Contribution of specific amino acid and secondary structure to the antioxidant property of corn gluten proteins

Plant-based antioxidant peptides: impact on oxidative stress and gut microbiota

Plant-based peptides can be obtained from natural and climate-friendly sources. These peptides show various bioactivities including antioxidant activity. Oxidative stress has an impact on the gut microbiota causing inflammation, insulin resistance, osteoporosis, cancer, and several chronic diseases like type 2 diabetes, arthritis, hypertension, and atherosclerosis. Therefore, antioxidant peptides may significantly affect oxidative stress as a potential alternative to conventional medication. The production of antioxidant peptides from plant-based protein sources through conventional and innovative approaches may provide promising strategies to improve gut microbiota. Recent studies in plant-based antioxidant peptides (PBAP) focus on their advanced identification and characterization techniques, structure-activity relationship, improvement of extraction and purification, cellular and molecular mechanisms, specific health applications in preventing and managing conditions with gut microbiota, and commercial applications in nutraceuticals. Short-chain fatty acids and reactive sulfur species are specific gut-derived metabolites that can improve metabolic function by modulating oxidative stress and the immune system. This review highlights the influence of food oxidants on the gut microbiota and PBAP-induced modulation of gut microbiota. Moreover, the production of PBAP and the challenges in their application will be discussed.

Physicochemical Properties and Stability of Antioxidant Peptides from Swim Bladder of Grass Carp (Ctenopharyngodon idella)

Grass carp swim bladder collagen peptides (GCPs) were purified by ultrafiltration and Sephadex G-15 chromatography to obtain GCP-II, which exhibited superior antioxidant activity. GCP-II exhibited 78.22% ABTS+ scavenging activity and 72.91% Fe2⁺ chelating activity, along with around 90% thermal stability between 4 °C and 100 °C. Environmental factors such as 4% NaCl reduced superoxide scavenging to 59.16% of the original and 0.2% citric acid reduced it to 71.57% of the original, while glucose showed minimal impact on the antioxidant activity of GCP-II. From 464 GCP-II sequences analyzed via LC-MS/MS, 7 bioactive peptides were selected based on antioxidant activity and functional sequence motifs, and were named peptides 1 to 7, respectively. These peptides were synthesized through solid-phase methods, validated for purity exceeding 95% using HPLC and mass spectrometry, and tested for antioxidant performance. Peptides 1, 3, 6, and 7 demonstrated notable antioxidant efficacy: peptide 6 showed 63.31% ABTS+ scavenging activity at 1 mg/mL, while peptides 3 and 6 exhibited synergistic effects in DPPH and hydroxyl radical scavenging experiments, surpassing theoretical values by 0.88% and 2.16%, respectively. This study underscores the potential of synthetic GCPs and GCP-II-derived peptides as functional antioxidants, particularly peptide 3 and peptide 6.

Antioxidant potential of peptides derived from chia seeds (Salvia hispanica L.) as natural preservatives

The challenge of preserving food quality without relying on harmful antioxidants requires the exploration of natural alternatives, such as chia-derived peptides (YACLKVK, KLKKNL, KLLKKYL, and KKLLKI). The antioxidant properties and stability to processing were evaluated using DPPH and ABTS, iron-reducing, ORAC, and copper chelating assays. The effects of autoclaving, heat treatment with glucose, and ultrasound on the antioxidant activity of the top-performing peptide were examined. YACLKVK displayed the highest antioxidant response with 87.25 ± 2.47 %, 93.65 ± 0.79 %, 0.418 ± 0.018 abs, 44.06 ± 0.78 μM TE/mL, and 86.49 ± 0.12 % in the DPPH, ABTS, iron-reducing capacity, ORAC, and copper chelating assays at 800 μg/mL (DPPH) and 1000 μg/mL, respectively. Autoclaving, heat, and ultrasound treatments reduced YACLKVK's DPPH scavenging to 63.09 ± 0.44 % and 74.15 ± 0.27 % and its Cu chelating capacity to 58.98 ± 1.28 %. YACLKVK retained over 50 % of its antioxidant capacity post-processing. These findings suggest its application as a potent natural antioxidant in food systems, particularly in processed foods where oxidation affects shelf life and quality. Incorporating YACLKVK could enhance food preservation, aligning with consumer preferences for natural-origin ingredients. Studies on commercial scalability, safety, and regulatory compliance will be essential for its widespread adoption in the food industry.

Biologically Active Peptides from Corn Gluten Meal Improve Microbiota Disorders Caused by Helicobacter pylori Infection in Mice

This study investigated the potential effects of corn protein activity peptides (CPAPs) on inflammation response levels and gastrointestinal microbiota in Helicobacter pylori (H. pylori) infection mice. CPAPs significantly up-regulated the mRNA expression of the anti-inflammatory factor IL-10 and down-regulated the mRNA expression of the pro-inflammatory factors TGF-β, TLR4, MyD88, and NF-κB, indicating that CPAPs may antagonize H. pylori-induced inflammatory responses by inhibiting NF-κB signaling pathways. Through the intervention of CPAPs, H. pylori colonization in the stomach was significantly reduced. Additionally, the structural composition of the gastrointestinal microbiota improved, with an increase in abundance and diversity. These changes positively regulate gastrointestinal microbiota disorders in mice. In addition, the PICRUST function prediction of intestinal microbiota revealed that CPAPs may prevent or reduce metabolic disorders brought about by H. pylori, which improve biometabolic pathways by modulating intestinal microbiota composition. In conclusion, these findings suggest that CPAPs may prevent or mitigate metabolic disorders induced by H. pylori, offering theoretical support for the development of corn-protein-based functional foods.

