Purification and characterization of antioxidant peptide from hoki (Johnius belengerii) frame protein by gastrointestinal digestion

Antioxidant peptides from silver carp steak by alkaline protease and flavor enzyme hydrolysis: Characterization of their structure and cytoprotective effects against H2O2-induced oxidative stress

Silver carp steak is a rarely utilized silver carp processing byproduct. This study aimed to optimize a dual enzymatic method to extract antioxidant peptide components from silver carp steak and characterize their structure and in vitro antioxidant activity through ultrafiltration purification, response surface methodology, molecular docking, and radical scavenging activity analysis. The optimal extraction conditions for silver carp steak antioxidant peptides (SCSAP) were determined as 1:6 solid-liquid ratio, 1500 U/g alkaline protease addition, 4 h alkaline protease hydrolysis time, 1946 U/g flavor enzyme addition, and 2.5 h flavor enzyme hydrolysis time. The <3 kDa SCSAP component (SCSAP-3kDa) showed the strongest antioxidant activity, with its 1,1-diphenyl-2-trinitrophenyl hydrazine (DPPH) radical scavenging rate, ABTS radical scavenging rate, hydroxyl radical scavenging rate, metal ion chelating rate, and reducing capacity reaching 88.75%, 91.21%, 67.02%, 69.07%, and 0.985, respectively. Moreover, the three peptides (PF-7, GP-8, and YF-10) of 100 µg/mL could protect HepG2 cells from oxidative stress damage by reducing the oxidative damage level and activating Keap1-Nrf2-ARE pathways, enabling an increase of superoxide dismutases (SOD) activity, and a decrease of malondialdehyde (MDA) content and reactive oxygen species (ROS) level. The integrated results indicate the enormous potential of SCSAP-3kDa as a functional food ingredient in the food industry. PRACTICAL APPLICATION: This study selected the antioxidant capacity of silver carp steak peptides as the index and developed a facile dual enzymatic hydrolysis method to obtain three antioxidant peptides (PF-7, GP-8, and YF-10) with biological activity, providing a theoretical basis for bioavailability of antioxidant peptides from silver carp steak and contributing to their application in new functional foods.

Marine Peptides: Potential Basic Structures for the Development of Hybrid Compounds as Multitarget Therapeutics for the Treatment of Multifactorial Diseases

Marine-derived peptides display potent antihypertensive, antioxidant, analgesic and antimicrobial biological effects. Some of them have also been found to have anticancer activity via various mechanisms differing from those of continental organisms. This diversity of properties-together with the peptides' efficacy, which has been confirmed in several in vitro and in vivo studies-make these compounds attractive as functional ingredients in pharmacy, especially in regard to multitarget drugs known as hybrids. Given the possibilities offered by chimeric structures, it is expected that a hybridization strategy based on a marine-derived compound could result in a long-awaited success in the development of new effective compounds to combat a range of complex diseases. However, despite the fact that the biological activity of such new hybrids may exceed that of their parent compounds, there is still an urgent need to carefully determine their potential off-targets and thus possible clinically important side effects. Given the above, the aim of this paper is to provide information on compounds of marine origin with peptide structures and to verify the occurrence and usage of hybrid compounds built from these structures. Furthermore, the authors believe that information presented here will serve to increase public awareness of the new opportunities arising from the combination of hybridization strategies with marine molecules with known structures and biological properties, thereby accelerating the development of effective drug candidates.

Antioxidant Activity of Protein Hydrolysates from Redlip Mullet (Chelon haematocheilus) Muscle and Byproducts

Fish muscle and byproducts represent a valuable source of bioactive compounds, with their protein hydrolysates exhibiting noteworthy antioxidant properties. This study assessed the antioxidant activity of protein hydrolysates derived from the muscle and byproducts of redlip mullet (Chelon haematocheilus), utilizing different proteases (Neutrase, Alcalase, and Protamex). Hydrolysates were prepared from various parts of the fish, including muscle (white and red meat) and byproducts (frames, head, viscera, fins, skin, and scales). The enzymatic hydrolysis resulted in the highest degree of hydrolysis, achieving 83.24 ± 1.45% for skin at 60 min and 82.14 ± 4.35% for head at 30 min, when treated with Neutrase. Frames treated with Neutrase exhibited the highest protein concentration, measured at 1873.01 ± 71.11 µg/mL at 15 min. Significantly, skin hydrolysates treated with Protamex showed the highest DPPH• scavenging activity (70.07 ± 3.99% at 120 min), while those treated with Alcalase demonstrated the highest ABTS• scavenging activity (93.47 ± 0.02% at 15 min). The highest superoxide dismutase (SOD) activity (92.01 ± 1.47%) was observed in head hydrolysates treated with Protamex after 90 min. These results suggest that C. haematocheilus protein hydrolysates possess significant antioxidant activity within a short time frame of less than 120 min.

Crassostrea gigas peptide PEP-1 prevents tert-butyl hydroperoxide (t-BHP) induced oxidative stress in HepG2 cells

Exposure to tert-butyl hydroperoxide (t-BHP) leads to cytotoxicity and oxidative stress in various organs and cell types. The bioactive peptides extracted from Oysters exhibit marked antioxidant activity. The impacts of Crassostrea gigas peptides on t-BHP-triggered oxidative stress remain largely unknown. The protective and antioxidant activity of a C.gigas peptide, PEP-1, on t-BHP-treated HepG2 cells, was investigated. PEP-1, this peptide is arginine kinase in oysters. This enzyme functions as a catalyst for the chemical reaction and serves as a phosphate transferase. Since it was the most expressed protein in the adductor muscle of oysters. Our determination showed the lowest level of a toxic concentration of t-BHP (200 µM) and the resting concentration of PEP-1 (0-1000 ng/ml). PEP-1 exerted a protective effect against t-BHP-induced apoptosis by modifying the expression of pro-and anti-apoptotic proteins. PEP-1 administration reduced nitric oxide and ROS levels while restoring levels of antioxidant proteins in t-BHP-induced cells. PEP-1 exhibited the capacity to enhance the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2). Therefore, the C. gigas peptide PEP-1 has demonstrated its ability to protect HepG2 cells against oxidative stress induced by t-BHP.

