Purification and identification of novel antioxidant peptides from watermelon seed protein hydrolysates and their cytoprotective effects on H2O2-induced oxidative stress

Study on the interventional effect and molecular mechanism of HSP72 in regulating oxidative stress by watermelon seed peptide RDPEER

Molecular docking and dynamics simulation techniques were used to analyze the binding capacity and stability of watermelon seed oligopeptides with heat shock protein 72 (HSP72), as well as the signaling pathway and mechanisms through cellular experiments. Computational simulation results indicated these peptides could form stable complexes with HSP72 through hydrogen bonds and other interactions, with the lowest free energy binding to RDPEER (-60.83 kcal/mol). In addition, by reducing HSP72 expression, RDPEER enhanced the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), and superoxide dismutase (SOD). Moreover, RDPEER decreased the levels of Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor kappa B subunit p65 (NF-κBp65), tumor necrosis factor-alpha (TNF-α), lipid peroxides (MDA), and reactive oxygen species (ROS), increasing cell survival rate by 20 % compared to control. Therefore, this study demonstrates that watermelon seed peptides regulate the Nrf2/NF-κB signaling axis by targeting HSP72, thereby maintaining cellular homeostasis.

Recent progress in chemistry and bioactivity of novel enzyme inhibitors from natural products: A comprehensive review

The essence of enzymes is to maintain the normal activities of living organisms by catalyzing metabolic reactions and regulating cells. Inhibiting enzyme activity can slow the progression of certain diseases and cure them, making enzymes one of the major targets for disease treatment. The search and development of novel enzyme inhibitors are of great significance for the treatment of certain major diseases. One of the most prominent features of natural products is their complex and diverse structures, which often compliments the synthetic capabilities of medicinal chemistry. Considering the biosynthetic processes of natural molecules in organisms, they exhibit higher similarity and binding potential with biological structures, enabling them to serve as ligands for various enzymes and receptors. In this review, we summarized a total of 226 novel natural products with enzyme inhibitory activity published in 49 articles over the past three years (2022-2024). These natural products (including terpenes, alkaloids, flavonoids, phenylpropanoids, polyketides, peptides, anthraquinones, etc.) are derived from plants, microorganisms, and marine organisms. We also discuss some synthetic analogs, with a focus on their structures and biological activities. This review provides useful information for the research and development of novel enzyme inhibitors.

Isolation and Identification of a Novel Antioxidant Peptide from Fermented Sea Cucumber (Stichopus japonicus) Intestine and Its Protective Effects on HepG2 Cells from Oxidative Damage

The development of antioxidant peptides that can benefit both human health and the environment is a major focus in antioxidant research. The study aimed to isolate and identify antioxidant peptides from fermented sea cucumber intestines and evaluate their cytoprotective effects against H2O2-induced oxidative damage in HepG2 cells. A new peptide AAAFEGKW (AP3) was obtained through liquid chromatography-tandem mass spectrometry and virtual molecular docking screening. Synthetic peptide AP3 (1000 μmol/L) demonstrated significant antioxidant activity, with 1,1-diphenyl-2-picrylhydrazyl, superoxide anion, and hydroxyl radical scavenging capacities of 52.99 ± 1.05, 65.10 ± 0.70, and 54.17 ± 0.85%, respectively. Cytoprotective analysis revealed that the peptide AP3 protected oxidatively damaged HepG2 cells by activating the Keap1/Nrf2 pathway, enhancing the activities of endogenous antioxidant enzymes, and reducing the levels of reactive oxygen species and malondialdehyde. Thus, AP3 exhibits strong potential as a novel antioxidant, making it suitable for applications in functional foods and food preservation.

Binding mechanism of metal ions (Ca2+, Cu2+ and Mg2+) with tetrapeptide FFDR: A combined experimental and quantum chemistry approach

A previous study demonstrated that a tetrapeptide FFDR derived from coix seed possesses antioxidant properties. In continuation of the study, Density Functional Theory (DFT) was employed to investigate the molecular-level complexation behaviour of FFDR with Ca2+, Cu2+, and Mg2+. DFT predictions were validated using spectroscopy and cellular model. The electronic properties revealed that Mg-FFDR, with its lower energy gap (1.733 eV), exhibits higher reactivity compared to Ca-FFDR which displayed higher stability (8.180 eV). The Quantum Theory of Atoms in Molecules (QTAIM) showed positive Laplacian values for all metal‑oxygen bonds, indicating the presence of coordination bonds characteristic of closed-shell interactions. Results from 1H NMR spectra revealed J-coupling patterns consistent with metal coordination for Mg and Ca-peptide complexes. FTIR spectra displayed distinct changes in the vibrational frequencies of functional groups involved in metal binding for all complexes. Both Mg-FFDR and Ca-FFDR demonstrated significant ROS scavenging activities, and enhanced SOD and CAT activities in HepG2 cells. These findings serve as a baseline for the rational design of metal-peptide complexes as functional foods or nutraceuticals.

Effect of cooking treatment on protein digestibility, peptide profile and potential bioactive peptides of beef tripe during in vitro gastrointestinal digestion

The purpose of this study was to understand the effects of cooking treatment on the protein hydrolysis of beef tripe and the release of potentially bioactive peptides using an in vitro gastrointestinal model. The results showed that digestion promoted the hydrolysis of proteins and release of free amino acids in beef tripe, but cooking treatment significantly reduced them. The sample of the cooked beef tripe after gastrointestinal digestion had the highest antioxidant activity. Peptidomic and in silico analyses of gastrointestinal digesta were performed to identify bioactive antioxidant peptide sequences. A total of 14 peptides were identified, which were confirmed with structural characteristics to exhibit antioxidation effects as well as a range of other biological functions, such as angiotensin I-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) inhibitory activities. These findings indicate that beef tripe and its digestive products have health-promoting potential, which can be utilized in functional food as ingredients.

A Comprehensive Review of the Nutritional and Health-Promoting Properties of Edible Parts of Selected Cucurbitaceae Plants

The Cucurbitaceae family includes commonly consumed plants such as pumpkin, watermelon, melon, horned melon, and cucumber, which are valued for their rich nutritional composition and health-promoting properties. These plants provide essential macronutrients, minerals, and bioactive compounds that contribute to their dietary and therapeutic significance. Particularly, Cucurbitaceae plants exhibit antidiabetic, hypolipidemic, antioxidant, and anticancer properties, making them valuable in addressing metabolic disorders and alleviating health risks associated with oxidative stress. This review aims to systematize current knowledge on selected cucurbits' nutritional composition, mineral content, and phytochemical profile. It also examines their caloric value, glycemic index, and glycemic load, offering insight into their potential role in dietary strategies for patients with obesity, insulin resistance, or diabetes. Additionally, this review explores often-overlooked by-products, including seeds, leaves, and flowers, which are rich in bioactive compounds with potential health benefits. By compiling and analyzing existing data, this review highlights the nutritional and functional potential of Cucurbitaceae plants, reinforcing their significance in a health-promoting diet and disease prevention.