In silico identification and experimental validation of two types of angiotensin-converting enzyme (ACE) and xanthine oxidase (XO) milk inhibitory peptides

Bioactive peptides have received significant attention due to their natural origin, low toxicity, and targeting specificity in the past decade. This study identified highly active ACE/XO inhibitors using molecular simulation and online databases and validated their in vitro antioxidant activity and the mechanisms of molecular interactions. According to computer predictions, Asp-Gly-Gly (DGG) and Asp-Gly-Met (DGGM) were identified as potential hydrolysates of common gastrointestinal peptidases with well water-soluble, non-toxic, and non-allergenic. Fourier transform infrared spectroscopy showed that the two peptides altered the enzyme's secondary structure, decreasing α-helix content by about 13 %, along with increasing β-sheet, randam coli, and β-turns content. Molecular docking and molecular dynamics simulations showed that hydrogen bonding and electrostatic interactions caused DGG and DGGM to form stable and dense complexes with the two enzymes. This study provides a new way for economical and efficient screening of new ACE and XO inhibitory peptides from natural proteins.

Peptide Profile Changes in Buffalo Milk Cheese during Different Storage Periods and Characterization of Novel Bioactive Peptides through Peptidomics

This study aimed to investigate the changes in the bioactive peptides (BPs) of buffalo milk cheese (BMC) within 15 days of storage. A total of 3605 peptides were identified in the BMC, with 260 peptides remaining stable for 15 days. Among these, the peak intensities of all reported BPs (9 peptides) increased on the 15th day. Additionally, two novel antioxidant peptides, AYF (IC50 = 160.5 μM) and YPFPGPIPK (IC50 = 108.6 μM), and two novel angiotensin-converting enzyme (ACE) inhibitory peptides, LRF (IC50 = 214.9 μM) and APFPEVFGK (IC50 = 880.0 μM), were identified. The molecular docking results implied that the active sites on ECH-associated protein 1 (Arg 415, Arg 483, Arg 380, and Asn 382) and the active sites in the three active pockets of ACE (S1, S2, and S'1) are crucial for peptide activity. This study demonstrates that BMC is a stable resource of BPs and has the potential to be used in functional foods.

Study on the antioxidant and antiosteoporotic activities of the oyster peptides prepared by ultrasound-assisted enzymatic hydrolysis

In this study, the effects of ultrasound-assisted enzymatic hydrolysis on the production of antioxidant and antiosteoporotic peptides derived from oysters were investigated. Results showed that ultrasound-assisted enzymatic hydrolysis significantly enhanced the peptide content, free radical scavenging ability, and ferric reducing antioxidant power of total oyster protein hydrolysate (TOPH), with optimal results achieved at 200 W (TOPH-200). Correspondingly, ultrasound treatment at 200 W increased the exposure of hydrophobic regions, reduced α-helix content, and facilitated the generation of small molecular weight peptides in TOPH. In an H2O2-induced oxidative damage model of osteoblastic MC3T3-E1 cells, TOPH-200 significantly attenuated intracellular reactive oxygen species and improved mitochondrial membrane potential. Importantly, TOPH-200 effectively enhanced osteogenic cell proliferation, differentiation, and mineralization in H2O2-treated MC3T3-E1 cells. Additionally, two novel peptides, DSQLAPFRF and HFNPRL, were screened from the TOPH-200 using PeptideRanker and molecular docking. Further cell experiments indicated that both peptides exhibited potent antioxidant and antiosteoporotic activities in oxidatively damaged MC3T3-E1 cells. In summary, mild ultrasound-assisted enzymatic hydrolysis proved effective in producing bioactive peptides from oysters, and these newly identified peptides exhibit potential for osteoporosis prevention.

Antioxidative and mineral-binding food-derived peptides: Production, functions, metal complexation conditions, and digestive fate

The discovery of food-derived biopeptides is becoming increasingly prevalent in the scientific community. Some peptides possess multiple biological functions that can confer health benefits through various mechanisms following ingestion. The present review targets food-derived antioxidant and mineral-binding peptides (AMBPs) including their production procedure i.e., enzymolysis, separation, and purification (through membrane separation, gel filtration, ion exchange chromatography, and high-performance liquid chromatography), followed by mass spectrometry for identification. The most effective AMBPs exhibit radical scavenging activity, detoxification of excess metals, and reduction of lipid peroxidation to facilitate mineral bioavailability. The metal complexation of AMBPs necessitates an optimal metal-to-peptide ratio, specific ligands, precursors, and complexation reactions. The bioavailability and absorbability mechanisms of AMBPs are also elucidated, encompassing gastrointestinal stability, binding mode, and cell absorption machinery. Ultimately, further considerations regarding additional research on AMBPs are provided, which will assist researchers in conducting more comprehensive studies to promote the effective and safe use of AMBPs.

