicle culture, the gene expression levels and hormone levels were quantified. After in vitro maturation, the developmental rates, reactive oxygen species (ROS) production levels and mitochondrial distributions of MII oocytes were investigated, followed by the analyses of embryonic developmental rates after in vitro fertilization.The results showed that BAPT promoted the growth of mouse preantral follicles. Notably, after 14 d of in vitro culture, the levels of 17 β-estradiol and progesterone were up-regulated with BAPT treatments. Moreover, the expression levels of Oct4, Bmp15, GDF9, FOXO3, Zp3, FOXL2, Inhibin alpha, SOD2, Catalase, GPx and Bcl-2 in the developing follicles were significantly up-regulated after BAPT treatments (P < 0.05), while BAPT significantly inhibited the expression levels of BAX (P < 0.05). Following BAPT treatments, the ROS production levels of MII oocytes were decreased while the mitochondrial distributions were significantly enhanced. Furthermore, increased maturation rates, fertilization and embryonic developmental rates were found in these BAPT-treated groups (P < 0.05).These results demonstrated that BAPT significantly improved the development of preantral follicles in vitro by reducing ROS-dependent cellular damages and by enhancing mitochondrial distributions, thereby promoting the further applications of animal-derived BAPT in biomedical research.

Advances on Food-Derived Peptidic Antioxidants-A Review

The oxidation process is considered to be the main reason behind human aging, human degenerative diseases and food quality degradation. Food-derived peptidic antioxidants (PAs) have wide sources and great activity, and have broad application prospects in removing excess reactive oxygen species in the body, anti-aging and preventing and treating diseases related to oxidative stress. On the other hand, PAs are expected to inhibit the lipid peroxidation of foods and increase the stability of the food system in the food industry. However, the production pathways and action mechanism of food-derived PAs are diverse, which makes it is difficult to evaluate the performance of PAs which is why the commercial application of PAs is still in its infancy. This article focuses on reviewing the preparation, purification, and characterization methods of food-derived PAs, and expounds the latest progress in performance evaluation and potential applications, in order to provide an effective reference for subsequent related research of PAs.

Effect of bioactive peptide on ram semen cryopreservation

This present study investigated the effect of bioactive peptide (BAPT) (BAPT) on the quality of ram semen during cryopreservation. Ram ejaculates were extended with Tris buffer supplemented with no antioxidants (as control group), 20 μg/mL BAPT (as BAPT20 group), 40 μg/mL BAPT (as BAPT40 group) and 60 μg/mL BAPT (as BAPT60 group). After cryopreservation, sperm quality including motility, vitality, the percentage of hypoosmotic swelling test (HOST)-positive spermatozoa and the percentage of intact acrosomes was assessed. Furthermore, the malondialdehyde (MDA) in seminal plasma and spermatozoa were analyzed, followed by the measurement of superoxide dismutase (SOD), catalase (CAT) and glutathione-peroxidase (GSH-Px) levels in seminal plasma. After in vitro fertilization, the embryonic cleavage rates and development rates of different groups were analyzed to compare the developmental abilities of spermatozoa. The results showed that the post-thaw sperm motility was significantly higher in the BAPT60 group compared to those in the BAPT20, BAPT40 and control groups (P < 0.05). The percentage of live sperms significantly increased from 48.12 ± 2.35% for the BAPT20 group, 55.43 ± 2.16% for the BAPT40 group to 57.53 ± 3.15% for the BAPT60 group. The percentage of HOST-positive spermatozoa was significantly higher in the BAPT60 group than those in BAPT20, BAPT40 and control groups (P < 0.05). The MDA levels in seminal plasma and spermatozoa were significantly reduced with BAPT supplement (P < 0.05). Additionally, the SOD, CAT and GSH-Px levels in the BAPT experimental groups were significantly higher than those of the control group, which further indicated that BAPT significantly inhibit the reactive oxygen species (ROS) production during the cryopreservation of ram semen. Furthermore, the embryonic cleavage rates and development rates of the BAPT40 and BAPT60 groups were significantly increased in comparison with the BAPT20 and control groups (P < 0.05). In conclusion, BAPT improved the ram sperm quality via inhibiting the ROS production during cryopreservation, and could be applied as a promising supplement for ram semen cryopreservation.