The Antioxidant Mechanism of Peptides Extracted from Tuna Protein Revealed Using a Molecular Docking Simulation

Tuna protein serves as a significant source of bioactive peptides, and its functional properties can be elucidated through predictive modeling, followed by experimental validation. In this study, the active polypeptides were obtained from tuna protein via enzymatic hydrolysis (TPP), and their peptide sequences were determined. Furthermore, the potential activity of these peptides was predicted, focusing on antioxidant peptides, and compared to the sequence library of known antioxidant peptides to identify common structural motifs. The accuracy of the prediction results was confirmed through in vitro antioxidant assays and molecular docking studies. We identified seven specific peptide segments derived from tuna protein that exhibit antioxidant potential, accounting for approximately 15% of all active peptides. Molecular docking and cell experiments were employed to provide compelling evidence for the presence of antioxidant peptides within tuna protein. This study not only lays a solid foundation for studying the structure of active peptides but also opens up a novel avenue for an expedited assessment of their properties.

Exploring the Potential of Bioactive Peptides: From Natural Sources to Therapeutics

Bioactive peptides, specific protein fragments with positive health effects, are gaining traction in drug development for advantages like enhanced penetration, low toxicity, and rapid clearance. This comprehensive review navigates the intricate landscape of peptide science, covering discovery to functional characterization. Beginning with a peptidomic exploration of natural sources, the review emphasizes the search for novel peptides. Extraction approaches, including enzymatic hydrolysis, microbial fermentation, and specialized methods for disulfide-linked peptides, are extensively covered. Mass spectrometric analysis techniques for data acquisition and identification, such as liquid chromatography, capillary electrophoresis, untargeted peptide analysis, and bioinformatics, are thoroughly outlined. The exploration of peptide bioactivity incorporates various methodologies, from in vitro assays to in silico techniques, including advanced approaches like phage display and cell-based assays. The review also discusses the structure-activity relationship in the context of antimicrobial peptides (AMPs), ACE-inhibitory peptides (ACEs), and antioxidative peptides (AOPs). Concluding with key findings and future research directions, this interdisciplinary review serves as a comprehensive reference, offering a holistic understanding of peptides and their potential therapeutic applications.

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 Bioactive Peptides from Atlantic Salmon Processing By-Products on Oxyntopeptic and Enteroendocrine Cells of the Gastric Mucosa of European Seabass and Gilthead Seabream

The present study was designed to evaluate the effects of dietary levels of bioactive peptides (BPs) derived from salmon processing by-products on the presence and distribution of peptic cells (oxyntopeptic cells, OPs) and enteric endocrine cells (EECs) that contain GHR, NPY and SOM in the gastric mucosa of European seabass and gilthead seabream. In this study, 27 seabass and 27 seabreams were divided into three experimental groups: a control group (CTR) fed a control diet and two groups fed different levels of BP to replace fishmeal: 5% BP (BP5%) and 10% BP (BP10%). The stomach of each fish was sampled and processed for immunohistochemistry. Some SOM, NPY and GHR-IR cells exhibited alternating "open type" and "closed type" EECs morphologies. The BP10% group (16.8 ± 7.5) showed an increase in the number of NPY-IR cells compared to CTR (CTR 8.5 ± 4.8) and BP5% (BP10% vs. CTR p ≤ 0.01; BP10% vs. BP5% p ≤ 0.05) in the seabream gastric mucosa. In addition, in seabream gastric tissue, SOM-IR cells in the BP 10% diet (16.8 ± 3.5) were different from those in CTR (12.5 ± 5) (CTR vs. BP 10% p ≤ 0.05) and BP 5% (12.9 ± 2.5) (BP 5% vs. BP 10% p ≤ 0.01). EEC SOM-IR cells increased at 10% BP (5.3 ± 0.7) compared to 5% BP (4.4 ± 0.8) (5% BP vs. 10% BP p ≤ 0.05) in seabass. The results obtained may provide a good basis for a better understanding of the potential of salmon BPs as feed ingredients for seabass and seabream.

The Effects and Regulatory Mechanism of Casein-Derived Peptide VLPVPQK in Alleviating Insulin Resistance of HepG2 Cells

The liver plays a key role in keeping the homeostasis of glucose and lipid metabolism. Insulin resistance of the liver induced by extra glucose and lipid ingestion contributes greatly to chronic metabolic disease, which is greatly threatening to human health. The small peptide, VLPVPQK, originating from casein hydrolysates of milk, shows various health-promoting functions. However, the effects of VLPVPQK on metabolic disorders of the liver are still not fully understood. Therefore, in the present study, the effects and regulatory mechanism of VLPVPQK on insulin-resistant HepG2 cells was further investigated. The results showed that VLPVPQK exerted strong scavenging capacities against various free radicals, including oxygen radicals, hydroxyl radicals, and cellular reactive oxygen species. In addition, supplementation of VLPVPQK (62.5, 125, and 250 μM) significantly reversed the high glucose and fat (30 mM glucose and 0.2 mM palmitic acid) induced decrement of glucose uptake in HepG2 cells without affecting cell viability. Furthermore, VLPVPQK intervention affected the transcriptomic profiling of the cells. The differentially expressed (DE) genes (FDR < 0.05, and absolute fold change (FC) > 1.5) between VLPVPQK and the model group were mostly enriched in the carbohydrate metabolism-related KEGG pathways. Interestingly, the expression of two core genes (HKDC1 and G6PC1) involved in the above pathways was dramatically elevated after VLPVPQK intervention, which played a key role in regulating glucose metabolism. Furthermore, supplementation of VLPVPQK reversed the high glucose and fat-induced depression of AKR1B10. Overall, VLPVPQK could alleviate the metabolic disorder of hepatocytes by elevating the glucose uptake and eliminating the ROS, while the HKDC1 and AKR1B10 genes might be the potential target genes and play important roles in the process.