Extraction, purification, and mechanism of immunomodulatory peptides obtained from silkworm pupa protein hydrolysate

Silkworm pupa, a by-product of silk reeling, is rich in protein; however, it has traditionally been used as animal feed. This study isolated and purified peptides from the enzymatic hydrolysates of silkworm pupa protein, thus effectively enhancing its utilization. The immune activity of these peptides was evaluated in macrophages, and 609 peptides were identified using LC-MS/MS. These active peptides were screened based on their toxicity, allergenic, and biological activity, and their interactions with TLR2 and TLR4/MD-2 were predicted via molecular docking. Results indicated that APFAPAPL, YLPPFNSF, and FIPNEAFAGRPF could strongly bind to TLR2 and TLR4/MD-2 through hydrogen bonding and hydrophobic interactions. These peptides were synthesized using solid-phase synthesis, and their immune activity was verified by proliferation, NO, ROS and TNF-α secretion assays. All three peptides promoted the proliferation, phagocytosis, and secretion of ROS and TNF-α by macrophages. Western blot analysis showed that the peptides activated RAW 264.7 cells via the NF-κB and MAPK signaling pathways, mediated by TLR2 and TLR4/MD-2 receptors. Therefore, this study provides a new understanding of the immunomodulatory activity of silkworm pupa proteins, implying their potential use as functional food ingredients.

Lipidomics and metabolomics reveal the molecular mechanisms underlying the effect of thermal treatment on composition and oxidative stability of walnut oil

Roasting walnut kernel significantly improves the oxidative stability and sensory properties of its oil. However, the effect of roasting temperatures on the molecular change of main components and micronutrients in walnut oil is still unclear. Herein, lipidomics and metabolomics were integrated to comprehensively profile the walnut oil obtained at different roasting temperatures (30 °C, 120 °C, 140 °C, 160 °C, and 180 °C). Lipidomics showed that the content of glycerolipids, sphingolipids, and glycerophospholipids decreased with roasting temperatures, while the oxidized fatty acids and triglycerides increased. Ratios of linoleic acid and linolenic acid varied with roasting temperatures and were most close to 4-6:1 at 140 °C, 160 °C, and 180 °C. Major classes of micronutrients showed a tendency to increase at the roasting temperature of 120 °C and 140 °C, then decrease at 160 °C and 180 °C. Liposoluble amino acids identified for the first time in walnut oil varied with roasting temperatures. Correlation analysis demonstrated that the higher contents of liposoluble amino acids and phenolics are positively associated with enhanced oxidative stability of walnut oil obtained at 140 °C. Furthermore, glutamine and 5-oxo-D-proline were expected to be potential biomarkers to differentiate the fresh and roasted walnut oil. The study is expected to provide new insight into the change mechanism of both major lipids and micronutrients in walnut oil during the roasting process.

Structural characterization of peroxyl radical oxidative products of antioxidant peptides from hydrolyzed proteins

This work aimed to characterize oxidative products of five unique antioxidant peptides (P1: YFDEQNEQFR, P2: GQLLIVPQ, P3: SPFWNINAH, P4: NINAHSVVY, P5: RALPIDVL) from hydrolyzed oat proteins. Peptides were reacted with 2,2'-Azobis(2-amidinopropane) dihydrochloride, a common peroxyl radical generator. Chromatographic data showed that peptide P3 was the most oxidized (67 ± 4 %) while also displaying the most ability to scavenge radicals in the oxygen absorbance capacity assay (ORAC) with an activity of 2.16 ± 0.09 μM Trolox equivalents/μM peptide. Structural characterization using mass spectrometry showed the presence of four oxidative products of P3, three of which were mono-oxygenated and the fourth di-oxygenated. The identification of these oxidative products is new and provides an opportunity to investigate their biological function. A good correlation (r = 0.889) between the degree of oxidation and the ORAC data, demonstrates the usefulness of using oxidative peptide data to predict their radical scavenging activities.

Effect of high hydrostatic pressure treatment on the antioxidant activity of lactoferrin before and after gastrointestinal digestion

In this study, high hydrostatic pressure treatment of lactoferrin was used to investigate its effect on the hydrolysis and antioxidant activity of lactoferrin. The results showed that high hydrostatic pressure treatment at 600 MPa increased the exposure level of tryptophan residues of lactoferrin by 82.29%, which significantly altered the tertiary structure of lactoferrin, and this change was observed in scanning electron microscopy as an increase in the contact area of lactoferrin that could be contacted by proteases. Pressure treatments of 400 MPa and above increased the hydrolysis of lactoferrin for gastrointestinal digestion by 21.19%, which increased the release of antioxidant-related amino acids and increased the free radical scavenging capacity of lactoferrin intestinal digestive fluid by 35.12%. Meanwhile, two lactoferrin antioxidant peptides, QAYPNLCQLCK and NCPDKFCLFK, were identified in the lactoferrin intestine digest. These findings indicate that high hydrostatic pressure treatment could be a potentially beneficial method for processing lactoferrin.

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.

Plant Protein-Derived Active Peptides: A Comprehensive Review

Active peptides are a class of physiologically active protein fragments, which can be prepared from different sources. In the past few decades, the production of peptides with various effects from different plant proteins continues to receive academic attention. With advances in extraction, purification, and characterization techniques, plant protein-derived active peptides continue to be discovered. They have been proven to have various functional activities such as antioxidant, antihypertensive, immunomodulatory, antimicrobial, anti-inflammatory, antidiabetic, antithrombotic, and so on. In this review, we searched Web of Science and China National Knowledge Infrastructure for relevant articles published in recent years. There are 184 articles included in this manuscript. The current status of plant protein-derived active peptides is systematically introduced, including their sources, preparation, purification and identification methods, physiological activities, and applications in the food industry. Special emphasis has been placed on the problems of active peptide exploration and the future trend. Based on these, it is expected to provide theoretical reference for the further exploitation of plant protein-derived active peptides, and promote the healthy and rapid development of active peptide industry.

