Preparation and identification of antioxidant peptides from cottonseed proteins

Preparation, bioactivities, and food industry applications of tuber and tuberous roots peptides: A review

Tuber and tuberous roots proteins are important sources for producing bioactive peptides. The objective of this review is to present the current research status of tubers and tuberous roots bioactive peptides (TTRBP), including its preparation methods, purification techniques, structure identification approaches, biological functions, and applications in the food industry. Moreover, the current challenges and future development trends of TTRBP are elucidated. Currently, TTRBP are mainly produced by enzymatic hydrolysis and fermentation. Pretreatment like high static pressure, ultrasound and microwave can assist enzymatic hydrolysis and facilitate TTRBP production. In addition, TTRBP are structurally diverse, which is related to the molecular weight, amino acids composition, and linkage mode. Accordingly, they have various biological activities (such as antioxidant, antihypertensive, hypoglycemic) and have been utilized in the food industry as functional ingredients and food additives. This review will provide valuable insights for the optimal utilization of tuber and tuberous roots.

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.

Recent progress in the preparation of bioactive peptides using simulated gastrointestinal digestion processes

Bioactive peptides (BAPs) represent a unique class of peptides known for their extensive physiological functions and their role in enhancing human health. In recent decades, owing to their notable biological attributes such as antioxidant, antihypertensive, antidiabetic, and anti-inflammatory activities, BAPs have received considerable attention. Simulated gastrointestinal digestion (SGD) is a technique designed to mimic physiological conditions by adjusting factors such as digestive enzymes and their concentrations, pH levels, digestion duration, and salt content. Initially established for analyzing the gastrointestinal processing of foods or their constituents, SGD has recently become a preferred method for generating BAPs. The BAPs produced via SGD often exhibit superior biological activity and stability compared with those of BAPs prepared via other methods. This review offers a comprehensive examination of the recent advancements in BAP production from foods via SGD, addressing the challenges of the method and outlining prospective directions for further investigation.

Development of QSARs for cysteine-containing di- and tripeptides with antioxidant activity:influence of the cysteine position

Antioxidants agents play an essential role in the food industry for improving the oxidative stability of food products. In the last years, the search for new natural antioxidants has increased due to the potential high toxicity of chemical additives. Therefore, the synthesis and evaluation of the antioxidant activity in peptides is a field of current research. In this study, we performed a Quantitative Structure Activity Relationship analysis (QSAR) of cysteine-containing 19 dipeptides and 19 tripeptides. The main objective is to bring information on the relationship between the structure of peptides and their antioxidant activity. For this purpose, 1D and 2D molecular descriptors were calculated using the PaDEL software, which provides information about the structure, shape, size, charge, polarity, solubility and other aspects of the compounds. Different QSAR model for di- and tripeptides were developed. The statistic parameters for di-peptides model (R2train = 0.947 and R2test = 0.804) and for tripeptide models (R2train = 0.923 and R2test = 0.847) indicate that the generated models have high predictive capacity. Then, the influence of the cysteine position was analyzed predicting the antioxidant activity for new di- and tripeptides, and comparing them with glutathione. In dipeptides, excepting SC, TC and VC, the activity increases when cysteine is at the N-terminal position. For tripeptides, we observed a notable increase in activity when cysteine is placed in the N-terminal position.

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.

Cottonseed meal protein hydrolysate influences growth performance, carcass characteristics, serum biochemical indices, and intestinal morphology in yellow-feather broilers

This study investigated the effects of cottonseed meal protein hydrolysate (CPH) on the growth performance, carcass characteristics, serum biochemical indices, intestinal morphology, and enzyme activities of yellow-feather broilers. We randomly divided 240 chicks into four groups, each with six replicates: a basal diet with 0% (CON), 1% (LCPH), 3% (MCPH), or 5% (HCPH) CPH. The trail spanned 63 days and included three phases: Days 1-21, 22-42, and 43-63. Increased average daily gain (ADG) and decreased ratio of feed to gain (F/G) with LCPH were observed in 21-day-old broilers (P < 0.05). MCPH led to higher ADG and average daily feed intake (ADFI) in 42-day-old broilers (P < 0.05). Additionally, CPH supplementation resulted in increased dressing percentage, percentage of half-eviscerated yield, percentage of eviscerated yield, breast muscle rate, and leg muscle rate were observed (P < 0.05) with diet. The serum levels of total protein (TP), high-density lipoprotein cholesterol (HDL-C), calcium (Ca), and phosphorus (P) were enhanced, and blood urea nitrogen (BUN) and triglyceride (TG) levels decreased with diet and CPH (P < 0.05). CPH increased the length of the jejunum and ileum and the weight of the duodenum, jejunum, and ileum in 21-day-old broilers (P < 0.05). Alterations in the duodenal villus structure in broilers occurred on Days 21 and 42, and the CPH groups performed better; however, a similar change occurred in the jejunum on Days 42 and 63 (P < 0.05). MCPH and HCPH enhanced trypsin activity in the duodenum of 21-day-old and 63-day-old broilers (p < 0.05). Chymotrypsin activity increased (P > 0.05) in the duodenum of 63-day-old broilers fed MCPH. Lipase activity increased (P < 0.05) in the jejuna of 21-day-old broilers treated with HCPH. CPH increased trypsin activity in the ilea of 21-day-old broilers (P < 0.05). These results showed that CPH influenced the growth performance, carcass characteristics, serum biochemical indices, and intestinal morphology of yellow-feather broilers, which are related to growth stage. The recommended CPH level in broilers is 1% before 21 days of age and 3% after 21 days of age.