Novel Antioxidant Peptides Identified from Arthrospira platensis Hydrolysates Prepared by a Marine Bacterium Pseudoalteromonas sp. JS4-1 Extracellular Protease

Crude enzymes produced by a marine bacterium Pseudoalteromonas sp. JS4-1 were used to hydrolyze phycobiliprotein. Enzymatic productions showed good performance on DPPH radical and hydroxyl radical scavenging activities (45.14 ± 0.43% and 65.11 ± 2.64%, respectively), especially small peptides with MWCO <3 kDa. Small peptides were fractioned to four fractions using size-exclusion chromatography and the second fraction (F2) had the highest activity in hydroxyl radical scavenging ability (62.61 ± 5.80%). The fraction F1 and F2 both exhibited good antioxidant activities in oxidative stress models in HUVECs and HaCaT cells. Among them, F2 could upregulate the activities of SOD and GSH-Px and reduce the lipid peroxidation degree to scavenge the ROS to protect Caenorhabditis elegans under adversity. Then, 25 peptides total were identified from F2 by LC-MS/MS, and the peptide with the new sequence of INSSDVQGKY as the most significant component was synthetized and the ORAC assay and cellular ROS scavenging assay both illustrated its excellent antioxidant property.

Antioxidant and protective effects of a peptide (VTAL) derived from simulated gastrointestinal digestion of protein hydrolysates of Magallana gigas against acetaminophen-induced HepG2 cells

Oxidative stress is an automatic mechanism responsible for the commencement and continuance of liver injury. In this study, an antioxidative peptide Val-Thr-Ala-Leu (VTAL) was purified from simulated gastrointestinal digestion of protein hydrolysates of the triploid oyster Magallana gigas. Significant antioxidant activity was identified, as well as a protective effect against acetaminophen (APAP)-induced human liver cancer (HepG2) cells. The results suggested that the antioxidant activity improved in a dose-dependent manner. The highest cell viability (88.105 ± 3.62%) was observed in 15 mM APAP-induced cells when treated with 25 μg/mL M. gigas peptide [M.g (pep)]. The peptide sequences include hydrophobic amino acids, which could be responsible for its chemoprotective and antioxidant activities. Treatment with M.g (pep) significantly promoted the proliferation of HepG2 cells, thus protecting them against APAP and imbuing them with significant antioxidant capacity. M.g (pep) could be beneficial for treating drug-induced oxidative stress and liver damage. Additionally, M.g (pep) could serve as an alternative to synthetic antioxidant drugs.

Potential Cosmetic Active Ingredients Derived from Marine By-Products

The market demand for marine-based cosmetics has shown a tremendous growth rate in the last decade. Marine resources represent a promising source of novel bioactive compounds for new cosmetic ingredient development. However, concern about sustainability also becomes an issue that should be considered in developing cosmetic ingredients. The fisheries industry (e.g., fishing, farming, and processing) generates large amounts of leftovers containing valuable substances, which are potent sources of cosmeceutical ingredients. Several bioactive substances could be extracted from the marine by-product that can be utilized as a potent ingredient to develop cosmetics products. Those bioactive substances (e.g., collagen from fish waste and chitin from crustacean waste) could be utilized as anti-photoaging, anti-wrinkle, skin barrier, and hair care products. From this perspective, this review aims to approach the potential active ingredients derived from marine by-products for cosmetics and discuss the possible activity of those active ingredients in promoting human beauty. In addition, this review also covers the prospect and challenge of using marine by-products toward the emerging concept of sustainable blue cosmetics.

Proteomics Characterization of Food-Derived Bioactive Peptides with Anti-Allergic and Anti-Inflammatory Properties

Bioactive peptides are found in foods and dietary supplements and are responsible for health benefits with applications in human and animal medicine. The health benefits include antihypertensive, antimicrobial, antithrombotic, immunomodulatory, opioid, antioxidant, anti-allergic and anti-inflammatory functions. Bioactive peptides can be obtained by microbial action, mainly by the gastrointestinal microbiota from proteins present in food, originating from either vegetable or animal matter or by the action of different gastrointestinal proteases. Proteomics can play an important role in the identification of bioactive peptides. High-resolution mass spectrometry is the principal technique used to detect and identify different types of analytes present in complex mixtures, even when available at low concentrations. Moreover, proteomics may provide the characterization of epitopes to develop new food allergy vaccines and the use of immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. In addition, food-derived bioactive peptides have been investigated for their anti-inflammatory properties to provide safer alternatives to nonsteroidal anti-inflammatory drugs (NSAIDs). All these bioactive peptides can be a potential source of novel drugs and ingredients in food and pharmaceuticals. The following review is focused on food-derived bioactive peptides with antiallergic and anti-inflammatory properties and summarizes the new insights into the use of proteomics for their identification and quantification.

Therapeutic Potential of Marine Bioactive Peptides against Human Immunodeficiency Virus: Recent Evidence, Challenges, and Future Trends

Acquired immunodeficiency syndrome (AIDS) is a chronic and potentially fatal ailment caused by the human immunodeficiency virus (HIV) and remains a major health problem worldwide. In recent years, the research focus has shifted to a greater emphasis on complementing treatment regimens involving conventional antiretroviral (ARV) drug therapies with novel lead structures isolated from various marine organisms that have the potential to be utilized as therapeutics for the management of HIV-AIDS. The present review summarizes the recent developments regarding bioactive peptides sourced from various marine organisms. This includes a discussion encompassing the potential of these novel marine bioactive peptides with regard to antiretroviral activities against HIV, preparation, purification, and processing techniques, in addition to insight into the future trends with an emphasis on the potential of exploration and evaluation of novel peptides to be developed into effective antiretroviral drugs.

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.

Production of Demineralized Antibacterial, Antifungal and Antioxidant Peptides from Bovine Hemoglobin Using an Optimized Multiple-Step System: Electrodialysis with Bipolar Membrane

Numerous studies have shown that bovine hemoglobin, a protein from slaughterhouse waste, has important biological potential after conventional enzymatic hydrolysis. However, the active peptides could not be considered pure since they contained mineral salts. Therefore, an optimized multi-step process of electrodialysis with bipolar membranes (EDBM) was carried out to produce discolored and demineralized peptides without the addition of chemical agents. The aim of this study was to test the antibacterial, antifungal and antioxidant activities of discolored and demineralized bovine hemoglobin hydrolysates recovered by EDBM and to compare them with raw and discolored hydrolysates derived from conventional hydrolysis. The results demonstrate that discolored–demineralized hydrolysates recovered from EDBM had significant antimicrobial activity against many bacterial (gram-positive and gram-negative) and fungal (molds and yeast) strains. Concerning antibacterial activity, lower MIC values for hydrolysates were registered against Staphylococcus aureus, Kocuria rhizophila and Listeria monocytogenes. For antifungal activity, lower MIC values for hydrolysates were registered against Paecilomyces spp., Rhodotorula mucilaginosa and Mucor racemosus. Hemoglobin hydrolysates showed fungicidal mechanisms towards these fungal strains since the MFC/MIC ratio was ≤4. The hydrolysates also showed a potent antioxidant effect in four different antioxidant tests. Consequently, they can be considered promising natural, low-salt food preservatives. To the best of our knowledge, no previous studies have identified the biological properties of discolored and demineralized bovine hemoglobin hydrolysates.