Effects of whey protein-inulin conjugates with varying degrees of glycosylation on hepatic antioxidant capacity, immunomodulation and gut microbiota in mice

In this study, whey protein isolate-inulin (WPI-In) conjugates with varying degrees of glycosylation (DG) were prepared, characterized, and examined for their potential immunomodulatory effects and regulation of gut microbiota in mice. The data indicated that an increase in DG significantly affects the microstructure and functionalities of WPI-In conjugates. The WPI-In conjugates with high DG promoted the growth and development of the thymus while altering gut microbiota composition by increasing the relative abundance of Bacteroidetes and reducing that of Firmicutes. Additionally, the WPI-In conjugates enhanced liver antioxidant capacity and the secretion of immunoglobulin G, and elevated levels of anti-inflammatory cytokines (IL-4 and IL-2), while decreasing pro-inflammatory cytokine (TNF-α) content in serum. Spearman correlation analysis suggested that the enhancement of liver antioxidant capacity and regulation of immune-related indicators may be associated with the gut microbiota altered by WPI-In conjugates. Therefore, WPI-In conjugates demonstrate beneficial properties, indicating potential applications in food systems.

Novel anti-oxidative peptides from equine hemoplasma protein hydrolysates: Purification, identification and protective effects on Caco-2 cells

In this study, we purified and identified antioxidant peptides from equine plasma protein hydrolysates and assessed their protective effects against H2O2-induced oxidative stress in Caco-2 cells. Four antioxidant peptides were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in equine plasma protein hydrolysate, namely: GTMVGC (567.69 Da), FGMTST (662.88 Da), VGYHSHF (847.01 Da) and ALSPFFKE (939.18 Da). Among them, ALSPFFKE showed the strongest antidigestive properties after modelled digestion studies. Moreover, ALSPFFKE enhanced intracellular superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities while significantly reducing reactive oxygen species accumulation and malondialdehyde formation in Caco-2 cells. The molecular docking analysis suggested that ALSPFFKE achieves regulation of the Keap1-Nrf2 pathway mainly by forming multiple hydrogen bonds and hydrophobic interactions with key amino acids (Arg380, Ser555, Gln530, Tyr334) in Keap1. These findings suggested that equine plasma peptides hold significant promise for the development of novel, potent, and stable antioxidant functional foods.

Enrichment of antioxidant peptide from rice protein hydrolysates via rice husk derived biochar

In this study, rice husk biochar was engineered with abundant iron ion sites to enhance the enrichment of antioxidant peptides from rice protein hydrolysates through metal-chelating interactions. The π-π interactions and metal ion chelation were identified as the primary mechanisms for the enrichment process. Through peptide sequencing, four peptides were identified: LKFL (P1: Leu-Lys-Phe-Leu), QLLF (P2: Gln-Leu-Leu-Phe), WLAYG (P3: Trp-Leu-Ala-Tyr-Gly), and HFCGG (P4: His-Phe-Cys-Gly-Gly). The vitro analysis and molecular docking revealed that peptides P1-P4 possessed remarkable scavenging ability against radicals and Fe2+ chelating ability. Notably, peptide P4 showed radical scavenging activity comparable to glutathione (GSH) against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-3-ethylbenzthiazoline-6-sulphonate (ABTS) radicals. Cellular experiments further confirmed that peptide P4 effectively protected HepG2 cells from oxidative stress-induced damage. The modified rice husk biochar proved to be an effective means for enriching rice antioxidant peptides from protein hydrolysates.

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.

In vitro evaluation of multifunctional peptides PW, PF, PPG, PM, IW, and SW for metabolic syndrome management

Multifunctional peptides derived from various food sources, including ancestral grains, hold significant promise for managing metabolic syndrome. These bioactive peptides exhibit diverse properties that collectively contribute to improving the components of metabolic syndrome. In this study, we investigated the in vitro multifunctionality of six peptides (PW, PM, SW, PPG, PW, and IW) identified through in silico analysis and chemically synthesized. These peptides were evaluated for their potential to address metabolic syndrome-related activities such as antidiabetic, antiobesity, antihypertensive, and antioxidative properties. Assessment included their capacity to inhibit key enzymes associated with these activities, as well as their free radical scavenging and cellular antioxidative activities. Principal component analysis was employed to cluster the peptides according to their multifunctionality. Our results revealed that peptides containing tryptophan (SW, PW, and IW) exhibited the most promising multifunctional attributes, with SW showing particularly high potential. This multifunctional peptide represents a promising avenue for addressing metabolic syndrome.

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.

Isolation, identification, and chelation mechanism of ferrous-chelating peptide from peanut protein hydrolysate

BACKGROUND

Peanut peptides can chelate iron but their chelation mechanism remains unclear. The purpose of this study is to separate peanut ferrous-chelating peptides and explore the chelation mechanism of peanut peptides with iron.

RESULTS

Peanut peptide component F-122, which had a higher chelation rate, was separated using ultrafiltration, gel filtration chromatography, and ion exchange chromatography, achieving a ferrous chelation rate of 90.7%. Six peptide segments were screened and their amino acid sequences were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Spectral analysis confirmed that the chelation between peanut peptides and ferrous ions occurred and a new substance was formed. Molecular docking simulation indicated that the amino acids in peanut peptides involved in the chelating reaction were glutamic acid, arginine, glycine, threonine, phenylalanine, and lysine. The binding sites included the main chain oxygen atom, side chain oxygen atom, and carboxyl oxygen atom of amino acid.

CONCLUSION

The isolated peanut peptide had a higher ferrous-chelation rate. The chelating mechanism of peanut peptide with ferrous ion was elucidated. This study provides a theoretical basis for the development of new peptide-ferrous preparations. © 2024 Society of Chemical Industry.

Regulation of redox enzymes by nutraceuticals: a review of the roles of antioxidant polyphenols and peptides

Redox enzymes are essential components of the cellular defence system against oxidative stress, which is a common factor in various diseases. Therefore, understanding the role of bioactive nutraceuticals in modulating the activity of these enzymes holds immense therapeutic potential. This paper provides a comprehensive review of the regulation of redox enzymes in cell and animal models by food-derived bioactive nutraceuticals, focusing on polyphenols and peptides. Specifically, this paper discusses the regulation of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), NAPDH oxidase, xanthine oxidase (XO), myeloperoxidase (MPO), and haem oxygenase (HO) in cell and animal models. Polyphenols, which are abundant in fruits, vegetables, and beverages, have diverse antioxidant properties, including direct scavenging of reactive oxygen species and regulation of transcription factors such as nuclear factor erythroid 2-related factor 2, which leads to the increased expression of the redoxenzymes SOD, HO, and GPx. Similarly, bioactive peptides from various food proteins can enhance antioxidative enzyme activity by regulating gene expression and directly activating the enzyme CAT. In other cases, an antioxidative response requires the downregulation or inhibition of the redox enzymes XO, MPO, and NAPDH oxidase. This paper highlights the potential of bioactive nutraceuticals in mitigating oxidative stress-related diseases and their mechanisms in modulating the redox enzyme expression or activity. Furthermore, the review highlights the need for further research to uncover new therapeutic strategies using nutraceuticals for enhancing cellular antioxidant defence mechanisms and improving health outcomes.