Characterization of Proteolytic Activity of Artichoke (Cynara scolymus L.) Flower Extracts on Bovine Casein to Obtain Bioactive Peptides

Simple Summary

Recently, dairy proteins, in addition to their basic nutritional role in the diet, were recognized as a source of bioactive peptides. Such peptides are encoded within the primary structure of the protein and can be released by enzymatic hydrolysis. The growing interest in the development of functional foods for the benefit of consumer health led to a recent increase in research on the production of bioactive peptides from different matrices and production methods. The use of aspartic proteases from stigmas of mature artichoke (Cynara scolymus L.) flowers to obtain hydrolytic enzymes (cinarases) in the production of bioactive peptides would involve the utilization of an agricultural residue of a plant species of great socio-economic importance. In the present study, the characterization of the optimal hydrolysis conditions of artichoke flower extracts was carried out for the production of peptides from bovine casein. Furthermore, the angiotensin-converting enzyme-I inhibitory activity and the antioxidant capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) free radicals in vitro were determined for the obtained hydrolysates. The results revealed that the water-soluble extract of artichoke flower could be suitable for the production of bioactive peptides from whole bovine casein.

Abstract

The aim of this work is to establish the most suitable proteolysis conditions to obtain bovine casein hydrolysates containing peptides with antioxidant and antihypertensive capacity. To this end, the proteolytic activity of Cynara scolymus L. flower extracts was characterized on whole bovine casein, evaluating the effect of several factors (pH, temperature, substrate concentration, enzyme concentration, and hydrolysis time). The optimal conditions to carry out the hydrolysis with the C. scolymus L. extract were as follows: pH 6.2, 50 °C, and 0.023 mg·mL⁻¹ of extract-protein concentration. A Michaelis constant (K_m) value of 5.66 mg·mL⁻¹ and a maximum rate of reaction (V_max) of 8.47 mUAbs∙min⁻¹ were observed. The optimal hydrolysis time was 17 h. The casein hydrolysates obtained with these conditions contained peptides with antioxidant activity (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity: 30.89%; Trolox equivalent antioxidant capacity (TEAC) against 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) free radical (ABTS^●+): 4.43 mM Trolox equivalent·mg⁻¹ peptide) and antihypertensive activity, showing 55.05% angiotensin-converting enzyme-I inhibition in vitro.

Identification and characterization of novel antioxidant peptides from mackerel (Scomber japonicus) muscle protein hydrolysates

Antioxidant peptides are commonly used as functional ingredient in the pharmaceutical industries. Here, we characterized the antioxidant peptides from mackerel muscle protein hydrolysates (MPHs). MPHs showing higher bioactivities were separated into seven groups by FPLC. MPH-3 which exhibited significantly higher (p < 0.05) DPPH scavenging activity (32.12 ± 3.01%) was fractionated using RP-HPLC to obtain purified fractions A and B, which were further subjected to MALDI-TOF/TOF-MS for mass fingerprinting. Fraction A exhibited the highest (p < 0.05) DPPH scavenging activity (34.11 ± 1.52%), and it contained 21 peptides characterized by LC-MS/MS-. Ten peptides were synthesized, and their antioxidant activities were evaluated; one of the peptides, ALSTWTLQLGSTSFSASPM, showed the highest (p < 0.05) DPPH scavenging activity (36.34 ± 4.64%) and another peptide, LGTLLFIAIPI, exhibited the highest (p < 0.05) SOD-like activity (28.94 ± 4.19%). The results of this study indicate that MPHs could serve as a suitable source of antioxidant peptides.