Functional dairy products as a source of bioactive peptides and probiotics: current trends and future prospectives

Milk is an incredibly healthy food world-wide. However, the 'lactase deficient' individuals cannot digest milk's carbohydrate lactose. A large part of the world population is depriving of highly beneficial milk proteins like casein, lactoalbumin, lactoglobulin, etc. due to lactose intolerance. Production of functional foods and bioactive peptides from milk with natural antioxidants and the addition of probiotics could be the best alternative to extend the use of milk functionalities. Among different probiotics, the lactic acid bacteria (LAB) like Lactobacillus delbrueckii sub sp. bulgaricus, Streptococcus thermophilus and some species of Bifidobacteria and their metabolites (paraprobiotics and postbiotics) have been given more preference to add in milk-derived functional foods. These species are generally considered as heat-tolerant, highly proteolytic, and peptidolytic towards milk proteins and they liberate smaller molecules of bioactive peptides during fermentation and other processes that stimulate the enzyme lactase to help people in digestion of milk carbohydrate lactose. Moreover, the incorporation of natural antioxidants in yoghurt and other dairy products prevents the rancidity of milk fat. The level of bioactive peptides produced in milk-derived functional foods can be determined by capillary zone electrophoresis, mass spectrometry, fractionation, and other modern assessment techniques. Commercial production of functional probiotic products with bioactive peptides could significantly contribute to reduce milk spoilage, enhance health benefits as well as the growth of the agro-processing industry.

Antioxidant properties of papain mediated protein hydrolysates from fresh water carps (Catla catla, Labeo rohita and Cirrhinus mrigala) and its application on inhibition of lipid oxidation in oil sardine mince during ice storage

Fish protein hydrolysates (FPH) from fresh water carps Catla catla, Labeo rohita and Cirrhinus mrigala were prepared with 5, 10, 15 and 20% degree of hydrolysis (DH) using papain enzyme. FPH were evaluated for antioxidant properties using in vitro assays such as DPPH free radical scavenging activity (at 10 mg/ml), ferric reducing antioxidant power assay (at 20 mg/ml) and linoleic acid peroxidation inhibition activity (at 10 mg/ml). Antioxidant properties of FPH varied with species and DH. The DPPH radical scavenging activity, linoleic acid peroxidation inhibition activity and ferric reducing antioxidant power (as absorbance at 700 nm) of FPH from carps was in the range of 59-92%, 52-85% and 0.388-0.663 respectively. Based on the overall antioxidant activity, FPH from C. catla with 20% DH was added to oil sardine mince at different concentration (0.1, 0.2 and 0.4%) and found to inhibit effectively the formation of peroxides and malonaldehyde in dose dependent manner. FPH from C. catla with 20% DH was fractionated using size exclusion chromatography and had three different peptide fractions with the approximate molecular weight of 6561-2106 Da (fraction 1), 1942-994 Da (fraction 2) and 935-383 Da (fraction 3). The present study showed promising results that the fish protein hydrolysates from fresh water carps muscle proteins can be used as natural antioxidants in food system. Production of fish protein hydrolysates with nutraceutical properties could be the way forward for better utilization and value addition.

A critical review on the health benefits of fish consumption and its bioactive constituents

As one of food sources, fish provides sufficient nutrition to human. Diverse nutrients in fish make fish an important nutrient source available easily across the globe. Fish is proven to possess several health benefits, such as anti-oxidation, anti-inflammation, wound healing, neuroprotection, cardioprotection, and hepatoprotection properties. Fish proteins, such as immunoglobins, act as defense agents against viral and bacterial infections and prevent protein-calorie malnutrition. Besides, fish oil constituents, such as polyunsaturated fatty acids (PUFAs), regulate various signaling pathways, such as nuclear factor kappa B pathway, Toll-like receptor pathway, transforming growth factor-β (TGF-β) pathway, and peroxisome proliferators activated receptor (PPAR) pathways. In this review, the literature about health benefits of fish consumption are accumulated from PubMed, Google Scholar, Scopus, and the mechanistic action of health benefits are summarized. Fish consumption at least twice per week as part of a healthy diet is beneficial for a healthy heart. More advances in this field could pose fish as a major nutrients source of foods.

Bioactive Peptides: Synthesis, Sources, Applications, and Proposed Mechanisms of Action

Bioactive peptides are a group of biological molecules that are normally buried in the structure of parent proteins and become active after the cleavage of the proteins. Another group of peptides is actively produced and found in many microorganisms and the body of organisms. Today, many groups of bioactive peptides have been marketed chemically or recombinantly. This article reviews the various production methods and sources of these important/ubiquitous and useful biomolecules. Their applications, such as antimicrobial, antihypertensive, antioxidant activities, blood-lipid-lowering effect, opioid role, antiobesity, ability to bind minerals, antidiabetic, and antiaging effects, will be explored. The types of pathways proposed for bioactive applications will be in the next part of the article, and at the end, the future perspectives of bioactive peptides will be reviewed. Reading this article is recommended for researchers interested in various fields of physiology, microbiology, biochemistry, and nanotechnology and food industry professionals.