Impact of In Vitro Digestion on the Digestibility, Amino Acid Release, and Antioxidant Activity of Amaranth (Amaranthus cruentus L.) and Cañihua (Chenopodium pallidicaule Aellen) Proteins in Caco-2 and HepG2 Cells

This study evaluated the impact of in vitro gastrointestinal digestion on the digestibility, amino acid release, and antioxidant activity of proteins from amaranth (Amarantus cruentus L.) and cañihua (Chenopodium pallidicaule Aellen). Antioxidant activity was assessed using ORAC, ABTS, DPPH, and cellular antioxidant activity (CAA) assays in human intestinal Caco-2 and hepatic Hep-G2 cell lines. The results showed that amaranth had higher protein digestibility (79.19%) than cañihua (71.22%). In addition, intestinal digestion promoted the release of essential amino acids, such as leucine, lysine, and phenylalanine, in both protein concentrates. Concentrations of amaranth and cañihua proteins, ranging from 0.125 to 1.0 mg mL-1, were non-cytotoxic in both cell lines. At a concentration of 0.750 mg mL-1, simulated gastrointestinal digestion enhanced cellular antioxidant activity. Intestinal digest fractions containing peptides >5 kDa were the principal contributors to CAA in both cell lines. Notably, cañihua proteins exhibited high CAA, reaching values of 85.55% and 82.57% in Caco-2 and HepG2 cells, respectively, compared to amaranth proteins, which reached 84.68% in Caco-2 and 81.06% in HepG2 cells. In conclusion, both amaranth and cañihua proteins, after simulated gastrointestinal digestion, showcased high digestibility and released peptides and amino acids with potent antioxidant properties, underscoring their potential health benefits.

Preparation of Corn Peptides with Anti-Adhesive Activity and Its Functionality to Alleviate Gastric Injury Induced by Helicobacter pylori Infection In Vivo

More than 50% of the world population is infected with Helicobacter pylori (H. pylori), which is classified as group I carcinogen by the WHO. H. pylori surface adhesins specifically recognize gastric mucosal epithelial cells' (GES-1 cells) receptor to complete the adhesion. Blocking the adhesion with an anti-adhesion compound is an effective way to prevent H. pylori infection. The present study found that corn protein hydrolysate, hydrolyzed by Neutral, effectively alleviated gastric injury induced by H. pylori infection through anti-adhesive and anti-inflammatory effects in vitro and in vivo. The hydrolysate inhibited H. pylori adhesion to GES-1 cells significantly, and its anti-adhesive activity was 50.44 ± 0.27% at 4 mg/mL, which indicated that the hydrolysate possessed a similar structure to the GES-1 cells' receptor, and exhibited anti-adhesive activity in binding to H. pylori. In vivo, compared with the H. pylori infection model group, the medium and high dose of the hydrolysate (400-600 mg/kg·bw) significantly decreased (p < 0.05) the amount of H. pylori colonization, pro-inflammatory cytokines (IL-6, IL-1β, TNF-α and MPO), chemokines (KC and MCP-1) as well as key metabolites of NF-κB signaling pathway levels (TLR4, MyD88 and NF-κB), and it increased antioxidant enzyme contents (SOD and GSH-Px) and the mitigation of H. pylori-induced pathological changes in the gastric mucosa. Taken together, these results indicated that the hydrolysate intervention can prevent H. pylori-induced gastric injury by anti-adhesive activity and inhibiting the NF-κB signaling pathway's induction of inflammation. Hence, the corn protein hydrolysate might act as a potential anti-adhesive agent to prevent H. pylori infection.

Preparation and identification of a novel peptide with high antioxidant activity from corn gluten meal

The antioxidant activity of corn peptides is related to their molecular weight and structure. Corn gluten meal (CGM) was hydrolyzed using a combination of Alcalase, Flavorzyme and Protamex, and the hydrolysates were subjected to antioxidant activity analysis after further fractionation. Corn peptides with molecular weights less than 1 kDa (CPP1) exhibited excellent antioxidant activity. A novel peptide, Arg-Tyr-Leu-Leu (RYLL), was identified from CPP1. RYLL displayed preferable scavenging capacities for ABTS radicals and DPPH radicals, with IC₅₀ values of 0.122 mg/ml and 0.180 mg/ml, respectively. Based on quantum calculations, RYLL had multiple antioxidant active sites, and tyrosine was the main active site due to the highest energy of the highest occupied molecular orbit (HOMO). Moreover, the simple peptide structure and hydrogen bond network of RYLL contributed to the exposure of the active site. This study elucidated the antioxidant mechanism of corn peptides, which could provide an understanding for CGM hydrolysates as natural antioxidants.