Radical scavenging activities of peptide from Asian clam (Corbicula fluminea) and its protective effects on oxidative damage induced by hydrogen peroxide in HepG2 cells

The soft part of Asian clam (Corbicula fluminea) was hydrolyzed using trypsin and the hydrolysates were separated by ultrafiltration using the membrane with molecular weight cutoff of 10 and 5 kDa. Three fractions (F10000, F10000-5000, and F5000) were obtained. The F5000 showed the strongest scavenging abilities to DPPH (2,2-diphenyl-1-picrylhydrazyl), superoxide anion, and hydroxyl radicals, and was further fractionated into four fractions (component I, II, III, and IV) by gel chromatography. The protective effects of these components on oxidative damage induced by hydrogen peroxide (H₂ O₂ ) in HepG2 cells were evaluated. Meanwhile, component I separated from F5000 had more positive effects on increasing the activity of catalase, decreasing lipid peroxidation, inhibiting H₂ O₂ -induced apoptosis, and higher yield. The component I was further separated using anion exchange chromatography and reversed phase high-performance liquid chromatography, and the peptide sequence of Lys-Gly-Pro-Ala- Pro-Phe-Tyr-Pro-Leu was identified by mass with molecular weight of 988.3 Da. PRACTICAL APPLICATIONS: Asian clam (C. fluminea) is used for liver protection in traditional Chinese medicine. The present study investigated the radical scavenging activity of the hydrolysates from C. fluminea and the protective effects of the hydrolysate fractions on oxidative damage induced by H₂ O₂ in HepG2 cells. In addition, a peptide was purified from the hydrolysate and the amino acid sequence of it was identified. Although chemical antioxidant has some side effects on health, the peptide with antioxidant activity obtained from C. fluminea would have more extensive application in food and nutraceutical.

Physicochemical properties and hepatoprotective effects of glycated Snapper fish scale peptides conjugated with xylose via maillard reaction

The physicochemical properties and hepatoprotective effects of fish scales peptides (FSP) and the glycated peptides conjugated with xylose via Maillard reaction (FSP-MRPs) were investigated. Results showed that the FSP was rich in oligopeptides within 2-10 amino acids, the degree of grafting of FSP-MRPs was 52.97 ± 1.58% and the antioxidant activities in vitro of FSP were improved through Maillard reaction. In order to investigate the antioxidant activities of FSP-MRPs after digestion, the simulated gastrointestinal digestion experiments of FSP and FSP-MRPs in vitro were conducted. Results indicated that the antioxidant activities of FSP and FSP-MRPs remained as stronger as before even under the digestive conditions. Furthermore, FSP-MRPs could significantly reduce the elevated activities of serum aspartate aminotransferase and alanine aminotransferase, decrease the elevated the levels of hepatic malondialdehyde and triglyceride, and inhibit the decrease of hepatic superoxide dismutase, catalase and glutathione peroxidase caused by alcohol-induced liver damage. These findings suggest that the glycated peptides formed by FSP and xylose via Maillard reaction may be potential to be exploited as a potential functional ingredient in food industry.

Isolation of antioxidant peptides from yak casein hydrolysate

Enzymatic hydrolysis of protein is a principal method to obtain antioxidant peptides. A yak casein hydrolysate (YCH) was prepared by alcalase and trypsin digestion. An ultrafiltration membrane system was used to divide the hydrolysate into four molecular weight fractions; YCH-4 (<3 kDa) had the highest antioxidant activity. Fraction YCH-4 was separated into six subfractions by gel filtration chromatography; reverse-phase high performance liquid chromatography (RP-HPLC) was then used to partition sixteen antioxidant peptide subfractions. Liquid chromatography/electrospray tandem mass spectrometry (LC-ESI-MS/MS) was used to determine the amino acid sequence of a purified antioxidant peptide to be Arg-Glu-Leu-Glu-Glu-Leu (787.41 Da). Finally, a synthetic Arg-Glu-Leu-Glu-Glu-Leu peptide was evaluated for its superoxide anion and hydroxyl radical scavenging activity (IC₅₀ = 0.52 and 0.69 mg mL⁻¹), which confirmed the activity of the native purified peptide. Our results suggested that isolation and purification of antioxidant peptides from yak casein could be an important means to obtain natural antioxidant peptides.