Effect of enzymatic hydrolyzed protein from pig bones on some biological and functional properties

Pig bone residue is considered a potential source of hydrolysates from its protein with added value uses in the food industry. This work deals with the enzyme hydrolysis of pig bone protein. The conditions for extracting the protein hydrolysate were optimized and the equation obtained allowed samples with different degrees of hydrolysis (DH) to be extracted to study how the biological properties of in-vitro hydrolized protein affected digestibility, determination of the inhibitory activity of the angiotensin-converting enzyme and the antioxidant activity and its functional properties. It was found that the emulsifying capacity and emulsion stability increased at intermediate DH values, after which these properties decreased with the increase in DH. The in-vitro digestibility and angiotensin-converting enzyme (ACE) of the hydrolysates are also clearly affected by the DH. The amino acid composition of the hydrolized protein is also determined.

Antioxidant activity of SSeCAHK in HepG2 cells: a selenopeptide identified from selenium-enriched soybean protein hydrolysates

This paper is aimed at purifying and identifying selenium (Se)-containing antioxidative peptides from Se-enriched soybean peptides (SSP). In this work, the SSP was separated into five fractions (F1 to F5). Fraction F4, displaying the highest antioxidative activity, was further separated, and sub-fractions F4-1 to F4-5 were selected for antioxidative activity evaluation using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azino-bis-(3-ethylbenzo-thiazoline-6-sulphonic acid)diammonium salt (ABTS), and OH- radical scavenging assays. The Se-containing antioxidative peptides with sequence Ser-SeC-Ala-His-Lys (SSeCAHK) were identified in sub-fraction F4-1 and chemically synthesized. This Se-containing pentapeptide showed a preventive effect against hydrogen peroxide (H2O2)-induced oxidative stress in HepG2 cells. Pretreating the cells for 2 h with SSeCAHK (0.13-0.50 mg mL-1) induced strong intracellular, reactive oxygen species (ROS) scavenging activity while preventing a decrease in reduced glutathione (GSH) and an increase in malondialdehyde (MDA). Therefore, SSeCAHK treatment improved H2O2-induced oxidative stress in HepG2 cells, demonstrating the significant potential of SSeCAHK as a natural antioxidative functional material for dietary supplementation.

Antiaging Potential of Peptides from Underused Marine Bioresources

Aging is a biological process that occurs under normal conditions and in several chronic degenerative diseases. Bioactive natural peptides have been shown to improve the effects of aging in cell and animal models and in clinical trials. However, few reports delve into the enormous diversity of peptides from marine organisms. This review provides recent information on the antiaging potential of bioactive peptides from underused marine resources, including examples that scavenge free radicals in vitro, inhibit cell apoptosis, prolong the lifespan of fruit flies and Caenorhabditis elegans, suppress aging in mice, and exert protective roles in aging humans. The underlying molecular mechanisms involved, such as upregulation of oxidase activity, inhibition of cell apoptosis and MMP-1 expression, restoring mitochondrial function, and regulating intestinal homeostasis, are also summarized. This work will help highlight the antiaging potential of peptides from underused marine organisms which could be used as antiaging foods and cosmetic ingredients in the near future.

Antioxidant Mechanisms of the Oligopeptides (FWKVV and FMPLH) from Muscle Hydrolysate of Miiuy Croaker against Oxidative Damage of HUVECs

In this work, the antioxidant mechanisms of bioactive oligopeptides (FWKVV and FMPLH) from protein hydrolysate of miiuy croaker muscle against H₂O₂-damaged human umbilical vein endothelial cells (HUVECs) were researched systemically. The finding demonstrated that the HUVEC viability treated with ten antioxidant peptides (M1 to M10) at 100.0 μM for 24 h was not significantly affected compared with that of the normal group (P < 0.05). Furthermore, FWKVV and FMPLH at 100.0 μM could very significantly enhance the viabilities (75.89 ± 1.79% and 70.03 ± 4.37%) of oxidative-damaged HUVECs by H₂O₂ compared with those of the model group (51.66 ± 2.48%) (P < 0.001). The results indicated that FWKVV and FMPLH played their protective functions through increasing the levels of antioxidant enzymes including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreasing the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and nitric oxide (NO) in oxidative-damaged HUVECs in a dose-dependent manner. In addition, the comet assay revealed that FWKVV and FMPLH could dose-dependently protect deoxyribonucleic acid (DNA) from oxidative damage in the HUVEC model. These results suggested that antioxidant pentapeptides (FWKVV and FMPLH) could serve as potential antioxidant additives applied in the food products, pharmaceuticals, and health supplements.

Antioxidant Activity of Novel Casein-Derived Peptides with Microbial Proteases as Characterized via Keap1-Nrf2 Pathway in HepG2 Cells

Casein-derived antioxidant peptides by using microbial proteases have gained increasing attention. Combination of two microbial proteases, Protin SD-NY10 and Protease A "Amano" 2SD, was employed to hydrolyze casein to obtain potential antioxidant peptides that were identified by LCMS/ MS, chemically synthesized and characterized in a oxidatively damaged HepG2 cell model. Four peptides, YQLD, FSDIPNPIGSEN, FSDIPNPIGSE, YFYP were found to possess high 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability. Evaluation with HepG2 cells showed that the 4 peptides at low concentrations (< 1.0 mg/ml) protected the cells against oxidative damage. The 4 peptides exhibited different levels of antioxidant activity by stimulating mRNA and protein expression of the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), as well as nuclear factor erythroid-2-related factor 2 (Nrf2), but decreasing the mRNA expression of Kelch-like ECH-associated protein 1 (Keap1). Furthermore, these peptides decreased production of reactive oxygen species (ROS) and malondialdehyde (MDA), but increased glutathione (GSH) production in HepG2 cells. Therefore, the 4 casein-derived peptides obtained by using microbial proteases exhibited different antioxidant activity by activating the Keap1-Nrf2 signaling pathway, and they could serve as potential antioxidant agents in functional foods or pharmaceutic preparation.