Ultrasound-assisted extraction and characteristics of maize polysaccharides from different sites

Antitumor, antioxidant, hypoglycemic, and immunomodulatory properties are all exhibited by maize polysaccharides. With the increasing sophistication of maize polysaccharide extraction methods, enzymatic method is no longer limited to a single enzyme to extract polysaccharides, and is more often used in combination with ultrasound or microwave, or combination with different enzymes. Ultrasound has a good cell wall-breaking effect, making it easier to dislodge lignin and hemicellulose from the cellulose surface of the maize husk. The "water extraction and alcohol precipitation" method is the simplest but most resource- and time-consuming process. However, the "ultrasound-assisted extraction" and "microwave-assisted extraction" methods not only compensate for the shortcoming, but also increase the extraction rate. Herein, the preparation, structural analysis, and activities of maize polysaccharides were analyzed and discussed.

Nature-Inspired Bioactive Compounds: A Promising Approach for Ferroptosis-Linked Human Diseases?

Ferroptosis is a type of cell death driven by iron overload and lipid peroxidation. It is considered a key mechanism in the development of various diseases such as atherosclerosis, Alzheimer, diabetes, cancer, and renal failure. The redox status of cells, such as the balance between intracellular oxidants (lipid peroxides, reactive oxygen species, free iron ions) and antioxidants (glutathione, glutathione Peroxidase 4), plays a major role in ferroptosis regulation and constitutes its principal biomarkers. Therefore, the induction and inhibition of ferroptosis are promising strategies for disease treatments such as cancer or neurodegenerative and cardiovascular diseases, respectively. Many drugs have been developed to exert ferroptosis-inducing and/or inhibiting reactions, such as erastin and iron-chelating compounds, respectively. In addition, many natural bioactive compounds have significantly contributed to regulating ferroptosis and ferroptosis-induced oxidative stress. Natural bioactive compounds are largely abundant in food and plants and have been for a long time, inspiring the development of various low-toxic therapeutic drugs. Currently, functional bioactive peptides are widely reported for their antioxidant properties and application in human disease treatment. The scientific evidence from biochemical and in vitro tests of these peptides strongly supports the existence of a relationship between their antioxidant properties (such as iron chelation) and ferroptosis regulation. In this review, we answer questions concerning ferroptosis milestones, its importance in physiopathology mechanisms, and its downstream regulatory mechanisms. We also address ferroptosis regulatory natural compounds as well as provide promising thoughts about bioactive peptides.

Characteristics of the Beef Cheek Meat-Based Sausage Added with Snakehead (Channa striata) Gelatin

This study is aimed at determining the functional effect of snakehead fish gelatin as a binder on the characteristics and shelf life of beef cheek-based emulsion sausage compared with bovine commercial gelatin. The level of snakehead fish gelatin used was 0%, 1%, 2%, and 3%, while that of bovine commercial gelatin was 2% with a storage time of 0 to 28 days in the refrigerator (4 ± 2°C). Emulsion stability, cooking loss, proximate composition, texture profile, and microstructure of sausage were initially determined before storage; then, observations were made every seven days to determine the shelf life of sausages based on pH, antioxidant activity, and TBA reactivity. Characteristics such as emulsion stability, proximate composition, and texture profile were influenced by the treatment (p < 0.05). The gelatin level significantly affected the water holding capacity of sausages (p < 0.05), but the storage time did not (p > 0.05). On the other hand, the pH, TBA reactivity, and antioxidant activity of sausages were not only affected by gelatin level (p < 0.05) but also by storage time (p < 0.05). The sausage microstructure confirms the use of 2% snakehead fish gelatin to make sausages with properties similar to 2% commercial bovine gelatin. The byproduct of the snakehead fish industry can be used as a gelatin alternative to produce sausages. This gelatin has the potential as a binder, which can functionally improve sausage characteristics. This effectiveness can boost the water holding capacity of sausages, although it has not been effective in inhibiting fat oxidation which causes an increase in malonaldehyde levels.

Resource Utilization of Bovine Neck Ligament: Enzymatic Preparation of Elastin Peptide and Its Antioxidant Activity

Elastin is considered an excellent resource for obtaining antioxidant peptides due to unique amino acid composition. However, it is hardly soluble in water or in dilute acid or alkali; most of the elastases have low yields for preparing elastin peptides, making it difficult to meet industrial applications. To address above problems, enzymes capable of hydrolyzing elastin into soluble peptides were preferred from typical commercial protease preparations. The optimal enzymatic hydrolysis process conditions for elastin peptides were obtained by response surface optimization design. The molecular weight, amino acid composition, and antioxidant activity of the enzymatic hydrolysis products were determined. The results show that the alkaline protease NUE has a strong hydrolysis effect. The optimized enzymatic hydrolysis conditions are as follows: substrate concentration is 5%, enzyme concentration is 650 U/mL, pH is 10.0, temperature is 60 °C, time is 6 h. The degree of hydrolysis of elastic protein peptides obtained through this method is 14.42%. The distribution of molecular weight is 200-6500 Da, more than 85% of the component molecular amount is greater than 800 Da; the amino acid content related to antioxidant activity has reached 68 mg/100 mg, so it has extremely high free radical clearance. Compared with acid and alkali methods, the anti-oxidation capacity of enzyme-based peptide is better, the reaction conditions are milder, the yield is higher, and by-products and pollutants are fewer. It provides an effective way to industrialized production of elastin peptides with high antioxidant activity and a basis for its widespread application in the food and pharmaceutical industries.