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

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

Novel Antioxidant Peptides from Fermented Whey Protein by Lactobacillus rhamnosus B2-1: Separation and Identification by in Vitro and in Silico Approaches

Whey is a byproduct of the dairy industry and is rich in protein. To enhance the significance of such byproducts and find efficacious antioxidants for combating oxidative stress, this study reported on the preparation, purification, and identification of novel peptides with antioxidant activities from whey protein metabolites following fermentation by Lactobacillus rhamnosus B2-1. The isolation and identification processes involved macroporous adsorption resin column chromatography, gel filtration column chromatography, and liquid chromatography-tandem mass spectrometry. Therein, three novel antioxidant peptides (PKYPVEPF, LEASPEVI, and YPFPGPIHNS) were selected to be synthesized, and they demonstrated remarkable antioxidant activities in vitro chemical assays. PKYPVEPF, LEASPEVI, and YPFPGPIHNS (100 μg/mL) displayed a notable cytoprotective impact on HepG2 cells under oxidative stress induced by H2O2, increasing the cell viability from 49.02 ± 3.05% to 88.59 ± 10.49%, 82.38 ± 19.16%, and 85.15 ± 7.19%, respectively. Moreover, the peptides boosted the activities of catalase and superoxide dismutase in damaged cells and reduced reactive oxygen species levels. The molecular docking studies highlighted that these antioxidant peptides efficiently bound to key amino acids in the Kelch domain of Keap1, thereby preventing the interaction between Keap1 and Nrf2. In conclusion, PKYPVEPF, LEASPEVI, and YPFPGPIHNS demonstrated substantial antioxidant activity, suggesting their potential for widespread application as functional food additives and ingredients.

Identification and molecular docking of novel antioxidant peptides from Candida utilis

The current trend is the promotion of antioxidants that are beneficial for both health and the environment. Candida utilis have garnered considerable attention due to their commendable attributes such as non-toxicity and the ability to thrive in waste. Therefore, Candida utilis was used as raw material to isolate and identify new antioxidant peptides by employing methods such as ultrafiltration, DEAE Sepharose Fast Flow, and liquid chromatography-tandem mass spectrometry. The antioxidant mechanism of peptides was investigated by molecular docking. The properties of antioxidant peptides were evaluated using a variety of computational tools. This study resulted in the identification of two novel antioxidant peptides. According to the molecular docking results, the antioxidant mechanism of Candida utilis peptides operates by obstructing the entry to the myeloperoxidase activity cavity. The (-) CDOCKER energy of antioxidant peptides was 6.2 and 6.1 kcal/mol, respectively. Additionally, computer predictions indicated that antioxidant peptides exhibited non-toxicity and poor solubility.

Antioxidant Function and Application of Plant-Derived Peptides

With the development of society and the improvement of people's health consciousness, the demand for antioxidants is increasing. As a natural antioxidant with no toxic side effects, antioxidant peptides are widely used in food, cosmetics, medicine, and other fields because of their strong antioxidant capacity and easy absorption by the human body. Plant-derived antioxidant peptides have attracted more attention than animal-derived antioxidant peptides because plants are more diverse than animals and produce a large number of protein-rich by-products during the processing of their products, which are the main source of antioxidant peptides. In this review, we summarize the source, structure and activity, other biological functions, mechanism of action, and comprehensive applications of plant antioxidant peptides, and look forward to their future development trends, which will provide a reference for further research and development of plant antioxidant peptides.

Purification, identification and molecular docking studies of antioxidant and anti-inflammatory peptides from Edible Bird's Nest

This study investigated antioxidant and anti-inflammatory peptides from Edible Bird's Nest (EBN). The prepared EBN peptides were sequentially separated, purified, and successively identified by ultrafiltration, gel filtration and mass spectrometry techniques. Four potential antioxidant and anti-inflammatory peptides were identified as Peptide 1 (LFWSPSVYLK), Peptide 2 (GWPHLEDNYLDW), Peptide 3 (NPPADLHK) and Peptide 4 (GDLAYLDQGHR). Molecular docking analysis revealed that Peptide 1 and Peptide 2 can competitively interrupt the formation of Keap1-Nrf2 due to the presence of hydrophobic and antioxidant amino acids in their peptide sequences. Peptide 3 and Peptide 4 have a strong effect on interacting with the binding site of IKK-β due to the interaction of anti-inflammatory amino acids and C-terminal arginine/lysine. The four peptides were synthesised and validated for their antioxidant and anti-inflammatory activities. The results suggest that the four peptides may serve as promising bioactive peptides for preventing oxidative stress and inflammation-related diseases.

Walnut protein isolate-epigallocatechin gallate nanoparticles: A functional carrier enhanced stability and antioxidant activity of lycopene

Walnut isolate protein (WPI)-epigallocatechin gallate (EGCG) conjugates can be employed to creat food-grade delivery systems for preserving bioactive compounds. In this study, WPI-EGCG nanoparticles (WENPs) were developed for encapsulating lycopene (LYC) using the ultrasound-assisted method. The results indicated successful loading of LYC into these WENPs, forming the WENPs/LYC (cylinder with 200-300 nm in length and 14.81-30.05 nm in diameter). Encapsulating LYC in WENPs led to a notable decrease in release rate and improved stability in terms of thermal, ultraviolet (UV), and storage conditions compared to free LYC. Simultaneously, WENPs/LYC exhibited a synergistic and significantly higher antioxidant activity with an EC50 value of 23.98 μg/mL in HepG2 cells compared to free LYC's 31.54 μg/mL. Treatment with WENPs/LYC led to a dose-dependent restoration of intracellular antioxidant enzyme activities (SOD, CAT, and GSH-Px) and inhibition of intracellular malondialdehyde (MDA) formation. Furthermore, transcriptome analysis indicated that enrichment in glutathione metabolism and peroxisome processes following WENPs/LYC addition. Quantitative real-time reverse transcription PCR (qRT-PCR) verified the expression levels of related genes involved in the antioxidant resistance pathway of WENPs/LYC on AAPH-induced oxidative stress. This study offers novel perspectives into the antioxidant resistance pathway of WENPs/LYC, holding significant potential in food industry.