Enzymatic hydrolysis of protein is a principal method to obtain antioxidant peptides.

Bioactive peptides derived from crimson snapper and in vivo anti-aging effects on fat diet-induced high fat Drosophila melanogaster

Crimson snapper scale peptides (CSSPs) prepared from crimson snapper scales exhibited significant antioxidant activity in vitro and anti-aging effects in vivo on fat diet-induced high fat Drosophila melanogaster.

Identification and characterization of the peptides with calcium-binding capacity from tilapia (Oreochromis niloticus) skin gelatin enzymatic hydrolysates

The aim of this study was to isolate and identify the peptides with calcium-binding capacity from the different tilapia skin gelatin enzymatic hydrolysates. The complex protease was selected and its hydrolysates were further separated using gel filtration chromatography (Sephadex G-25) and reverse phase high-performance liquid chromatography. Two purified peptides with strong calcium-binding capacity were identified as Tyr-Gly-Thr-Gly-Leu (YGTGL, 509.25 Da) and Leu-Val-Phe-Leu (LVFL, 490.32 Da). The calcium-binding capacities of YGTGL and LVFL reached 76.03 and 79.50 µg/mg, respectively. The structures of the complex of purified peptides and calcium (YGTGL-Ca and LVFL-Ca) were characterized by ultraviolet-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry (LC-MS/MS). The results of UV-VIS, SEM, and XRD indicated that YGTGL-Ca and LVFL-Ca were formed as new compounds. The results of FTIR and LC-MS/MS indicated the nitrogen atom of the amino group and the oxygen atom of the carboxyl group in terminates of the peptides provided primary binding sites. Moreover, the hydrophobic amino acids in purified peptides could provide more chelating spaces. This study was of great significance for the development of calcium supplement foods. PRACTICAL APPLICATION: Compared with inorganic calcium and organic calcium, the bioactive gelatin peptide chelated calcium has the characteristics of high utilization rate, high solubility, and high absorption rate. The raw materials are extracted from the tilapia processed waste, which reduce the cost, make full use of resources, and improve the bioavailability. The tilapia skin gelatin peptide calcium chelate can be directly absorbed by the human body, and the absorption efficiency is high, further improving the resource utilization rate and having high economic benefits, which is a comprehensive supplement that can also be used as a functional food.

Identification and characterization of novel antioxidant peptides from crucian carp (Carassius auratus) cooking juice released in simulated gastrointestinal digestion by UPLC-MS/MS and in silico analysis

The objective of this work was to separate, identify and assess antioxidant peptides from the simulated gastrointestinal (GI) digestion of crucian carp (Carassius auratus) cooking juice (CCCJ), which has been previously found with this activity. The CCCJ after simulated GI digestion treatment was separated gradually by ultrafiltration and RP-HPLC. Five novel antioxidant peptides with 10-13 amino acid residues were identified by UPLC-MS/MS. Their in silico assessments showed amphiphilic nature, good sensory quality and different target sites in the human body. Meanwhile, their three-dimensional structure predictions exhibited at least one β-turn, β-sheet and/or α-helix with partial hydrophobic and/or net-charged residues exposed to the external medium, which was good evidence for high antioxidant activity. Ultimately, four novel peptides with high antioxidant activity were found, among which IREADIDGDGQVN (1401 Da), PEILPDGDHD (1107 Da) and ASDEQDSVRL (1119 Da) exerted the highest DPPH radical scavenging activity with IC₅₀ of 1.78, 1.18 and 1.45 mM, respectively, while APLEEPSSPH (1063 Da) showed the highest Fe²⁺ chelating ability with IC₅₀ of 0.09 mM. This work could help understand the mechanism of CCCJ on human health promotion and improve the economic value of the crucian carp processing industry.