HPLC purification of antioxidant and antibacterial peptides from a lichen "Parmotrema perlatum (Huds.) M. Choisy": Identification by LC-MS/MS peptide mass fingerprinting

Parmotrema perlatum, a lichen belonging to the family Parmeliaceae, is well known for its culinary benefits and aroma used as a condiment in Indian homes is also known as the "black stone flower" or "kalpasi" in India. This research intends to analyze the antioxidant power of the crude extracts using four pH-based buffers solubilized proteins/peptides and RP-HPLC fractions of P. perlatum obtained by purification. The proteins that were extracted from the four different buffers were examined using LC-MS/MS-based peptide mass fingerprinting. When compared to the other buffers, the 0.1 M of Tris-HCl buffer pH 8.0 solubilized proteins/peptides had the strongest antioxidant capacity. The sequential purification of the peptide was carried out by using a 3-kDa cut-off membrane filter and semipreparative RP-HPLC. Additionally, the purified fractions of the peptide's antioxidant activity were assessed, and effects were compared with those of the crude and 3 kDa cut--off membrane filtrates. The peptide fractions were sequenced by LC-MS/MS, which reveals that fraction 2 from RP-HPLC with the sequence LSWFMVVAP has shown the highest antioxidant potential in comparison with other fractions which can serve as the potential natural antioxidant drug. Further, fraction 2 also showed antibacterial activity against the selected microorganisms.

The antioxidant peptides from walnut protein hydrolysates and their protective activity against alcoholic injury

In this study, walnut protein was hydrolyzed, separated by ultrafiltration, purified by RP-HPLC, identified by LC-MS/MS, and screened by molecular docking to finally obtain three novel antioxidant peptides HGEPGQQQR (1189.584 Da), VAPFPEVFGK (1089.586 Da) and HNVADPQR (949.473 Da). These three peptides exhibited excellent cellular antioxidant activity (CAA) with EC50 values of 0.0120 mg mL-1, 0.0068 mg mL-1, and 0.0069 mg mL-1, respectively, which were superior to that of the positive control GSH (EC50: 0.0122 mg mL-1). In the ethanol injury model, three antioxidant peptides enhanced the survival of cells treated with ethanol from 47.36% to 62.69%, 57.06% and 71.64%, respectively. Molecular docking results showed that the three antioxidant peptides could effectively bind to Keap1, CYP2E1 and TLR4 proteins. These results suggested that walnut-derived antioxidant peptides could be potential antioxidants and hepatoprotective agents for application in functional foods.

Exploring of multi-functional umami peptides from Stropharia rugosoannulata: Saltiness-enhancing effect and mechanism, antioxidant activity and potential target sites

Umami peptides enhance flavor and offer potential health benefits. We analyzed the taste-value profiles of five novel umami peptides from Stropharia rugosoannulata using E-tongue, exhibiting significant saltiness characteristics. While the peptides PHEMQ and SEPSHF exhibited higher saltiness, their mixture with salt did not enhance saltiness compared to individual peptides. Surprisingly, SGCVNEL, which was initially weak in saltiness, showed remarkably enhanced saltiness when mixed with salt, possibly due to have strong binding with receptors. Molecular docking elucidated the salt-forming mechanism of TMC4, highlighting the P2-domain and hydrogen bonds' role in the composite structure stability. Evaluation of the antioxidant activity evaluation demonstrated dose-dependent effects primarily through free radical scavenging via the single-electron transfer potential mechanism for SGCVNEL, EPLCNQ, and ESCAPQL. Docking experiments with antioxidant targets revealed varied binding stabilities, indicating diverse antioxidant effects of the peptides. These findings provide valuable insights into the exploration and application of versatile bioactive flavor peptides.

Structure, physicochemical properties, and biological activities of protein hydrolysates from Zanthoxylum seed

BACKGROUND

Zanthoxylum seed, as a low-cost and easily accessible plant protein resource, has good potential in the food industry. But protein and its hydrolysates from Zanthoxylum seed are underutilized due to the dearth of studies on them. This study aimed to investigate the structure and physicochemical and biological activities of Zanthoxylum seed protein (ZSP) hydrolysates prepared using Protamex®, Alcalase®, Neutrase®, trypsin, or pepsin.

RESULTS

Hydrolysis using each of the five enzymes diminished average particle size and molecular weight of ZSP but increased random coil content. ZSP hydrolysate prepared using pepsin had the highest degree of hydrolysis (24.07%) and the smallest molecular weight (<13 kDa) and average particle size (129.80 nm) with the highest solubility (98.9%). In contrast, ZSP hydrolysate prepared using Alcalase had the highest surface hydrophobicity and foaming capacity (88.89%), as well as the lowest foam stability (45.00%). Moreover, ZSP hydrolysate prepared using Alcalase exhibited the best hydroxyl-radical scavenging (half maximal inhibitory concentration (IC50 ) 1.94 mg mL-1 ) and ferrous-ion chelating (IC50 0.61 mg mL-1 ) activities. Additionally, ZSP hydrolysate prepared using pepsin displayed the highest angiotensin-converting enzyme inhibition activity (IC50 0.54 mg mL-1 ).

CONCLUSION

These data showed that enzyme hydrolysis improved the physicochemical properties of ZSP, and enzymatic hydrolysates of ZSP exhibited significant biological activity. These results provided validation for application of ZSP enzymatic hydrolysates as antioxidants and antihypertensive agents in the food or medicinal industries. © 2023 Society of Chemical Industry.

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.

Effects of an Akt-activating peptide obtained from walnut protein degradation on the prevention of memory impairment in mice

Akt acts as a central protein influencing multiple pathologies in neurodegenerative diseases including AD and PD, and using Akt activators is a promising management strategy. The current study characterized the effects of an Akt-activating peptide (Glu-Pro-Glu-Val-Leu-Pro, EPEVLR) obtained from walnut protein degradation on D-gal-induced memory impairment in mice. EPEVLR was obtained by hydrolysis of walnut proteins, identification of peptide sequences, and screening for molecular docking sequentially. The MWM test in mice indicated that the oral administration of EPEVLR (80, 200 and 400 mg per kg per day) significantly (p < 0.05) reversed D-gal-induced memory impairment. WB tests of the mouse hippocampus confirmed that EPEVLR could activate Akt by promoting its phosphorylation. In addition, further characterization (including TEM, ELISA, and immunohistochemistry) related to Akt phosphorylation showed lower Aβ and p-tau levels, as well as more autophagosomes than those in the model group. Moreover, the EPEVLR treatment significantly increased Lactobacillus abundance and reduced Helicobacter abundance in the gut microbiome and caused up-regulation of SCFAs and down-regulation of LPS of serum metabolites. Therefore, EPEVLR ingestion reversed cognitive impairment symptoms, possibly related to the activation of Akt and regulation of the intestinal flora pathway. Consumption of an EPEVLR-containing diet is beneficial for treating cognitive dysfunction.