Nanozyme-Catalyzed Colorimetric Detection of the Total Antioxidant Capacity in Body Fluids by Paper-Based Microfluidic Chips

Total antioxidants play a crucial role in human health, and detection of the total antioxidant capacity (TAC) has broad application prospects in fields such as food safety, environmental assessment, and disease diagnosis. However, a long detection time, cumbersome steps, high cost, reliance on professional equipment, and nonportability still remain significant challenges. In this work, an efficient strategy of point-of-care testing (POCT) of the TAC in body fluids by nanozyme-catalyzed colorimetric paper-based microfluidic sensors is proposed. The paper-based microfluidic sensors coupled with a smartphone can reduce testing costs and provide portability. The nanozyme prepared by the solvothermal method presents Michaelis constants of 0.11 and 0.129 mM for H2O2 and TMB, respectively. A method for immobilizing nanozymes and chromogenic agents on a paper-based microfluidic chip is established. Based on smartphone photography and image grayscale extraction, the TAC can be qualitatively detected with a detection limit and linear range of 33.4 and 50-700 μM, respectively. Furthermore, the proposed sensor can realize the one-step quantitative analysis of the TAC in body fluids (blood, saliva, and sweat) within 15 min. The proposed nanozyme-catalyzed colorimetric paper-based microfluidic sensors presented in this study exhibit promising application prospects in the fields of biochemical analysis and POCT.

Preparation of antioxidant peptides from yak skin gelatin and their protective effect on myocardial ischemia reperfusion injury

We herein report a study on the antioxidant peptides that show potential in alleviating myocardial ischemia reperfusion injury (MI/RI). Yak skin gelatin fraction Ac (YSG-Ac), obtained through ultrafiltration and gel filtration with Sephadex G-15, exhibits a favorable nutrient composition, high foaming capacity and stability, and resistance against gastrointestinal digestion. LC-MS/MS analysis reveals that YSG-Ac contains 26 peptide segments with sequence lengths of 8 to 12 amino acids. Online screening suggests that the antioxidant capacity of YSG-Ac is mainly attributed to the presence of hydrophobic and antioxidant amino acids. In vitro, our results demonstrate the MI/RI protective effects of YSG-Ac by effectively repairing H2O2-induced oxidative damage in H9c2 cells, which is achieved by inhibiting malondialdehyde (MDA) levels, and increasing glutathione peroxidase (GSH-pX) and superoxide dismutase (SOD) activity. In vivo, our results further confirm the effectiveness of YSG-Ac in narrowing the area of myocardial infarction, decreasing MDA levels, increasing SOD activity, and reducing the content of lactate dehydrogenase (LDH) in a mouse MI/RI model. Molecular docking analysis indicates that PGADGQPGAK with xanthine dehydrogenase (XDH) and GAAGPTGPIGS with tumor necrosis factor-alpha (TNF-α) exhibit strong bonding capability, and other related targets also show certain binding ability toward YSG-Ac. This suggests that YSG-Ac can regulate MI/RI through multiple targets and pathways. Overall, our findings highlight the potential of YSG-Ac as a functional food ingredient with antioxidant and MI/RI protective characteristics.

Preparation, identification and molecular docking of two novel anti-aging peptides from perilla seed

Perilla seed meal is an important agricultural by-product of perilla oil extraction. The antioxidant and anti-aging activities of perilla seed meal protein hydrolysate were investigated, and the bioactive peptides were identified to maximize the utilization of perilla seed meal resources. Anti-aging peptides were identified using a combination of peptidomics and in silico bioinformatics. Furthermore, the potential molecular mechanism of these peptides was explored through molecular docking and RT-PCR. The results showed a significant anti-aging properties of F2 (MW 3 kDa ∼5 kDa) by inhibition of reactive oxygen species (ROS) production and β-galactosidase activity. Nine novel peptides were identified from F2 and subsequently synthesized to explore their bioactivities. The two peptides, NFF and PMR, were found to promote the proliferation of keratinocytes (HaCaT cells) and suppress the level of ROS and the activity of β-galactosidase. Both peptides exhibited a strong binding affinity with the Keap1 protein. Additionally, NFF and PMR downregulated the expression of matrix metalloproteinases (MMPs) and the degradation of collagens (COLs). The potential molecular mechanism underlying the anti-aging properties of perilla seed meal peptides might involve the competitive binding of Keap1 to facilitate the release of Nrf2 and activation of NF-κB signal pathway. This study provides a theoretical basis for the application of perilla seed meal peptides in functional cosmetics and presents a novel perspective for the investigation of additional food-derived peptides.

Citrullus mucosospermus Extract Reduces Weight Gain in Mice Fed a High-Fat Diet

This study aimed to investigate the therapeutic potential of Citrullus mucosospermus extract (CME) in counteracting adipogenesis and its associated metabolic disturbances in murine models. In vitro experiments utilizing 3T3-L1 preadipocytes revealed that CME potently inhibited adipocyte differentiation, as evidenced by a dose-dependent reduction in lipid droplet formation. Remarkably, CME also attenuated glucose uptake and intracellular triglyceride accumulation in fully differentiated adipocytes, suggesting its ability to modulate metabolic pathways in mature adipose cells. Translating these findings to an in vivo setting, we evaluated the effects of CME in C57BL/6N mice fed a high-fat diet (HFD) for 10 weeks. CME administration, concomitantly with the HFD, resulted in a significant attenuation of body weight gain compared to the HFD control group. Furthermore, CME treatment led to substantial reductions in liver weight, total fat mass, and deposits of visceral and retroperitoneal adipose tissue, underscoring its targeted impact on adipose expansion. Histological analyses revealed the remarkable effects of CME on hepatic steatosis. While the HFD group exhibited severe lipid accumulation within liver lobules, CME dose-dependently mitigated this pathology, with the highest dose virtually abolishing hepatic fat deposition. An examination of adipose tissue revealed a progressive reduction in adipocyte hypertrophy upon CME treatment, culminating in a near-normalization of adipocyte morphology at the highest dose. Notably, CME exhibited potent anti-inflammatory properties, significantly attenuating the upregulation of pro-inflammatory cytokines' mRNA levels (TNF-α, IL-1β and IL-6) in the livers of HFD-fed mice. This suggests a potential mechanism through which CME may exert protective effects against inflammation associated with obesity and fatty liver disease.

Citrullus mucosospermus Extract Exerts Protective Effects against Methionine- and Choline-Deficient Diet-Induced Nonalcoholic Steatohepatitis in Mice

In recent years, there has been increasing interest in exploring the potential therapeutic advantages of Citrullus mucosospermus extracts (CME) for nonalcoholic steatohepatitis (NASH). In this study, we investigated the therapeutic effects of CME on NASH using a mice model. High-performance liquid chromatography (HPLC) was employed to identify cucurbitacin E and cucurbitacin E-2-O-glucoside from the CME. Although CME did not significantly alter the serum lipid levels in methionine- and choline-deficient (MCD) mice, it demonstrated a protective effect against MCD diet-induced liver damage. CME reduced histological markers, reduced alanine transaminase (ALT) and aspartame transaminase (AST) levels, and modulated key NASH-related genes, including C/EBPα, PPARγ, Fas, and aP2. In addition, CME was found to restore hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) activity, both crucial for fat catabolism, and reduced the levels of pro-inflammatory cytokines. Furthermore, CME demonstrated the potential to mitigate oxidative stress by maintaining or enhancing the activation and expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and superoxide dismutase (SOD), both pivotal players in antioxidant defense mechanisms. These findings underscore the promising therapeutic potential of CME in ameliorating liver damage, inflammation, and oxidative stress associated with NASH.