Antioxidant peptides: Overview of production, properties, and applications in food systems

In recent years, several studies have reported the beneficial effects of antioxidant peptides in delaying oxidation reactions. Thus, a growing number of food proteins have been investigated as suitable sources for obtaining these antioxidant peptides. In this study, some of the most critical developments in the discovery of peptidic antioxidants are discussed. Initially, the primary methods to release, purify, and identify these antioxidant peptides from various food-derived sources are reviewed. Then, computer-based screening methods of the available peptides are summarized, and methods to interpret their structure-activity relationship are illustrated. Finally, approaches to the large-scale production of these bioactive peptides are described. In addition, the applications of these antioxidants in food systems are discussed, and gaps, future challenges, and opportunities in this field are highlighted. In conclusion, various food items can be considered promising sources to obtain these novel antioxidant peptides, which present various opportunities for food applications in addition to health promotion. The lack of in-depth data on the link between the structure and activity of these antioxidants, which is critical for the prediction of possible bioactive amino acid sequences and their potency in food systems and in vivo conditions (rather than in vitro systems), requires further attention. Consequently, future collaborative research activities between the industry and academia are required to realize the commercialization objectives of these novel antioxidant peptides.

Food Protein-Derived Antioxidant Peptides: Molecular Mechanism, Stability and Bioavailability

The antioxidant activity of protein-derived peptides was one of the first to be revealed among the more than 50 known peptide bioactivities to date. The exploitation value associated with food-derived antioxidant peptides is mainly attributed to their natural properties and effectiveness as food preservatives and in disease prevention, management, and treatment. An increasing number of antioxidant active peptides have been identified from a variety of renewable sources, including terrestrial and aquatic organisms and their processing by-products. This has important implications for alleviating population pressure, avoiding environmental problems, and promoting a sustainable shift in consumption. To identify such opportunities, we conducted a systematic literature review of recent research advances in food-derived antioxidant peptides, with particular reference to their biological effects, mechanisms, digestive stability, and bioaccessibility. In this review, 515 potentially relevant papers were identified from a preliminary search of the academic databases PubMed, Google Scholar, and Scopus. After removing non-thematic articles, articles without full text, and other quality-related factors, 52 review articles and 122 full research papers remained for analysis and reference. The findings highlighted chemical and biological evidence for a wide range of edible species as a source of precursor proteins for antioxidant-active peptides. Food-derived antioxidant peptides reduce the production of reactive oxygen species, besides activating endogenous antioxidant defense systems in cellular and animal models. The intestinal absorption and metabolism of such peptides were elucidated by using cellular models. Protein hydrolysates (peptides) are promising ingredients with enhanced nutritional, functional, and organoleptic properties of foods, not only as a natural alternative to synthetic antioxidants.

Corn distillers solubles as a novel bioresource of bioactive peptides with ACE and DPP IV inhibition activity: characterization, in silico evaluation, and molecular docking

This study aimed to investigate the biological potential of underutilized and low-value corn distillers solubles, containing a unique unexplored blend of heat-treated corn and yeast proteins, from the bioethanol industries, by bioinformatic and biochemical approaches. Protein hydrolysates were produced by applying four commercially accessible proteases, among which alcalase provided the best results in terms of yield, degree of hydrolysis, molecular weight, number of proteins, bioactive peptides, and deactivation against anti-angiotensin I-converting enzyme (ACE) and anti-dipeptidyl peptidase IV (DPP IV). The optimal conditions to produce anti-ACE and anti-DPP IV peptides were using alcalase for 10.82 h and an enzyme : substrate ratio of 7.90 (%w/w), with inhibition values for ACE and DPP IV of 98.76 ± 1.28% and 34.99 ± 1.44%, respectively. Corn (α-zein) and yeast (glyceraldehyde-3-phosphate dehydrogenase) proteins were mainly suitable, upon enzymolysis, for the release of bioactive peptides. The peptides DPANLPWG, FDFFDNIN, WNGPPGVF, and TPPFHLPPP inhibited ACE more effectively as verified with binding energies of -11.3, -11.6, -10.5, and -11.6 kcal mol^-1, respectively, as compared to captopril (-6.38 kcal mol^-1). Compared with the binding energy of sitagliptin (-8.6 kcal mol^-1), WNGPPGVF (-9.6 kcal mol^-1), WPLPPFG (-9.8 kcal mol^-1), LPPYLPS (-9.7 kcal mol^-1), TPPFHLPPP (-10.1 kcal mol^-1), and DPANLPWG peptides (-10.1 kcal mol^-1) had greater inhibition potential against DPP IV. The peptides impeded ACE and DPP IV majorly via hydrophobic and hydrogen linkage interactions. The key amino acids TYR⁵²³, GLU³⁸⁴, and HIS³⁵³ were bound to the catalytic sites of ACE and GLN⁵⁵³, GLU²⁰⁶, PHE³⁶⁴, VAL³⁰³, and THR³⁰⁴ were bound to the DPP IV enzyme. The PHs can be used as ingredients in the feed or food industries with possible health advantages.