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.

New Insights into Antioxidant Peptides: An Overview of Efficient Screening, Evaluation Models, Molecular Mechanisms, and Applications

Antioxidant peptides are currently a hotspot in food science, pharmaceuticals, and cosmetics. In different fields, the screening, activity evaluation, mechanisms, and applications of antioxidant peptides are the pivotal areas of research. Among these topics, the efficient screening of antioxidant peptides stands at the forefront of cutting-edge research. To this end, efficient screening with novel technologies has significantly accelerated the research process, gradually replacing the traditional approach. After the novel antioxidant peptides are screened and identified, a time-consuming activity evaluation is another indispensable procedure, especially in in vivo models. Cellular and rodent models have been widely used for activity evaluation, whilst non-rodent models provide an efficient solution, even with the potential for high-throughput screening. Meanwhile, further research of molecular mechanisms can elucidate the essence underlying the activity, which is related to several signaling pathways, including Keap1-Nrf2/ARE, mitochondria-dependent apoptosis, TGF-β/SMAD, AMPK/SIRT1/PGC-1α, PI3K/Akt/mTOR, and NF-κB. Last but not least, antioxidant peptides have broad applications in food manufacture, therapy, and the cosmetics industry, which requires a systematic review. This review introduces novel technologies for the efficient screening of antioxidant peptides, categorized with a new vision. A wide range of activity evaluation assays, encompassing cellular models, as well as rodent and non-rodent models, are provided in a comprehensive manner. In addition, recent advances in molecular mechanisms are analyzed with specific cases. Finally, the applications of antioxidant peptides in food production, therapy, and cosmetics are systematically reviewed.

Target Functionalized Carbon Dot Nanozymes with Dual-Model Photoacoustic and Fluorescence Imaging for Visual Therapy in Atherosclerosis

Multifunctional nanomedicines have been used in atherosclerosis theranostics. Herein, phosphatidylserine-specific peptide CLIKKPF-functionalized carbon-dots nanozymes (pep-CDs) are reported for specific and efficient noninvasive theranostic of atherosclerosis. Surprisingly, pep-CDs are discovered to not only inherit the inherent properties of carbon dots (CDs), including deep-red fluorescence emission, photoacoustic response, and superoxide dismutase-like antioxidant, and anti-inflammatory activities but also possess the ability to target recognition on foam cells and target localization on plaques due to the specific interaction of CLIKKPF with phosphatidylserine on the membrane outer surface of foam cells. Furthermore, the target localization effect of pep-CDs vastly promotes the efficient accumulation of CDs in plaque, thus maximizing AS theranostic of CDs. Interestingly, pep-CDs could be developed to image plaque for monitoring atherosclerosis pathological progression in real-time resulting from the different content of foam cells. This work on the one hand proposes a simple and feasible strategy to construct theranostic nanoplatform employing only a single functional unit (i.e., multifunctional CDs) to simplify the fabrication procedure, on the other hand, highlights the advantages of the active target auxiliary mode for atherosclerosis theranostic applications.

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.

Physicochemical, functional, and antioxidant properties of black soldier fly larvae protein

This study explores the multifaceted attributes of black soldier fly larvae protein (BSFLP), focusing on its physicochemical, functional, and antioxidant properties. BSFLP is characterized by 16 amino acids, with a predominant random coil secondary structure revealed by circular dichroism spectra. Differential scanning calorimetry indicates a substantial thermal denaturation temperature of 97.63°C. The protein exhibits commendable solubility, emulsification, and foaming properties in alkaline and low-salt environments, albeit with reduced water-holding capacity and foam stability under elevated alkaline and high-temperature conditions. In vitro assessments demonstrate that BSFLP displays robust scavenging proficiency against 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), and hydroxyl radicals, with calculated EC50 values of 1.90 ± 0.57, 0.55 ± 0.01, and 1.14 ± 0.02 mg/mL, respectively, along with notable reducing capabilities. Results from in vivo antioxidant experiments reveal that BSFLP, administered at doses of 300 and 500 mg/kg, significantly enhances the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) (p < 0.05) while simultaneously reducing malondialdehyde levels in both serum and tissues of d-galactose-induced oxidative stress in mice. Moreover, the protein effectively attenuates oxidative damage in liver and hippocampal tissues. These findings underscore the potential utility of BSFLP as a natural antioxidant source, with applications spanning the food, pharmaceutical, and cosmetic industries. PRACTICAL APPLICATION: Black soldier fly larvae protein emerges as an environmentally sustainable reservoir of natural antioxidants, holding significant promise for the food, pharmaceutical, and cosmetic sectors. Its advantageous amino acid composition, robust thermal resilience, and impressive functional attributes position it as a compelling subject for continued investigation and advancement in various applications.

Peptides with biological and technofunctional properties produced by bromelain hydrolysis of proteins from different sources: A review

Bromelains are cysteine peptidases with endopeptidase action (a subfamily of papains), obtained from different parts of vegetable belonging to the Bromeliaceae family. They have some intrinsic medical activity, but this review is focused on their application (individually or mixed with other proteases) to produce bioactive peptides. When compared to other proteases, perhaps due to the fact that they are commercialized as an extract containing several proteases, the hydrolysates produced by this enzyme tends to have higher bioactivities than other common proteases. The peptides and the intensity of their final properties depend on the substrate protein and reaction conditions, being the degree of hydrolysis a determining parameter (but not always positive or negative). The produced peptides may have diverse activities such as antioxidant, antitumoral, antihypertensive or antimicrobial ones, among others or they may be utilized to improve the organoleptic properties of foods and feeds. Evolution of the use of this enzyme in this application is proposed to be based on a more intense direct application of Bromeliaceae extract, without the cost associated to enzyme purification, and the use of immobilized biocatalysts of the enzyme by simplifying the enzyme recovery and reuse, and also making the sequential hydrolysis using diverse proteases possible.