Comprehensive Review on Fruit Seeds: Nutritional, Phytochemical, Nanotechnology, Toxicity, Food Biochemistry, and Biotechnology Perspective

Fruit seeds are leftovers from a variety of culinary sectors. They are generally unutilized and contribute greatly to global disposals. These seeds not only possess various nutritional attributes but also have many heath-beneficial properties. One way to make use of these seeds is to extract their bioactive components and create fortified food items. Nowadays, researchers are highly interested in creating innovative functional meals and food components from these unconventional resources. The main objective of this manuscript was to determine the usefulness of seed powder from 70 highly consumed fruits, including Apple, Apricot, Avocado, Banana, Blackberry, Blackcurrant, Blueberry, Cherry, Common plum, Cranberry, Gooseberry, Jackfruit, Jamun, Kiwi, Lemon, Mahua, Mango, Melon, Olive, Orange, and many more have been presented. The nutritional attributes, phytochemical composition, health advantages, nanotechnology applications, and toxicity of these fruit seeds have been fully depicted. This study also goes into in-depth detailing on creating useful food items out of these seeds, such as bakery goods, milk products, cereal-based goods, and meat products. It also identifies enzymes purified from these seeds along with their biochemical applications and any research openings in this area.

A novel neuroprotective peptide YVYAETY identified and screened from Flammulina velutipes protein hydrolysates attenuates scopolamine-induced cognitive impairment in mice

Flammulina velutipes protein hydrolysates are known for their abundant amino acids and excellent developmental values. This study aimed to identify and screen neuroprotective peptides from F. velutipes protein hydrolysates in vitro and validate the protective effects of YVYAETY on memory impairment in scopolamine-induced mice. The F. velutipes protein was hydrolyzed by simulated gastrointestinal digestion, followed by purification through ultrafiltration and gel chromatography. The fraction exhibiting the strongest neuroprotective activity was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The main identified peptides (SDLKPADF, WNDHYY, YVYAETY, and WFHPLF) effectively mitigated excessive ROS production by increasing SOD and GSH-px activities while inhibiting cell apoptosis and mitochondrial membrane potential (MMP) collapse against oxidative stress in Aβ25-35-induced HT22 cells. By molecular docking, the interaction between peptides and the active site of the Keap1-Kelch domain reveals their capacity to regulate the Keap1/Nrf2/HO-1 pathway. In vitro, the peptide YVYAETY had the best effect and can be further validated in vivo. The behavioral tests showed that YVYAETY improved scopolamine-induced cognitive impairment in mice. YVYAETY also alleviated neuron damage including neuron vacuolation and pyknotic nuclei in the hippocampus. Furthermore, it significantly inhibited oxidative stress and suppressed the activation of the Nrf2 pathway. Therefore, this study revealed that YVYAETY had the potential to serve as a novel neuroprotective agent.

Novel Peptides from Sturgeon Ovarian Protein Hydrolysates Prevent Oxidative Stress-Induced Dysfunction in Osteoblast Cells: Purification, Identification, and Characterization

This study aimed to explore antioxidant peptides derived from sturgeon (Acipenser schrenckii) ovaries that exhibit antiosteoporotic effects in oxidative-induced MC3T3-E1 cells. The F3-15 component obtained from sturgeon ovarian protein hydrolysates (SOPHs) via gel filtration and RP-HPLC significantly increased the cell survival rate (from 49.38 ± 2.88 to 76.26 ± 2.09%). Two putative antioxidant-acting peptides, FDWDRL (FL6) and FEGPPFKF (FF8), were screened from the F3-15 faction via liquid chromatography-tandem mass spectrometry (LC-MS/MS) and through prediction by computer simulations. Molecular docking results indicated that the possible antioxidant mechanisms of FL6 and FF8 involved blocking the active site of human myeloperoxidase (hMPO). The in vitro tests showed that FL6 and FF8 were equally adept at reducing intracellular ROS levels, increasing the activity of antioxidant enzymes, and protecting cells from oxidative injuries by inhibiting the mitogen-activated protein kinase (MAPK) pathway and activating the phosphoinositide-3 kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase-3β (GSK-3β) signaling pathway. Moreover, both peptides could increase differentiation and mineralization abilities in oxidatively damaged MC3T3-E1 cells. Furthermore, FF8 exhibited high resistance to pepsin and trypsin, showcasing potential for practical applications.

Novel antioxidant peptides from sheep plasma protein hydrolysates: Purification, identification and cytoprotective effects against H2O2-induced oxidative stress

This study sought to purify and identify antioxidant peptides from sheep (Ovis aries) plasma protein hydrolysates and assess their protective impacts on H2O2-induced Caco-2 cells. The purification process involved reversed high-performance liquid chromatography, anion-exchange chromatography, and Sephadex G-25. Three peptides, namely Trp-Glu-Glu-Pro-Ala-Met (WEEPAM), Ser-Leu-His-Phe-Met-Glu (SLHFME), and His-Cys-Thr-Thr-Phe-Met-Ile, with molecular weights of 761.84, 762.87, and 852.03 Da, respectively, were identified by liquid chromatography with tandem mass spectrometry. Among the three antioxidant peptides, superoxide radical (O2 -) radical scavenging capacity of WEEPAM and SLHFME was not significantly different from glutathione (GSH) (p > 0.05), while their 1,1-diphenyl-2-picrylhydrazyl radical scavenging capacity was greater than GSH (p < 0.05). WEEPAM revealed increased antioxidant activity after pepsin and trypsin hydrolysis under an in vitro digestion model. In addition, WEEPAM inhibited oxidative damage in Caco-2 cells by significantly reducing reactive oxygen species accumulation, early apoptosis, malondialdehyde formation, and increasing intracellular superoxide dismutase, glutathione peroxidase, and catalase activities.

Identification and anti-oxidative potential of milk fat globule membrane (MFGM)-derived bioactive peptides released through in vitro gastrointestinal digestion

This study investigated the stability of milk fat globule membrane (MFGM) protein under simulated gastrointestinal conditions using an in vitro enzymatic digestion method. The optimal hydrolysis conditions were determined by monitoring the changes in particle size and zeta-potential of MFGM protein hydrolysates over time. Furthermore, the distribution of small molecular weight peptides with antioxidant activity was explored through DEAE-52 combined with in vitro cell experiments. Two novel antioxidant peptides (TGIIT and IITQ) were identified based on molecular docking technology and evaluated their potential scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS+) radicals. TGIIT and IITQ also demonstrated remarkable abilities in promoting mitochondrial biogenesis and activating Keap1/Nrf2 signaling pathway, which can effectively counteract skeletal muscle dysfunction induced by oxidative stress. Thus, MFGM-derived antioxidant peptides have the potential to be employed in food to regulate muscle protein metabolism and alleviate sarcopenia.