Protein Hydrolysates Derived from Animals and Plants—A Review of Production Methods and Antioxidant Activity

There is currently considerable interest on the use of animal, plant, and fungal sources in the production of bioactive peptides, as evidenced by the substantial body of research on the topic. Such sources provide cheap and environmentally friendly material as it often includes waste and by-products. Enzymatic hydrolysis is considered an efficient method of obtaining peptides capable of antioxidant activity. Those properties have been proven in terms of radical-scavenging capacity using the DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2-azinobis-(3-ethyl-benzothiazoline-6-sulphonic acid)), hydroxyl and superoxide radical methods. Additionally, the reducing power, ferrous ion-chelating (FIC), ferric reducing antioxidant power (FRAP), and the ability of the protein hydrolysates to inhibit lipid peroxidation have also been explored. The results collected in this review clearly indicate that the substrate properties, as well as the conditions under which the hydrolysis reaction is carried out, affect the final antioxidant potential of the obtained peptides. This is mainly due to the structural properties of the obtained compounds such as size or amino acid sequences.

Characterization of a synergistic antioxidant synthetic peptide from sea cucumber and pine nut

We compared antioxidant activity of the synthetic peptide Val-Leu-Leu-Tyr-Gln-Asp-His-Cys-His (VLLYQDHCH), sea cucumber peptide Val-Leu-Leu-Tyr (VLLY) and pine seed peptide Gln-Asp-His-Cys-His (QDHCH). The structure-activity relationship was analyzed based on radical scavenging ability and Raman, circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR). Based on RP-HPLC, the contents of peptides in simulated gastrointestinal tract and digestive juices in rat intestinal sac were determined, and their absorption stability were explored. These results showed that the DPPH clearance rate of VLLYQDHCH was 45.90% higher than the sum of VLLY and QDHCH at 3 mmol/L. The α-helix, β-sheet and random coil of VLLYQDHCH increased, β-turn decreased, and the active hydrogen site shifted. After simulated digestion and absorption, the retention rate of VLLYQDHCH was 80.86 ± 0.88% in simulated stomach and 45.75 ± 0.97% in simulated intestine. There was no significant difference in the absorption rates of the three peptides (P > 0.05). This research provided a new idea for the development of safe and green food-derived animal-plant protein antioxidant peptides.

Graphic abstract

Screening and bioavailability evaluation of anti-oxidative selenium-containing peptides from soybeans based on specific structures

Our previous study has evaluated the antioxidant capacity and identified the sequences of soybean selenium-containing peptides. Herein, pharmacophore screening, gastrointestinal simulation and in vivo pharmacokinetics were performed to predict the potentials of selenium-containing peptides in terms of antioxidant activity, safety and bioavailability. A pharmacophore model with 6 structure features was constructed for virtual screening to determine the potential activities of 85 selenium sequences from soybean peptides. Strong reversing effects (p < 0.05) of the targeted sequences were observed in tumor necrosis factor-α (TNF-α)-induced inflammatory cytokines and adhesion factors burst in EA·hy926/Caco-2 co-culture cell models. Ser-Phe-Gln-SeMet (SFQSeM), a promising peptide selected from both virtual screening and cell models, was proved to be stable in the gastrointestinal tract and could be transported across the Caco-2 monolayer via the paracellular pathway. Additionally, SFQSeM showed a long residence time (89.42 ± 1.34 min) and half-life (81.60 ± 11.88 min) after consumption, and it induced lower liver alanine/aspartate transaminase (ALT/AST) and serum nitric oxide (NO) levels compared to Na2SeO3 and SeMet (p < 0.05). The potency of SFQSeM against oxidative stress as well as its oral bioavailability and low risk highlight its potential utility as an effective Se nutritional supplement.

Production and antioxidant capacity of bioactive peptides from plant biomass to counteract lipid oxidation

Preventing lipid oxidation, especially with the polyunsaturated fat-based products, is a major concern in sectors as agri-food and cosmetic. Even though the efficiency of synthetic antioxidants has been recognized, both consumers and manufacturers are looking for more innovative, healthy and quality products while rejecting synthetic additives due to their concern about safety, along with their environmental impact issues. In this context, plant biomass, which have shown to be rich in compounds, have raised interest for the isolation of novel naturally occurring antioxidants. Among their myriad of molecules, bioactive peptides, which are biologically active sequence of amino acid residues of proteins, seem to be of a great interest. Therefore, the number of identified amino acids sequences of bioactive peptides from plant biomass with potential antioxidant action is progressively increasing. Thus, this review provides a description of 129 works that have been made to produce bioactive peptides (hydrolysate, fraction and/or isolate peptide) from 55 plant biomass, along with the procedure to examine their antioxidant capacity (until 2019 included). The protein name, the process, and the method to concentrate or isolate antioxidant bioactive peptides, along with their identification and/or specificity were described. Considering the complex, dynamic and multifactorial physico-chemical mechanisms of the lipid oxidation, an appropriate in-vitro methodology should be better performed to efficiently probe the antioxidant potential of bioactive peptides. Therefore, the results were discussed, and perspective for antioxidant applications of bioactive peptides from plant biomass was argued.