Exploiting of Secondary Raw Materials from Fish Processing Industry as a Source of Bioactive Peptide-Rich Protein Hydrolysates

Developing peptide-based drugs are very promising to address many of the lifestyle mediated diseases which are prevalent in a major portion of the global population. As an alternative to synthetic peptide-based drugs, derived peptides from natural sources have gained a greater attention in the last two decades. Aquatic organisms including plants, fish and shellfish are known as a rich reservoir of parent protein molecules which can offer novel sequences of amino acids in peptides, having unique bio-functional properties upon hydrolyzing with proteases from different sources. However, rather than exploiting fish and shellfish stocks which are already under pressure due to overexploitation, the processing discards, regarded as secondary raw material, could be a potential choice for peptide based therapeutic development strategies. In this connection, we have attempted to review the scientific reports in this area of research that deal with some of the well-established bioactive properties, such as antihypertensive, anti-oxidative, anti-coagulative, antibacterial and anticarcinogenic properties, with reference to the type of enzymes, substrate used, degree of particular bio-functionality, mechanism, and wherever possible, the active amino acid sequences in peptides. Many of the studies have been conducted on hydrolysate (crude mixture of peptides) enriched with low molecular bioactive peptides. In vitro and in vivo experiments on the potency of bioactive peptides to modulate the human physiological functions beneficially have demonstrated that these peptides can be used in the prevention and treatment of non-communicable lifestyle mediated diseases. The information synthesized under this review could serve as a point of reference to drive further research on and development of functionally active therapeutic natural peptides. Availability of such scientific information is expected to open up new zones of investigation for adding value to underutilized secondary raw materials, which in turn paves the way for sustainability in fish processing. However, there are significant challenges ahead in exploring the fish waste as a source of bioactive peptides, as it demands more studies on mechanisms and structure–function relationship understanding as well as clearance from regulatory and statutory bodies before reaching the end user in the form of supplement or therapeutics.

Bioactive peptides from fisheries residues: A review of use of papain in proteolysis reactions

Papain is a cysteine endopeptidase of vegetal origin (papaya (Carica papaya L.) with diverse applications in food technology. In this review we have focused our attention on its application in the production of bio-peptides by hydrolysis of proteins from fish residues. This way, a residual material, that can become a contaminant if dumped without control, is converted into highly interesting products. The main bioactivity of the produced peptides is their antioxidant activity, followed by their nutritional and functional activities, but peptides with many other bioactivities have been produced. Thera are also examples of production of hydrolysates with several bioactivities. The enzyme may be used alone, or in combination with other enzymes to increase the degree of hydrolysis.

Oral delivery of self-assembling bioactive peptides to target gastrointestinal tract disease

Peptides are known for their diverse bioactivities including antioxidant, antimicrobial, and anticancer activity, all three of which are potentially useful in treating colon-associated diseases. Beside their capability to stimulate positive health effects once released in the body, peptides are able to form useful nanostructures such as hydrogels. Combining peptide bioactivity and peptide gel-forming potentials can create interesting systems that can be used for oral delivery. This combination, acting as a two-in-one system, has the potential to avoid the need for delicate entrapment of a drug or natural bioactive compound. We here review the context and research progress, to date, in this area.

Effect of Fish Bone Bioactive Peptides on Oxidative, Inflammatory and Pigmentation Processes Triggered by UVB Irradiation in Skin Cells

In the present study, we evaluated for the first time the photoprotective effect of fish bone bioactive peptides (FBBP) preparation isolated from silver carp (Hypophthalmichthys molitrix) discarded tissue using in vitro experimental models of skin cells exposed to ultraviolet B (UVB) irradiation and stressing agents. FBBP preparation was obtained by papain treatment of minced bones and centrifugal ultrafiltration, and the molecular weight (MW) distribution was characterized by size exclusion and reversed-phase high performance liquid chromatography (RP-HPLC). In vitro assessment of the effect of FBBP pretreatment in UVB-irradiated L929 fibroblasts and HaCaT keratinocytes revealed their cytoprotective activity. Their capacity to efficiently reduce reactive oxygen species (ROS) production and lipid peroxidation varied in a dose-dependent manner, and it was greater in fibroblasts. A decrease of proinflammatory cytokines secretion, in particular of tumor necrosis factor alpha (TNF-α), was found after FBBP pretreatment of THP-1-derived inflamed macrophages. Melanin production and tyrosinase activity investigated in UVB-irradiated Mel-Juso cells were lowered in direct relation to FBBP concentrations. FBBP fractions with high radical scavenging activity were separated by ion exchange chromatography, and two collagenic sequences were identified. All these results offer new scientific data on aquaculture fish bone-derived peptides confirming their ability to control the antioxidant, anti-inflammatory and pigmentation processes developed during UV irradiation of skin cells and recommend their use as valuable natural ingredients of photoprotective cosmeceutical products.

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.

A Review on Health-Promoting, Biological, and Functional Aspects of Bioactive Peptides in Food Applications

Food-derived bioactive peptides are being used as important functional ingredients for health-promoting foods and nutraceuticals in recent times in order to prevent and manage several diseases thanks to their biological activities. Bioactive peptides are specific protein fractions, which show broad applications in cosmetics, food additives, nutraceuticals, and pharmaceuticals as antimicrobial, antioxidant, antithrombotic, and angiotensin-I-converting enzyme (ACE)-inhibitory ingredients. These peptides can preserve consumer health by retarding chronic diseases owing to modulation or improvement of the physiological functions of human body. They can also affect functional characteristics of different foods such as dairy products, fermented beverages, and plant and marine proteins. This manuscript reviews different aspects of bioactive peptides concerning their biological (antihypertensive, antioxidative, antiobesity, and hypocholesterolemic) and functional (water holding capacity, solubility, emulsifying, and foaming) properties. Moreover, the properties of several bioactive peptides extracted from different foods as potential ingredients to formulate health promoting foods are described. Thus, multifunctional properties of bioactive peptides provide the possibility to formulate or develop novel healthy food products.

Can be marine bioactive peptides (MBAs) lead the future of foodomics for human health?

Marine organisms are considered a cache of biologically active metabolites with pharmaceutical, functional, and nutraceutical properties. Among these, marine bioactive peptides (MBAs) present in diverse marine species (fish, sponges, cyanobacteria, fungi, ascidians, seaweeds, & mollusks) have acquired attention owing to their broad-spectrum health-promoting benefits. Nowadays, scientists are keener exploring marine bioactive peptides precisely due to their unique structural and biological properties. These MBAs have reported ameliorating potential against different diseases like hypertension, diabetes, obesity, HIV, cancer, oxidation, and inflammation. Furthermore, MBAs isolated from various marine organisms may also have a beneficial role in the cosmetic, nutraceutical, and food industries. Few marine peptides and their derivative are approved for commercial use, while many MBAs are in various pre-clinical and clinical trials. This review mainly focuses on the diversity of marine bioactive peptides in marine organisms and their production procedures, such as chemical and enzymatic hydrolysis. Moreover, MBAs' therapeutic and biological potential has also been critically discussed herein, along with their status in drug discovery, pre-clinical and clinical trials.