Alcalase-hydrolyzed insoluble soybean meal hydrolysate aggregates: Structure, bioactivity, function properties, and influences on the stability of oil-in-water emulsions

We studied the influences of hydrolysis time on the structure, functional properties, and emulsion stability of insoluble soybean meal hydrolysate aggregates (ISMHAs). We assume that the ISMHAs produced by soybean meal can be used as emulsifiers to prepare stable emulsions. The molecular weights of these ISMHAs were below 53 kDa. After hydrolysis, a decrease in α-helices and an increase in random coils indicated that the soybean meal proteins were unfolding. Moreover, the fluorescence intensity, UV absorption, and surface hydrophobicity of ISMHAs increased. These results would contribute to their antioxidant activity and functional properties. Additionally, the 90-min ISMHA sample exhibited the highest ABTS+• scavenging activity (80.02 ± 4.55 %), foaming stability (52.92 ± 8.06 %), and emulsifying properties (emulsifying activity index of 97.09 m2/g; emulsifying stability index of 371.47 min). The 90-min ISMHA emulsion exhibited the smallest particle size and excellent storage stability. Soybean meal peptide by-product emulsifier has potential for sustainable application.

Comparison of characteristics and antioxidant activities of sesame protein hydrolysates and their fractions

Sesame meal is a by-product obtained from oil extraction. We investigated the characteristics and antioxidant activities of a sesame protein hydrolysate (SPH-B), as well as its peptide fractions. Four peptide fractions (F1; >100 kDa, F2; 10-100 kDa, F3; 1-10 kDa, and F4; <1 kDa) of SPH-B were prepared. The characteristics and antioxidant properties of SPH-B and its peptide fractions were evaluated. Sesame protein (SP) contained protein fractions with molecular weights ranging from 10 to 44 kDa, whereas SPH-B had peptide fractions ranging from 8 to 44 kDa. The peptide fractions had molecular weight ranging from 7 to 10 kDa. The four peptide fractions had a higher α-helix content and lower surface hydrophobicity than SPH-B and SP. They exhibited better antioxidant properties, with higher ABTS and DPPH radical scavenging activities, higher metal chelating activity, and greater inhibition of linoleic acid peroxidation, suggesting that sesame peptide fractions can use as plant-based functional ingredients and potentially health-promoting properties.

Identification and Functional Validation of Two Novel Antioxidant Peptides in Saffron

Saffron (Crocus sativus L.) is one of the most expensive spices in the world, boasting rich medicinal and edible value. However, the effective development of active natural substances in saffron is still limited. Currently, there is a lack of comprehensive studies on the saffron stigma protein, and the main effect peptides have not been identified. In this study, the total protein composition of saffron stigmas was analyzed, and two main antioxidant peptides (DGGSDYLGK and VDPYFNK) were identified, which showed high antioxidant activity. Then, the stability of two peptides was further evaluated. Furthermore, our results suggested that these two peptides may protect HepG2 cells from H2O2-induced oxidative damage by significantly improving the activity of endogenous antioxidant enzymes and reducing the malondialdehyde (MDA) content. Collectively, we identified two peptides screened from the saffron protein possessing good antioxidant activity and stability, making them promising candidates for use as functional foods, etc., for health promotion. Our findings indicated that proteomic analysis together with peptide identification is a good method for exploitation and utilization of spice plants.

Purification and Identification of Peptides from Hydrilla verticillata (Linn. f.) Royle with Cytoprotective and Antioxidative Effect against H2O2-Treated HepG2 Cells

Antioxidant peptides were purified from Hydrilla verticillata (Linn. f.) Royle (HVR) protein hydrolysate by ultrafiltration, gel filtration chromatography, and semipreparative reversed-phase HPLC and identified by UPLC-ESI-MS/MS. Therein, TCLGPK and TCLGER were selected to be synthesized, and they displayed desirable radical-scavenging activity to ABTS (99.20 ± 0.56-99.20 ± 0.43%), DPPH (97.32 ± 0.59-97.56 ± 0.97%), hydroxyl radical (54.32 ± 1.27-70.42 ± 2.01%), and superoxide anion (42.93 ± 1.46-52.62 ± 1.11%) at a concentration of 0.96 μmol/mL. They possessed a cytoprotective effect against H2O2-induced oxidative stress in HepG2 cells in a dose-dependent manner. 1.6 μmol/mL of the two peptides could perfectly protect HepG2 cells from H2O2-induced injury. The TCLGPK exhibited higher antioxidant activity and cytoprotective effect than TCLGER. Western blot and molecular docking results indicated that the two peptides achieved antioxidant ability and cytoprotective effect by combining with Kelch-like ECH-associated protein 1 (Keap1) to activate the Keap1-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elements signaling pathway, leading to the activity and expression of the related antioxidases in the pathway significantly up-regulating and the intracellular reactive oxygen species level, lipid peroxidation, and cell apoptosis rate significantly down-regulating.

Size-dependent toxicity of polystyrene microplastics on the gastrointestinal tract: Oxidative stress related-DNA damage and potential carcinogenicity

Microplastics (MPs) and nanoplastics (NPs) have been generally regarded as emerging pollutants and received worldwide attention in recent years. Water and food consumption are the primary pathways for human exposure to MPs/NPs, thus gastrointestinal tracts may be susceptible to their toxicity. Although the recent report has indicated the presence of MPs/NPs in multiple human organs, little is known about their gastric effects. Therefore, this study focused on the adverse effects of polystyrene microplastics (PS-MPs) on gastric epithelium in vivo and in vitro. Surface-enhanced Raman spectroscopy (SERS) revealed the distribution of PS-MPs was associated with their particle sizes, and predominantly concentrated in gastric tissues. Gastric barrier injury and mitochondrial damage were observed in rats after exposure to PS-MPs. Compared with the larger ones, polystyrene nanoplastics (PS-NPs) more significantly reduced the activity of antioxidant enzymes while enhancing the level of MDA, 8-OhdG and γ-H2AX. Meanwhile, PS-MPs caused upregulation of β-catenin/YAP through redox-dependent regulation of nucleoredoxin (NXN) and dishevelled (Dvl). These findings supported the size-dependent effects of PS-MPs on oxidative stress and DNA damage. Moreover, the redox-dependent activation of the β-catenin/YAP cascade suggested a novel toxic mechanism for PS-MPs and implied the potential carcinogenic effects.