TL15 of Arthrospira platensis sulfite reductase scavenges free radicals demonstrated in oxidant induced larval zebrafish (Danio rerio) model

The antioxidant role of sulfite reductase (SiR) derived from Arthrospira platensis (Ap) was identified through a short peptide, TL15. The study showed that the expression of ApSiR was highly expressed on day ten due to sulfur deprived stress in Ap culture. TL15 peptide exhibited strong antioxidant activity when evaluated using antioxidant assays in a concentration ranging from 7.8 and 125 μM. Further, the cytotoxicity of TL15 peptide was investigated, even at the higher concentration (250 μM), TL15 did not exhibit any toxicity, when tested in vitro using human leucocytes. Moreover, a potential reduction in reactive oxygen species (ROS) production was observed due to the treatment of TL15 peptide (>15.6 μM) to H2O2 exposed leucocytes. For the in vivo assessment of TL15 toxicity and antioxidant ability, experiments were performed in zebrafish (Danio rerio) larvae to analyse the developmental toxicity of TL15 peptide. Results showed that, exposure to TL15 peptide in tested concentrations ranging from 10, 20, 40, and 80 μM, did not affect the development and physiological parameters of the zebrafish embryo/larvae such as morphology, survival, hatching and heart rate. Fluorescent assay was performed using DCFH-DA (2,7-dichlorodihydrofluorescein diacetate) to examine the production of intracellular reactive oxygen species (ROS) in zebrafish treated with TL15 peptide during the embryo-larval stages. Fluorescent images showed that pre-treatment with TL15 peptide to attenuate the H2O2 induced ROS levels in the zebrafish larvae in a dose-dependent manner. Further to uncover the underlying biochemical and antioxidant mechanism, the enzyme activity of superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation (LPO) levels were studied in zebrafish larvae. TL15 pre-treated groups showed enhanced antioxidant enzyme activity, while the hydrogen peroxide (H2O2) exposed larvae showed significantly diminished activity. Overall results from the study revealed that, TL15 act as a potential antioxidant molecule with dose-specific antioxidant property. Thus, TL15 peptide could be an effective and promising source for biopharmaceutical applications.

AGLPM and QMDDQ peptides exert a synergistic action on memory improvement against scopolamine-induced amnesiac mice

This study aimed to explore the synergistic action of pentapeptides Gln-Met-Asp-Asp-Gln (QMDDQ) and Ala-Gly-Leu-Pro-Met (AGLPM) on memory improvement against scopolamine-induced impairment in mice compared to those of either peptide alone. In behavioral tests, the codelivery of QMDDQ and AGLPM was superior to the individual supplements of either peptide alone not only in enhancing the memory ability at training trials but also in recovering the memory impairment in scopolamine-induced amnesiac mice in test trials. Furthermore, combination treatment with QMDDQ and AGLPM could significantly reduce the acetylcholinesterase (AChE) level and increase the acetylcholine (ACh) level in the hippocampus, and noticeably improve the pathological morphology of the neuron cells in hippocampal regions CA1 and CA2 and dentate gyrus (DG). The findings indicated that the combination treatment with QMDDQ and AGLPM could improve the memory function by regulating the cholinergic system.

Immunomodulatory and Antioxidant Properties of Wheat Gluten Protein Hydrolysates in Human Peripheral Blood Mononuclear Cells

Peptides from several plant food proteins not only maintain the nutritional values of the original protein and decrease the environmental impact of animal agriculture, but also exert biological activities with significant health-beneficial effects. Wheat is the most important food grain source in the world. However, negative attention on wheat-based products has arose due to the role of gluten in celiac disease. A controlled enzymatic hydrolysis could reduce the antigenicity of wheat gluten protein hydrolysates (WGPHs). Therefore, the aims of the present study were to evaluate the effects of the in vitro administration of Alcalase-generated WGPHs on the immunological and antioxidant responses of human peripheral blood mononuclear cells (PBMCs) from 39 healthy subjects. WGPH treatment reduced cell proliferation and the production of the Type 1 T helper (Th1) and Th17 pro-inflammatory cytokines IFN-γ and IL-17, respectively. WPGHs also improved the cellular anti-inflammatory microenvironment, increasing Th2/Th1 and Th2/Th17 balances. Additionally, WGPHs improved global antioxidant capacity, increased levels of the reduced form of glutathione and reduced nitric oxide production. These findings, not previously reported, highlight the beneficial capacity of these vegetable protein hydrolysates, which might represent an effective alternative in functional food generation.

Antioxidant molecular mechanism of adenosyl homocysteinase from cyanobacteria and its wound healing process in fibroblast cells

An antioxidant molecule namely, adenosyl homocysteinase (AHc) was identified from the earlier constructed transcriptome database of Spirulina, where it was cultured in a sulphur deprived condition. From the AHc protein, a small peptide NL13 was identified using bioinformatics tools and was predicted to have antioxidant property. Further, the peptide was synthesised and its antioxidant mechanism was addressed at molecular level. NL13 was subjected to various antioxidant assays including DPPH assay, HARS assay, SARS Assay, NO assay and ABTS assay, where NL13 exhibited significant (P < 0.05) potential antioxidant activity compared to its antioxidant control, Trolox. Cytotoxicity was performed on Human whole blood and the cell viability was performed on VERO fibroblast cells. In both assays, it was found that NL13 did not exhibit any cytotoxic effect towards the cells. Further, the intracellular ROS was performed on Multimode reader followed by imaging on fluorescence microscope which showed scavenging activity even at lower concentration of NL13 (31.2 µM). An effective wound healing property of NL13 on VERO cells was confirmed by analysing the cell migration rate at two different time intervals (24 and 48 h). Overall, the study shows that NL13 peptide scavenges the intracellular oxidative stress.