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.

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.

Discovery of ACE Inhibitory Peptides Derived from Green Coffee Using In Silico and In Vitro Methods

Inhibition of angiotensin-I converting enzyme (ACE) is an important means of treating hypertension since it plays an important regulatory function in the renin-angiotensin system. The aim of this study was to investigate the ACE inhibitory effect of bioactive peptides from green coffee beans using in silico and in vitro methods. Alcalase and thermolysin were employed to hydrolyze protein extract from coffee beans. Bioactive peptides were identified by LC-MS/MS analysis coupled with database searching. The potential bioactivities of peptides were predicted by in silico screening, among which five novel peptides may have ACE inhibitory activity. In vitro assay was carried out to determine the ACE inhibitory degree. Two peptides (IIPNEVY, ITPPVMLPP) were obtained with IC50 values of 57.54 and 40.37 μM, respectively. Furthermore, it was found that two inhibitors bound to the receptor protein on similar sites near the S1 active pocket of ACE to form stable enzyme-peptide complexes through molecular docking, and the Lineweaver-Burk plot showed that IIPNEVY was a noncompetitive inhibitor, and ITPPVMLPP was suggested to be a mixed-type inhibitor. Our study demonstrated that two peptides isolated from coffee have potential applications as antihypertensive agents.

Improvement of amphipathic properties with molecular structure unfolding and activation of cottonseed protein as ultra stable and safe emulsifier by deamidation

By-product cottonseed proteins are excellent options for numerous applications due to their superior properties and lower cost. However, its complex folded structure and large molecular weight lead to lower reactivity and insufficient amphiphilicity. Cottonseed protein isolate (CPI) is less-soluble in water. Therefore, we improved the amphiphilicity of CPI with associated hydrolysis, molecular structure unfolding, and activation by alkaline-induced deamidation (at 24, 36, and 72 h) and produced three cottonseed protein hydrolysates CPH 24, 36, and 72. FTIR/UV-CD measurements confirmed the conformational changes and conversion of the structural content. Particle size decreased 2503.4-771.8 nm, while surface hydrophobicity (133.5-326.7), carboxyl content (1.13 × 10־3-2.09 × 10־3), and flexibility increased, signifying hydrolysis, unfolding, and amphiphilicity improvement. Longer deamidation (CPH 72) exhibited the best properties, its prepared emulsions were long-term stable under all the environmental stresses without visible phase separation after at least 40 days of storage except at pH 4. Compared to CPI, it had smaller droplets (939.3-264.9 nm) and larger absolute ζ-potential (-26.5 to -58.0 mV). From the in-vitro cytotoxicity test, deamidated CPI is extremely safer than commonly used synthetic surfactants. This research provides a new method for producing multifunctional emulsifiers from CPI, which could be utilized in the development of functional foods/non-foods.

Novel and efficient techniques in the discovery of antioxidant peptides

As a research hotspot in food science and nutrition, antioxidant peptides can function by scavenging free radicals, inhibiting peroxides, and chelating metal ions. Therefore, how to efficiently discover and screen antioxidant peptides has become a key issue in research and production. Traditional discovery methods are time-consuming and costly, but also challenging to resolve the quantitative structure-activity relationship of antioxidant peptides. Several novel techniques, including artificial intelligence, molecular docking, bioinformatics, quantum chemistry, phage display, switchSENSE, surface plasmon resonance, and fluorescence polarization, are emerging rapidly as solutions. These techniques possess efficient capability for the discovery of antioxidant peptides, even with the potential for high-throughput screening. In addition, the quantitative structure-activity relationship can be resolved. Notably, combining these novel techniques can overcome the drawbacks of a single one, thus improving efficiency and expanding the discovery horizon. This review has summarized eight novel and efficient techniques for discovering antioxidant peptides and the combination of techniques. This review aims to provide scientific evidence and perspectives for antioxidant peptide research.

Bioactive peptides derived from Radix Angelicae sinensis inhibit ferroptosis in HT22 cells through direct Keap1-Nrf2 PPI inhibition

The development of natural peptides as direct Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid2-related factor 2 (Nrf2) protein-protein interaction (PPI) inhibitors for antioxidant and anti-ferroptotic purposes has attracted increasing interest from chemists. Radix Angelicae sinensis (RAS) is a widely used traditional Chinese medicine with antioxidant capability. However, few studies have screened Keap1-Nrf2 PPI inhibitory RAS peptides (RASPs). This study optimized the extraction and hydrolysis protocols of RAS protein using response surface methodology coupled with Box-Behnken design. The molecular weight distribution of the prepared hydrolysates was analysed to obtain active fractions. Subsequently, ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry was employed to identify RASPs. Various in vitro and in silico assays were conducted to evaluate the antioxidant and anti-ferroptotic effects of RASPs. The results revealed that at least 50 RASPs could be obtained through the optimized protocols. RASPs containing active residues effectively scavenged 2,2-diphenyl-1-picrylhydrazyl radical and 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid radical cation. They also showed cytoprotective effect against erastin-induced ferroptosis in HT22 cells, which was characterized by the activation of Nrf2 and weakened under the incubation of an Nrf2 inhibitor. Moreover, RASPs could bind to Keap1 and then dissociate Nrf2 in molecular dynamics simulations. In conclusion, RASPs exhibit antioxidant activity through hydrogen atom transfer and electron transfer mechanisms. Importantly, they also inhibit ferroptosis by directly inhibiting Keap1-Nrf2 PPI.