Fractionation of Tilapia By-Product Protein Hydrolysate Using Multilayer Configuration of Ultrafiltration Membrane

Production of small-sized peptides is significant because of their health benefits. Ultrafiltration (UF) membrane provides an effective fractionation of small-sized peptides on a large scale. Thus, the present study was aimed to evaluate the performance of multilayer UF membrane in fractionating tilapia fish by-product (TB) protein hydrolysate by observing the permeate flux, peptide transmission, and peptide distribution under different stirring speed, pH of feed solution, and salt concentration (NaCl). The fractionation process was carried out using a dead-end UF membrane system that consists of a stack of two membrane sheets with different (10/5 kDa) and similar (5/5 kDa) pore sizes in one device. The highest permeate flux (10/5 kDa–39.5 to 47.3 L/m2.h; 5/5 kDa– 15.8 to 20.3 L/m2.h) and peptide transmission (10/5 kDa–51.8 to 61.0%; 5/5 kDa–18.3 to 23.3%) for both multilayer membrane configurations were obtained at 3.0 bar, 600 rpm, pH 8, and without the addition of salt. It was also found that the permeates were enriched with small-size peptides (<500 Da) with a concentration of 0.58 g/L (10/5 kDa) and 0.65 g/L (5/5 kDa) as compared to large-sized peptides (500–1500 Da) with concentration of 0.56 g/L (10/5 kDa) and 0.36 g/L (5/5 kDa). This might indicate the enrichment of small-size peptides through the multilayer membrane which could potentially enhance the biological activity of the protein hydrolysate fraction.

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.

Antioxidant properties of peptides obtained from the split gill mushroom (Schizophyllum commune)

This study sought to assess the ideal conditions under which hydrolysate can be produced from the split gill mushroom proteins through the microbial protease, Alcalase. The research employed a central composite design and response surface methodology. Three specific parameters were varied for the purposes of the experimental process, while a fixed pH value of 8 was used in all cases. The variables were hydrolysis temperature (set as 45 °C, 50 °C, or 55 °C), hydrolysis time (set as 60 min, 120 min, or 180 min), and the ratio of enzyme to substrate (set as 2%, 4%, or 6% w/v). The variables under investigation exert a significant influence upon degree of hydrolysis (DH) in addition to 2,2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity (p < 0.05). Fractionation of the hydrolysate was accomplished using molecular weight (MW) cut-off membranes, while the greatest radical-scavenging capability was observed in the < 0.65 kDa fraction. The MW < 0.65 kDa fraction underwent separation through RP-HPLC in order to create five sub-fractions. Among these, the greatest ABTS radical-scavenging capability was observed in the F₅ sub-fraction, which was therefore chosen to undergo additional examination using quadrupole-time-of-flight-electron spin induction-mass spectrometry-based de novo peptide sequencing. Via this process it was possible to determine five antioxidant peptides. Furthermore, the MW < 0.65 kDa fraction was able to demonstrating cellular antioxidant activity in the context of a human intestinal cancer cell line (HT-29). The extent of this activity was shown to depend upon the concentration levels of the peptide.

Antioxidant potential and physicochemical properties of protein hydrolysates from body parts of North Atlantic sea cucumber (Cucumaria frondosa)

Abstract

Protein hydrolysates were prepared from North Atlantic sea cucumber (Cucumaria frondosa) body wall (BW), and processing by-product flower (FL) and internal organs (IN). Sea cucumber proteins from these three tissues were hydrolysed with selected endopeptidases and exopeptidases. The enzymes used were Alcalase (A), and Corolase (C) as endopeptidases and Flavourzyme (F) with both endo- and exopeptidase functions. These were employed individually or in combination under controlled conditions. The hydrolysates so prepared were subsequently analysed for their antioxidant potential and functionalities in food systems for the first time. Hydrolysates treated with the combination of A and F exhibited the highest radical scavenging activity against DPPH and ABTS radicals. The highest metal chelation activity was observed for samples hydrolysed with the combination of enzymes (C + F and A + F). All treatments inhibited beta-carotene bleaching in an oil-in-water emulsion and TBARS production in a meat model system. In addition, sea cucumber protein hydrolysates were more than 75% soluble over a pH range of 2–12. Hydrolysed proteins were also effective in enhancing water holding capacity in a meat model system compared to their untreated counterparts. The amino acids of sea cucumber protein hydrolysates had desirable profiles with glutamic acid as the predominant component in samples analysed. These findings demonstrate the desirable functionalities of hydrolysates from North Atlantic sea cucumber and their potential for use as functional food ingredients.

Graphical abstract

Functional and Bioactive Properties of Peptides Derived from Marine Side Streams

In fish processing, a great amount of side streams, including skin, bones, heads and viscera, is wasted or downgraded as feed on a daily basis. These side streams are rich sources of bioactive nitrogenous compounds and protein, which can be converted into peptides through enzymatic hydrolysis as well as bacterial fermentation. Peptides are short or long chains of amino acids differing in structure and molecular weight. They can be considered as biologically active as they can contribute to physiological functions in organisms with applications in the food and pharmaceutical industries. In the food industry, such bioactive peptides can be used as preservatives or antioxidants to prevent food spoilage. Furthermore, peptides contain several functional qualities that can be exploited as tools in modifying food ingredient solubility, water-holding and fat-binding capacity and gel formation. In the pharmaceutical industry, peptides can be used as antioxidants, but also as antihypertensive, anticoagulant and immunomodulatory compounds, amongst other functions. On the basis of their properties, peptides can thus be used in the development of functional foods and nutraceuticals. This review focuses on the bioactive peptides derived from seafood side streams and discusses their technological properties, biological activities and applications.