Identification and evaluation of antioxidant peptides from highland barley distiller's grains protein hydrolysate assisted by molecular docking

The aim of this study was to identify antioxidant peptides from highland barley distiller's grains and evaluate their antioxidant activity in vitro. The results showed that the enzymatic hydrolysate of highland barley distiller's grains prepared by ultrasonic assisted alkaline protease had antioxidant properties, aromatic amino acids accounted for 61.48% of the total free amino acids and acidic/basic amino acids accounted for 40.82% of the total hydrolyzed amino acids in enzymatic hydrolysate. Ultrafiltration component F1 (Mw < 1 kDa) had the highest DPPH, ABTS and hydroxyl radical scavenging activity and ferrous ion chelating activity, which were 93.92%, 69.59%, 50.27% and 0.71, respectively. Four peptides were identified and screened by LC-MS/MS and the P1 (SWDNFFR) and P4 (WDWVGGR) showed high scavenging ability of DPPH free radical (70.23%-62.84%) and ABTS free radical (30.87%-60.54%). Molecular docking showed that P1 and P4 formed multiple hydrogen bonds with central residues of MPO.

Identification of novel antioxidant collagen peptides for preventing and treating H2 O2 -induced oxidative stress in HepG2 cells through in vitro and in silico approaches

BACKGROUND

Nowadays, the prevalence of oxidative stress-related chronic diseases is increasing. The identification of novel antioxidant collagen peptides to counteract oxidative stress for individuals' health has gained significant attention.

RESULTS

In this study, collagen peptides with antioxidant activities were separated and identified by ion chromatography, reversed-phase high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry. The identified antioxidant collagen peptides were further screened by molecular docking for Keap1-targeted peptide inhibitors and their theoretical interaction mechanisms were investigated. Four novel antioxidant collagen peptides, GPAGPIGPVG, GPAGPpGPIG, ISGPpGPpGPA and IDGRPGPIGPA, with high binding affinity to Keap1 were selected. Molecular docking results demonstrated that the putative antioxidant mechanism of the four antioxidant collagen peptides contributed to their blockage of Keap1-Nrf2 interactions. The results of antioxidant activity of the four antioxidant collagen peptides proved that IDGRPGPIGPA exerted a high scavenging capacity for DPPH and ABTS free radicals, while GPAGPpGPIG improved the resistance of cells to hydrogen peroxide-induced oxidative damage by promoting the activation of intracellular antioxidant enzymes and the production of reduced glutathione in human hepatoma (HepG2) cells.

CONCLUSION

The antioxidant collagen peptides (GPAGPIGPVG, GPAGPpGPIG, ISGPpGPpGPA and IDGRPGPIGPA) will be developed as novel functional food for human health in the near future. © 2023 Society of Chemical Industry.

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.

Animal-derived free hydrolysate in animal cell culture: Current research and application advances

Fetal bovine serum (FBS) plays a crucial role in the composition of animal cell culture medium. However, conventional serum-based medium face numerous challenges. The use of animal-derived free hydrolysate (ADFH) has garnered significant attention in research and applications as a viable alternative to FBS-containing medium in animal cell culture. This article provides a comprehensive overview of the effects, mechanisms of action, and applications of ADFH in animal cell culture. ADFH serves as an effective substitute for FBS-containing medium, enhancing various cellular processes, including cell proliferation, viability, protein synthesis, production, survival, and stability. Several mechanisms of action for ADFH have been elucidated through scientific investigations, such as nutrient provision, activation of signaling pathways, regulation of protein synthesis and folding, protection against oxidative damage and apoptosis, as well as cell cycle regulation. Researches and applications of ADFH represent a promising approach to overcoming the limitations of FBS-containing medium and advancing the field of animal cell culture. This review provides a theoretical foundation for promoting the development of sustainable and alternative hydrolysates, as well as the continued progress of animal cell culture.

Preparation, Characterization, and Antioxidant Properties of Selenium-Enriched Tea Peptides

The research on the activity of selenium (Se)-enriched agricultural products is receiving increasing attention since Se was recognized for its antioxidant activities and for its enhancement of immunity in trace elements. In this study, antioxidant Se-containing peptides, namely, Se-TAPepI-1 and Se-TAPepI-2, were optimally separated and prepared from Se-enriched tea protein hydrolysates by ultrafiltration and Sephadex G-25 purification, and subsequently, their physicochemical properties, oligopeptide sequence, and potential antioxidant mechanism were analyzed. Through the optimization of enzymatic hydrolysis conditions, the Se-enriched tea protein hydrolyzed by papain exhibited a better free radical scavenging activity. After separation and purification of hydrolysates, the two peptide fractions obtained showed significant differences in selenium content, amino acid composition, apparent morphology, peptide sequence, and free radical scavenging activity. Therein, two peptides from Se-TAPepI-1 included LPMFG (563.27 Da) and YPQSFIR (909.47 Da), and three peptides from Se-TAPepI-2 included GVNVPYK (775.42 Da), KGGPGG (552.24 Da), and GDEPPIVK (853.45 Da). Se-TAPepI-1 and Se-TAPepI-2 could ameliorate the cell peroxidation damage and inflammation by regulating NRF2/ARE pathway expression. Comparably, Se-TAPepI-1 showed a better regulatory effect than Se-TAPepI-2 due to their higher Se content, typical amino acid composition and sequence, higher surface roughness, and a looser arrangement in their apparent morphology. These results expanded the functional activities of tea peptide and provided the theoretical basis for the development of Se-containing peptides from Se-enriched tea as a potential natural source of antioxidant dietary supplements.

Bioactive peptides PDBSN improve mitochondrial function and suppression the oxidative stress in human adiposity cells

Introduction: Mitochondria are essential for generating cellular energy and are significant in the pathogenesis of obesity. Peptide PDBSN has been demonstrated to inhibit the adipogenic differentiation of adipocytes in vitro and improves metabolic homoeostasis in vivo. Therefore, in this study, we further investigated the effects of PDBSN on the morphology, synthesis, and function of adipocyte mitochondria. Methods: Human visceral and subcutaneous primary preadipocytes (HPA-v and HPA-s) were cultured into mature adipocytes. Intracellular triglyceride content was assessed using oil-red O staining and tissue triglyceride determination. Gene and protein levels associated with mitochondrial synthesis were detected using real-time quantitative polymerase chain reaction and western blotting. Mitochondrial membrane potentials and ROS were detected using fluorescent indicators. Morphological changes were observed by electron microscopy. Results: PDBSN significantly increased mitochondrial membrane potential (MMP), while decreasing intracellular triglyceride (TG) and intracellular reactive oxygen species (ROS) levels. On the other hand, the transcription and protein levels of genetic marker genes PGC1-α and MTFA were significantly up-regulated after PDBSN administration. Further studies showed that transcriptional and protein levels of mitochondrial fusion and fission genetic markers MFN1, MFN2, NRF1, and DRP1 increased. Conclusion: PDBSN significantly reduces intracellular TG and ROS levels and increases MMP. The maximum respiratory capacity in adults significantly increases after PDBSN administration, and ROS levels are significantly reduced. This suggests that PDBSN improves mitochondrial function to some extent, which not only provides an essential basis for the pathophysiology of obesity but also provides insights for the development of new drugs to treat obesity and metabolic diseases.