Streamlined Efficient Synthesis and Antioxidant Activity of γ-[Glutamyl](n≥1)-tryptophan Peptides by Glutaminase from Bacillus amyloliquefaciens

As a group of naturally occurring peptides in various foods, γ-glutamyl peptides possess a unique Kokumi taste and health benefits. However, few studies have focused on the functionality of γ-glutamyl peptides. In this study, the γ-[glutamyl] _{(n=1, 2, 3)}-tryptophan peptides were synthesized from a solution of glutamine (Gln) and tryptophan (Trp) employing L-glutaminase from Bacillus amyloliquefaciens. Four different γ-glutamyl peptides were identified from the reaction mixture by UPLC-Q-TOF-MS/MS. Under optimal conditions of pH 10, 37 °C, 3 h, 0.1 mol/L Gln: 0.1 mol/L Trp = 1:3, and glutaminase at 0.1% (m/v), the yields of γ-l-glutamyl-l-tryptophan (γ-EW), γ-l-glutamyl-γ-l-glutamyl-l-tryptophan (γ-EEW) and γ-l-glutamyl-γ-l-glutamyl-γ-l-glutamyl-l-tryptophan (γ-EEEW) were 51.02%, 26.12% and 1.91% respectively. The antioxidant properties of the reaction mixture and the two peptides (γ-EW, γ-EEW) identified from the reaction media were further compared. Results showed that γ-EW exhibited the highest DPPH^•, ABTS^•+ and O₂^•--scavenging activity (EC₅₀ = 0.2999 mg/mL, 67.6597 μg/mL and 5.99 mg/mL, respectively) and reducing power (EC₅₀ = 4.61 mg/mL), while γ-EEW demonstrated the highest iron-chelating activity (76.22%). Thus, the synthesized mixture may be used as a potential source of antioxidant peptides for food and nutraceutical applications.

Marine-Derived Bioactive Peptides Self-Assembled Multifunctional Materials: Antioxidant and Wound Healing

Peptide self-assembling materials have received significant attention from researchers in recent years, emerging as a popular field in biological, environmental, medical, and other new materials studies. In this study, we utilized controllable enzymatic hydrolysis technology (animal proteases) to obtain supramolecular peptide self-assembling materials (CAPs) from the Pacific oyster (Crassostrea gigas). We conducted physicochemical analyses to explore the pro-healing mechanisms of CAPs on skin wounds in both in vitro and in vivo experiments through a topical application. The results demonstrated that CAPs exhibit a pH-responsive behavior for self-assembly and consist of peptides ranging from 550 to 2300 Da in molecular weight, with peptide chain lengths of mainly 11-16 amino acids. In vitro experiments indicated that CAPs display a procoagulant effect, free radical scavenging activity, and promote the proliferation of HaCaTs (112.74% and 127.61%). Moreover, our in vivo experiments demonstrated that CAPs possess the ability to mitigate inflammation, boost fibroblast proliferation, and promote revascularization, which accelerates the epithelialization process. Consequently, a balanced collagen I/III ratio in the repaired tissue and the promotion of hair follicle regeneration were observed. With these remarkable findings, CAPs can be regarded as a natural and secure treatment option with high efficacy for skin wound healing. The potential of CAPs to be further developed for traceless skin wound healing is an exciting area for future research and development.

Effects of Replacing Fish Meal with Enzymatic Cottonseed Protein on the Growth Performance, Immunity, Antioxidation, and Intestinal Health of Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

The dietary effects of replacing fish meal with enzymatic cottonseed protein (ECP) on the growth performance, immunity, antioxidant, and intestinal health of Chinese soft-shelled turtles have not been explored. An eight-week feeding trial was conducted with a quadruplicated group of turtles (3.44 ± 0.01 g) that were randomly assigned to 16 cages (0.6 m × 0.6 m × 0.6 m) with 30 turtles that were stocked in each cage. Four dietary groups were fed with diets supplemented with 0, 2%, 4%, and 6% (ECP0 group (control group), ECP2 group, ECP4 group, ECP6 group) of enzymatic cottonseed protein replacing fishmeal. The present study illustrated that the final weight and WG in the ECP2 and ECP4 groups were significantly increased (P < 0.05) compared with the control group. The ECP2, ECP4, and ECP6 groups significantly reduced the feed coefficient (P < 0.05) and significantly increased the SGR (P < 0.05). The serum TP and ALB of the ECP4 group were significantly increased (P < 0.05). The ECP2, ECP4, and ECP6 groups significantly increased the activity of intestinal pepsin (P < 0.05), and the activity of intestinal lipase of the EPC4 group was significantly increased (P < 0.05). The intestinal villus height of the EPC4 group and EPC6 group, the villus width of the EPC2 group and EPC4 group, and the intestinal muscle thickness of the EPC4 group were significantly increased (P < 0.05). At the same time, replacing fishmeal with enzymatic cottonseed protein also affected the intestinal inflammation-related genes compared with the control group. Besides that, the expression of the IL-10 gene in the experimental group was significantly upregulated (P < 0.05). Nevertheless, the expression of TNF-α and IL-8 genes in the ECP2 group and TNF-α and IL-1β genes in the ECP4 group was significantly downregulated (P < 0.05). In summary, replacing fish meal with enzymatic cottonseed protein positively affects the growth, immunity, and intestinal health of Chinese soft-shelled turtles. The appropriate proportion of enzymatic cottonseed protein to replace fish meal in turtle feed is 4%.

Characterization of the Nonpolar and Polar Extractable Components of Glanded Cottonseed for Its Valorization

Cottonseed is the second major product of cotton (Gossypium spp.) crops after fiber. Thus, the characterization and valorization of cottonseed are important parts of cotton utilization research. In this work, the nonpolar and polar fractions of glanded (Gd) cottonseed were sequentially extracted by 100% hexane and 80% ethanol aqueous solutions and subjected to ¹³C and ¹H nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. The nonpolar (crude oil) extracts showed the characteristic NMR peak features of edible plant oils with the absence of ω-3 linolenic acid. Quantitative analysis revealed the percentage of polyunsaturated, monounsaturated, and saturated fatty acids as 48.7%, 16.9%, and 34.4%, respectively. Both general unsaturated fatty acid features and some specific olefinic compounds (e.g., oleic, linolenic, and gondonic acids) were found in the nonpolar fraction. In the polar extracts, FT-ICR MS detected 1673 formulas, with approximately 1/3 being potential phenolic compounds. Both the total and phenolic formulas fell mainly in the categories of lipid, peptide-like, carbohydrate, and lignin. A literature search and comparison further identifies some of these formulas as potential bioactive compounds. For example, one compound [2,5-dihydroxy-N'-(2,3,4-trihydroxybenzylidene) benzohydrazide] identified in the polar extracts is likely responsible for the anticancer function observed when used on human breast cancer cell lines. The chemical profile of the polar extracts provides a formulary for the exploration of bioactive component candidates derived from cottonseed for nutritive, health, and medical applications.