In vitro antioxidant and antihypertensive properties of sesame seed enzymatic protein hydrolysate and ultrafiltration peptide fractions

The objective of this study was to determine the in vitro antioxidant and antihypertensive potentials of sesame seed protein hydrolysate and its membrane ultrafiltration peptide fractions in comparison to the unhydrolyzed protein. Sesame seed protein isolate (SESPI) was prepared from the defatted sesame seed meal and then hydrolyzed using consecutive additions of pepsin and pancreatin to yield sesame protein hydrolysate (SESPH). The SESPH was subjected to membrane ultrafiltration consecutively to obtain fractions with peptide sizes of <1, 1-3, 3-5, and 5-10 kDa, respectively, which were then assayed for in vitro antioxidant and antihypertensive properties. The results showed that protein hydrolysis and fractionation led to significant (p < .05) increases in the content of hydrophobic amino acids. Radical scavenging and metal ion chelation were also significantly (p < .05) enhanced by these treatments. Inhibition of linoleic acid oxidation was stronger with the 1.0 mg/ml of sesame peptide samples in comparison to the mild inhibitory effect exhibited by the 0.5 mg/ml of samples. The <1 kDa peptide fraction was the most active inhibitor (81%) against angiotensin converting enzyme, whereas the bigger peptides (>3-5 and 5-10 kDa) were the most effective (75%-85% ) inhibitors against renin. These sesame products could be used as therapeutic agents in the development of health enhancing foods for the prevention and management of chronic diseases. PRACTICAL APPLICATIONS: Bioactive peptides have been produced from plant protein sources through in vitro enzymatic activities. Sesame seed peptides have demonstrated multifunctional potential to act as antioxidative and antihypertensive agents that could be utilized as ingredients for the development of novel functional foods and nutraceuticals.

Optimization of flaxseed milk fermentation for the production of functional peptides and estimation of their bioactivities

Bioactive peptides are protein fragments which have a positive impact on the functions and conditions of living organisms. Apart from other animal and plant sources flaxseed is an excellent source of bioactive peptides. In recent years, fermentation has been explored as effective way for bioactive peptides generation. Hence, the present study has been carried out to evaluate an indigenous Lactobacillus plantarum strain NCDC 374 for fermentation and peptides generation in flaxseed milk. Optimization of fermentation condition to obtain maximum functional properties (Proteolytic activity, Antioxidant activity and ACE inhibition %) was investigated using response surface methodology. Optimal condition to produce the functional peptides were found to be 4.20% inoculum size with 126 hours of fermentation time. The fermented milk resulted in 67.38% inhibition in DPPH, 41.35% inhibition in ACE and 30.38 micro gram leucine/ml proteolytic activity. Molecular weight cut off membrane (Viva spin) were used to fractionate the peptides. 10 kDa peptides showed optimal results for % DPPH inhibition, ACE inhibition, Antimicrobial activity and DPP-IV inhibition as compared to 5 kDa.

Macrophage-stimulating activity of European eel (Anguilla anguilla) peptides in RAW264.7 cells mediated via NF-κB and MAPK signaling pathways

European eel (Anguilla anguilla) is considered to be a vital commercial fish species. In this study, the effect and molecular mechanism of bioactive peptides from European eel on macrophage-stimulating activity in RAW264.7 cells were investigated. Eel peptide (EP) markedly induced NO and iNOS production and promoted TNF-α and IL-6 secretion in a concentration-dependent manner. Moreover, EP dose-dependently activated NF-κB and MAPK signaling pathways in RAW264.7 cells. In addition, EP was purified using a Sephadex A-25 column and a Bio-Gel P-6 column, and the fraction (Fr-1-1) showing the strongest NO-inducing activity was obtained. Then, the molecular weights of the components in Fr-1-1 were analyzed by LC-MS/MS and found to range from 700 to 1900 Da for the majority of components, which suggested that Fr-1-1 mainly consisted of peptides containing 8-20 amino acid residues. Overall, our results indicated that EP from Anguilla anguilla activated macrophages and could be used as a potential nutraceutical or pharmaceutical.

Purification and identification of novel antioxidant peptides from silver carp muscle hydrolysate after simulated gastrointestinal digestion and transepithelial transport

Unregulated oxidative reactions occur in human body or food system can cause harmful effects both on food quality and human health. This study aimed to develop novel antioxidant peptides from silver carp muscle hydrolysate after simulated gastrointestinal digestion and transepithelial transport. Results showed that alcalase- and papain-induced hydrolysates had higher antioxidant activities before and after in vitro gastrointestinal digestion. Fractions with molecular weight <1 kDa from these two digestive products (named A-GID-1 and P-GID-1) exhibited the greatest antioxidant capacity, which was ascribed to the large proportion of low-molecular peptides and hydrophobic amino acids. After transepithelial transport analysis, a total of ten peptides were identified from the RP-HPLC fractions with the highest antioxidant activity from both P-GID-1 and A-GID-1 permeates. Among them, LVPVAVF exhibited the highest DPPH radical scavenging and reactive oxygen species (ROS) inhibitory activity. Our findings will provide new knowledge for the development of novel natural antioxidants and the high-value utilization of silver carp protein.

Anti-inflammatory action of two novel peptides derived from peanut worms (Sipunculus nudus) in lipopolysaccharide-induced RAW264.7 macrophages

Peanut worm (Sipunculus nudus Linn.) protein was hydrolyzed by three proteases, and NO scavenging activity of the protein hydrolysates was evaluated. The hydrolysate obtained using Alcalase® showed the highest NO scavenging activity. This hydrolysate was fractionated using 10-, 5-, and 3 kDa molecular weight cut-off membranes, and the lowest MW fraction (<3 kDa) exhibited the highest NO scavenging activity. The <3 kDa fraction was further purified by gel filtration and high-performance liquid chromatographies. The peptides in the HPLC fraction with the strongest anti-NO activity were identified by quadrupole-time-of-flight mass spectrometry as LSPLLAAH (821.48 Da) and TVNLAYY (843.42 Da). Both peptides and the corresponding pure synthetic peptides inhibited NO production by RAW 264.7 macrophages without cytotoxicity. Quantitative real-time RT-PCR analysis showed that peptides LSPLLAAH and TVNLAYY reduced expression of proinflammatory cytokine genes iNOS, IL-6, TNF-α, and COX-2 in RAW 264.7 macrophages, suggesting that these peptides are novel anti-inflammatory candidates.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.