Synthesis and biological evaluation of capsaicin analogues as antioxidant and neuroprotective agents

Capsaicin and its analogues 3a-3q were designed and synthesized as potential new antioxidant and neuroprotective agents. Many analogues exhibited good antioxidant effects, and some showed more potent free radical scavenging activities than the positive drug quercetin (IC50 = 8.70 ± 1.75 μM for DPPH assay and 13.85 ± 2.87 μM for ABTS assay, respectively). The phenolic hydroxyl of capsaicin analogues was critical in determining antioxidant activity. Among these compounds, 3k displayed the most potent antioxidant activity. Cell vitality tests revealed that the representative compound 3k was good at protecting cells from H2O2-induced oxidative damage at low concentrations (cell viability increased to 90.0 ± 5.5% at 10 μM). In addition, the study demonstrated that 3k could reduce intracellular ROS accumulation and increase GSH levels to prevent H2O2-induced oxidative stress in SY5Y cells. In the mitochondrial membrane potential assay, 3k significantly increased the MMP level of SY5Y cells treated with H2O2 and played an anti-neuronal cell death role. These results provide a promising strategy to develop novel capsaicin analogues as potential antioxidant and neuroprotective agents.

Identification, in silico selection, and mechanism study of novel antioxidant peptides derived from the rice bran protein hydrolysates

The work aimed to assess the antioxidant ability and obtain a new antioxidant peptide from rice bran protein. Rice bran protein was hydrolyzed by Alcalase, Neutral, Pepsin, Chymotrypsin, and Trypsin, separately. Trypsin hydrolysate (T-RBPH) showed high Fe²⁺ chelating activity (IC₅₀, 2.271 ± 0.007 mg/mL), DPPH and hydroxyl radical scavenging ability (IC₅₀, 0.191 ± 0.006 and 1.038 ± 0.034 mg/mL). Moreover, T-RBPH could alleviate the H₂O₂-induced oxidative damage in Caco-2. The T-RBPH was purified and identified by UF, GF, FPLC, and LC-MS/MS. Finally, 9-amino acid peptide-AFDEGPWPK with low molecular weight (1045.48 Da), high antioxidant activity, good safety, and solubility was screened by in silico method and chemical oxidation determination, and its interaction with Keap1 was also demonstrated. The ORAC and DPPH radical scavenging ability of AFDEGPWPK were 44.16 ± 0.79 and 28.38 ± 0.14 μmol TE/mM. Moreover, the Molecular docking and Western blot (WB) results showed that AFDEGPWPK could enter the binding pocket in the Kelch domain and activate Keap1/Nrf2/HO-1 pathway.

Preparation and identification of novel antioxidant peptides from camel bone protein

Collagen hydrolysates are a vital source of bioactive peptides. The objective of this study was to prepare camel bone collagen hydrolysates with antioxidant activity, and to identify the peptides responsible for the antioxidant activity. To this end, single-factor and orthogonal tests were performed to explore the optimum preparation conditions. A hydrolysis time of 5 h, enzyme:substrate ratio of 1200 U/g, pH of 7.0, and a material:water ratio of 1:3.0 were adopted. Subsequently, the hydrolysates were purified using a series of chromatography procedures, and three novel peptides, GPPGPPGPPGPPGPPSGGFDF (hydroxylation), PATGDLTDFLK, and GSPGPQGPPGSIGPQ, possessing antioxidant abilities, were identified from the fraction using liquid chromatography-tandem mass spectrometry. The peptide PATGDLTDFLK showed excellent DPPH scavenging activity (39%) and a good cytoprotective effect on H₂O₂-induced oxidative stress damage in HepG2 cells with a 21.1% increase observed.

Investigation of the optimal production conditions for egg white hydrolysates and physicochemical characteristics

This study aimed to investigate the potential of egg white protein hydrolysate (EWH) as a functional food by identifying the optimum production conditions for EWH with response surface methodology (the results of the sensory evaluation were considered as an essential quality indicator). At the same time, its physicochemical and biological activity was also evaluated. The optimal economic production conditions were selected: substrate concentration of 12.5%, enzyme content of 7.5%, and hydrolysis time at 100 min. The degree of hydrolysis (DH %) was 13.51%. In addition, to the better acceptance of the evaluation, it also helps to reduce the production cost of the protein hydrolysate, which is beneficial to future processing and applications. The antioxidant capacity experiments showed that EWH has good antioxidant activity, which presents a dose-dependent relationship. Hence, this study provides a theoretical basis for future research and application of EWH for processing applications, including dietary supplementation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05708-0.

Purification and Identification of Novel Antioxidant Peptides from Hydrolysates of Peanuts (Arachis hypogaea) and Their Neuroprotective Activities

Peanut (Arachis hypogaea) peptides have various functional activities and a high utilization value. This study aims to isolate and characterize antioxidant peptides from peanut protein hydrolysates and further evaluate their neuroprotection against oxidative damage to PC12 cells induced by 6-hydroxydopamine (6-OHDA). After the peanut protein was hydrolyzed with pepsin and purified using ultrafiltration and gel chromatography, six peptides were identified and sequenced by high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Out of these six peptides, Pro-Gly-Cys-Pro-Ser-Thr (PGCPST) exhibited a desirable antioxidant capacity, as determined using the 1,1-diphenyl-2-picrylhydrazyl, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, and hydroxyl radical scavenging assays. Moreover, our results indicated that the peptide PGCPST effectively increased the cell viability and reduced the cell apoptosis in 6-OHDA-induced PC12. RNA sequencing further showed that the neuroprotective effect of the peptide PGCPST was mediated via sphingolipid metabolism-related pathways. With further research efforts, the peptide PGCPST was expected to develop into a new neuroprotective agent.

Molecular Docking Revealed the Potential Anti-Oxidative Stress Mechanism of the Walnut Polypeptide on HT22 Cells

The preparation of novel antioxidant peptides from food raw materials is one of the research focuses, but there are fewer studies on the preparation of antioxidant peptides from walnut meal, a by-product of processing walnuts. This study analyzed the antioxidant properties and protective effects of walnut protein hydrolyzed by alkaline protease and trypsin on the oxidative stress of HT22 cells. The peptides were identified by UPLC-MS/MS, and the anti-oxidative peptides were screened based on virtual computer tools. The potential anti-oxidative stress mechanism of the walnut polypeptide on HT22 cells was explored by molecular docking. The results revealed that walnut protein hydrolysates (WPH) with molecular weights of less than 1 kDa had good antioxidant properties and inhibited oxidative damage of HT22 cells by regulating the levels of reactive oxygen species (ROS) and antioxidant enzyme catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Six of the ninety identified new peptides showed good solubility, non-toxicity, and bioactivity. The molecular docking results showed that the six peptides could dock with Keap1 successfully, and EYWNR and FQLPR (single-letter forms of peptide writing) could interact with the binding site of Nrf2 in the Keap1-Kelch structural domain through hydrogen bonds with strong binding forces. The results of this study provided important information on the antioxidant molecular mechanism of the walnut polypeptide and provided a basis for further development of walnut antioxidant polypeptide products.