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.

Preparation and characterization of a solid dispersion of Hexahydrocolupulone and its application in the preservation of fresh apple juice

Hops extracts and their derivatives have many important biological activities, among them, excellent antibacterial and antioxidant properties make them a promising food preservative. However, poor water solubility limits their application in the food industry. This work aimed to improve the solubility of Hexahydrocolupulone (HHCL) by preparing solid dispersion (SD) and investigating the application of the obtained products (HHCL-SD) in actual food systems. HHCL-SD was prepared by solvent evaporation with PVPK30 as a carrier. The solubility of HHCL was dramatically increased to 24.72 mg/mL（25 ℃)by preparing HHCL-SD, much higher than that of raw HHCL (0.002 mg/mL). The structure of HHCL-SD and the interaction between HHCL and PVPK30 were analyzed. HHCL-SD was confirmed to have excellent antibacterial and antioxidant activities. Furthermore, the addition of HHCL-SD proved to be beneficial for the sensory, nutritional quality, and microbiological safety of fresh apple juice, hence prolonging its shelf-life.

Preparation, Purification, and Identification of Novel Feather Keratin-Derived Peptides with Antioxidative and Xanthine Oxidase Inhibitory Activities

Feather keratin is an underappreciated protein resource of high quality, with limited bioavailability, and it urgently requires eco-friendly methods to enhance its value. Here, we report on the preparation, purification, and identification of novel peptides with antioxidant and xanthine oxidase (XOD) inhibitory activities from fermented feather broth, using Bacillus licheniformis 8-4. Two peptides, namely, DLCRPCGPTPLA (DA-12) and ANSCNEPCVR (AR-10), displayed remarkable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging abilities with half-maximal inhibitory concentrations (IC₅₀) values of 0.048, 0.034, and 0.95, 0.84 mg/mL, respectively. These values exceed those of the previously reported feather keratin-derived antioxidant peptides. Another peptide, GNQQVHLQSQDM (GM-12), demonstrated XOD activity inhibition, with an IC₅₀ value of 12.15 mg/mL, and it quenched the fluorescence of XOD. Furthermore, after simulating gastrointestinal digestion, DA-12, AR-10, and GM-12 retained their biological activities. Meanwhile, DA-12 and GM-12 showed an unexpected synergistic inhibition on XOD activity accompanied by fluorescence quenching. This study provides new insights into the potential applications of feather keratin, including functionalized feed with antioxidative and antigout (anti-hyperuricemia) activities.

Diversity of Bioinspired Hydrogels: From Structure to Applications

Hydrogels are three-dimensional networks with a variety of structures and functions that have a remarkable ability to absorb huge amounts of water or biological fluids. They can incorporate active compounds and release them in a controlled manner. Hydrogels can also be designed to be sensitive to external stimuli: temperature, pH, ionic strength, electrical or magnetic stimuli, specific molecules, etc. Alternative methods for the development of various hydrogels have been outlined in the literature over time. Some hydrogels are toxic and therefore are avoided when obtaining biomaterials, pharmaceuticals, or therapeutic products. Nature is a permanent source of inspiration for new structures and new functionalities of more and more competitive materials. Natural compounds present a series of physico-chemical and biological characteristics suitable for biomaterials, such as biocompatibility, antimicrobial properties, biodegradability, and nontoxicity. Thus, they can generate microenvironments comparable to the intracellular or extracellular matrices in the human body. This paper discusses the main advantages of the presence of biomolecules (polysaccharides, proteins, and polypeptides) in hydrogels. Structural aspects induced by natural compounds and their specific properties are emphasized. The most suitable applications will be highlighted, including drug delivery, self-healing materials for regenerative medicine, cell culture, wound dressings, 3D bioprinting, foods, etc.

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.

Multiple Bioactivities of Peptides from Hydrolyzed Misgurnus anguillicaudatus

Misgurnus anguillicaudatus (loach) is a widely distributed benthic fish in Asia. In this study, the alkaline protease was used to hydrolyze loach, and the hydrolysate products of different molecular weights were obtained by membrane separation. In vitro antioxidant assays showed that the <3 kDa fraction (SLH-1) exhibited the strongest antioxidant activity (DPPH, hydroxyl radical and superoxide radical scavenging ability, and reducing power), while SLH-1 was purified by gel filtration chromatography, and peptide sequences were identified by LC-MS/MS. A total of six peptides with antioxidant activity were identified, namely SERDPSNIKWGDAGAQ (D-1), TVDGPSGKLWR (D-2), NDHFVKL (D-3), AFRVPTP (D-4), DAGAGIAL (D-5), and VSVVDLTVR (D-6). In vitro angiotensin-converting enzyme (ACE) inhibition assay and pancreatic cholesterol esterase (CE) inhibition assay, peptide D-4 (IC50 95.07 μg/mL, 0.12 mM) and D-2 inhibited ACE, and peptide D-2 (IC50 3.19 mg/mL, 2.62 mM), D-3, and D-6 acted as pancreatic CE inhibitors. The inhibitory mechanisms of these peptides were investigated by molecular docking. The results showed that the peptides acted by binding to the key amino acids of the catalytic domain of enzymes. These results could provide the basis for the nutritional value and promote the type of healthy products from hydrolyzed loach.

From In Silico to a Cellular Model: Molecular Docking Approach to Evaluate Antioxidant Bioactive Peptides

The increasing need to counteract the redox imbalance in chronic diseases leads to focusing research on compounds with antioxidant activity. Among natural molecules with health-promoting effects on many body functions, bioactive peptides are gaining interest. They are protein fragments of 2–20 amino acids that can be released by various mechanisms, such as gastrointestinal digestion, food processing and microbial fermentation. Recent studies report the effects of bioactive peptides in the cellular environment, and there is evidence that these compounds can exert their action by modulating specific pathways. This review focuses on the newest approaches to the structure–function correlation of the antioxidant bioactive peptides, considering their molecular mechanism, by evaluating the activation of specific signaling pathways that are linked to antioxidant systems. The correlation between the results of in silico molecular docking analysis and the effects in a cellular model was highlighted. This knowledge is fundamental in order to propose the use of bioactive peptides as ingredients in functional foods or nutraceuticals.

Identification of antioxidant peptides after digestion and absorption of isinglass by serum peptidomics and cellular antioxidant activity analysis

Isinglass, a dried product of the swim bladder, has been widely used in traditional Chinese medicine. This study attempts to identify natural antioxidant peptides after digestion and absorption of isinglass in vivo. The antioxidant effects of dietary isinglass were demonstrated by evaluating the activities of SOD, CAT and MDA contents in the mouse liver. Four novel antioxidant-related peptides (RLLWENGNLL, GSKAENPTNPGP, SPVPDLVPGSF and VPDLVPGSF) were screened based on serum peptidomics and amino acid composition. Furthermore, pretreating with four peptides significantly increased the cell viability, and SOD and CAT activities of AML12 cells with H₂O₂-mediated oxidative damage, meanwhile, significantly reduced the ROS level, MDA content and apoptosis rate and attenuated DNA damage. Therefore, it was concluded that pretreatment of the identified peptides had a protective effect on oxidatively damaged cells. This result can aid in the recognition of active peptides from isinglass consumption for potential application in nutraceuticals or functional ingredients in food.

Physicochemical, antioxidant, antimicrobial, and in vitro cytotoxic activities of corn pollen protein hydrolysates obtained by different peptidases

The applications of protein hydrolysates as food preservatives and nutraceutical ingredients have attracted much attention because of their beneficial effects. The interest in these ingredients has shifted toward their biological activities with benefits to human health. Bioactive peptides are known as antioxidant agents that could promote health-promoting effects and prolong food shelf-life beyond their basic nutritional value. Thus, the aim of this study was to investigate antioxidant, antimicrobial, and in vitro cytotoxic properties of corn pollen protein (CPP) hydrolysates obtained by different enzymes. Proteolytic activity in terms of degree of hydrolysis (DH) and SDS-PAGE analysis was measured in pancreatin (H-Pan), pepsin (H-Pep), and trypsin (H-Tri) hydrolysates. Amino acid composition, antioxidant and antimicrobial activities, and cytotoxicity of hydrolysates were evaluated. DH and SDS-PAGE revealed higher proteolytic activity of pepsin compared to other enzymes. Amino acid analysis showed that the functional amino acids such as antioxidant types were most predominant in H-Pep compared to two other samples. Antioxidant activity of hydrolysates was found to be affected by the type of enzyme and the concentration of hydrolysates. There was a significant difference (p < 0.05) between antioxidant activity of different hydrolysates. The highest antioxidant activity in terms of Trolox equivalent antioxidant capacity (0.23-2.75 mM), DPPH (33.3%-64.8%), and hydroxyl (33.7%-63.2%) radical scavenging activities, chelation of iron (33.2%-62.5%) and copper (30.2%-50.5%) metals, and total antioxidant activity (0.65-0.85) was obtained for H-Pep followed by H-Pan and H-Tri samples. Antibacterial tests showed that pepsin-hydrolyzed protein was not significantly (P > 0.05) effective against E. coli at any concentrations, however, it showed significant (P < 0.05) concentration-dependent effect against S. aureus (with inhibition zones of 15-25 mm). Cytotoxicity results revealed that CPP, as a nonhydrolyzed protein, did not generally show antiproliferative activity, however, a significant (P < 0.05) ability of H-Pep hydrolysate in decreasing HT-29 colon cancer cell line viability was seen in a concentration-dependent manner (the lowest cell viability of 32% at 5 mg/mL). Overall, investigating the application of protein-based hydrolysates is one of the possible strategies that govern their applied intentions as preservatives and nutraceuticals in the food and pharmaceutical industries.

Oxidative Stability of Cottonseed Butter Products under Accelerated Storage Conditions

Cottonseed is a natural product of cotton (Gossypium spp.) crops. This work evaluated the oxidative stability of cottonseed butters through accelerated autoxidation by storage at 60 °C for 25 days. Three oxidative stability parameter values (peroxide value, p-anisidine value, and total oxidation value) were monitored over the storage time. These chemical measurements revealed that the storage stability of the butter products was dominated by primary oxidation of lipid (oil) components, while the secondary oxidation levels were relatively unchanged over the storage time. An analysis of the tocopherols (natural oxidants in cottonseed) suggested not only the protection function of the molecules against oxidation of the cottonseed butter during storage, but also the dynamic mechanism against the primary oxidation of lipid components. Attenuated total reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR) data confirmed no changes in the major C functional groups of cottonseed butters over the storage time. On the other hand, characteristic minor peaks of conjugated dienes and trienes related to lipid oxidation were impacted by the accelerated storage. As each day of accelerated oxidation at 60 °C is equivalent to 16 days of storage at 20 °C, observations in this work should have reflected the oxidative stability behaviors of the cottonseed butters after about 13 months of shelf storage under ambient storage conditions. Thus, these data that were collected under the accelerated oxidation testing would be useful not only to create a better understanding of the autooxidation mechanism of lipid molecules in cottonseed butters, but also in developing or recommending appropriate storage conditions for cottonseed end products to prevent them from quality degradation.

Novel Antioxidant Peptides from Pearl Shell Meat Hydrolysate and Their Antioxidant Activity Mechanism

Free radicals are associated with aging and many diseases. Antioxidant peptides with good antioxidant activity and absorbability are one of the hotspots in antioxidant researches. In our study, pearl shell (Pinctada martensii) meat hydrolysate was purified, and after identification by proteomics, six novel antioxidant peptides SPSSS, SGTAV, TGVAS, GGSIT, NSVAA, and GGSLT were screened by bioinformatics analysis. The antioxidant peptides exhibited good cellular antioxidant activity (CAA) and the CAA of SGTAV (EC₅₀: 0.009 mg/mL) and SPSSS (EC₅₀: 0.027 mg/mL) were better than that of positive control GSH (EC₅₀: 0.030 mg/mL). In the AAPH-induced oxidative damage models, the antioxidant peptides significantly increased the viability of HepG2 cells, and the cell viability of SGTAV, SPSSS, and NAVAA were significantly restored from 79.41% to 107.43% and from 101.09% and 100.09%, respectively. In terms of antioxidant mechanism by molecular docking, SGTAV, SPSSS, and NAVAA could tightly bind to free radicals (DPPH and ABTS), antioxidant enzymes (CAT and SOD), and antioxidant channel protein (Keap1), suggesting that the antioxidant peptides had multiple antioxidant activities and had structure-activity linkages. This study suggests that the antioxidant peptides above are expected to become new natural materials for functional food industries, which contribute to the high-value applications of pearl shell meat.

Effects of Enzymatic Cottonseed Protein Concentrate as a Feed Protein Source on the Growth, Plasma Parameters, Liver Antioxidant Capacity and Immune Status of Largemouth Bass (Micropterus salmoides)

This study appraised the impact of enzymatic cottonseed protein concentrate (ECP) as a fish meal (FM) substitute on the growth and health of largemouth bass (Micropterus salmoides) (initial weight 14.99 ± 0.03 g). Five diets with equal nitrogen, fat, and energy were designed to replace 0%, 7.78%, 15.56%, 23.33%, and 31.11% FM by adding 0%, 3.6%, 7.2%, 10.8%, and 14.4% ECP, named ECP0, ECP3.6, ECP7.2, ECP10.8, and ECP14.4, respectively. We fed 300 fish with five experimental diets for 60 days. The results revealed that weight gain rate (WGR) and specific growth rate (SGR) did not notably reduce until the addition of ECP exceeded 7.2%. The proximate composition of fish was not affected by the amount of ECP added in diets. Plasma total protein (TP), albumin (ALB), and high-density lipoprotein (HDL) concentrations increased with the increase of ECP dosage, while the triglyceride (TG) and low-density lipoprotein (LDL) concentrations and alkaline phosphatase (ALP) activity showed an opposite trend. For hepatic antioxidant capacity, the hepatic total superoxide dismutase (T-SOD) and catalase (CAT) activities, glutathione (GSH) content, and the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase (SOD), and CAT were increased by ECP, while the hepatic malondialdehyde (MDA) content and the expression of kelch-like-ECH-associated protein 1 (Keap1) were decreased. With regard to inflammation, the expression of nuclear factor-kappa B (NF-κB), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) were inhibited by ECP. In summary, the amount of ECP added to diet can reach 7.2% to replace 15.56% FM without hampering the growth of largemouth bass, and ECP can improve the antioxidant and immune capacity.

Optimization of enzymatic hydrolysis by alcalase and flavourzyme to enhance the antioxidant properties of jasmine rice bran protein hydrolysate

This study aimed to optimize the hydrolysis conditions for producing jasmine rice bran protein hydrolysate (JBH) using response surface methodology (RSM). The independent variables were the ratio of flavourzyme to alcalase (Fl:Al; 0: 100 to 15: 85; 2.84% enzyme concentration) and hydrolysis time (60–540 min). The optimum hydrolysate was obtained at an Fl:Al ratio of 9.81: 90.19 for 60 min, since it enabled high amounts of protein, high antioxidant activity and more low molecular weight proteins. The experimental values obtained were a degree of hydrolysis (DH) of 7.18%, a protein content of 41.73%, an IC₅₀ for DPPH of 6.59 mg/mL, an IC₅₀ for ABTS of 0.99 mg/mL, FRAP of 724.81 mmol FeSO₄/100 g, and 322.35 and 479.05 mAU*s for peptides with a molecular weight of < 3 and 3–5 kDa, respectively. Using a mixture of enzymes revealed the potential of mixed enzymes to produce JBH containing more small peptides and high antioxidant activity.

Identification of Bcl2 as a Stably Expressed qPCR Reference Gene for Human Colon Cancer Cells Treated with Cottonseed-Derived Gossypol and Bioactive Extracts and Bacteria-Derived Lipopolysaccharides

Cottonseed contains many bioactive molecules including plant polyphenols. Cottonseed value might be increased by providing high-value bioactive polyphenols for improving nutrition and health. However, there was a lack of molecular evidence for cottonseed bioactivity in mammalian cells. One widely used method for evaluating the bioactivity of natural products is quantitative real-time-PCR (qPCR). The selection of stably expressed internal reference genes is a crucial task of qPCR assay for data analysis. The rationale for reference gene selection is that a lower standard deviation of the cycle of threshold (Cq) among the treatments indicates a more stable expression of the gene. The objective of this study was to select reference genes in human colon cancer cells (COLO 205) treated with cottonseed-derived gossypol and bioactive extracts along with bacterial endotoxin lipopolysaccharides (LPS). SYBR Green qPCR was used to analyze the mRNA levels of a wide range of biomarkers involved in glucose transport, lipid biosynthesis, inflammatory response, and cancer development. qPCR data (10,560 Cq values) were generated from 55 genes analyzed from 64 treatments with triplicate per treatment for each gene. The data showed that B-cell lymphoma 2 (Bcl2) mRNA was the most stable among the 55 mRNAs analyzed in the human colon cancer cells. Glyceraldehyde 3 phosphate dehydrogenase (Gapdh) and ribosome protein L32 (Rpl32) mRNAs were not good qPCR references for the colon cancer cells. These observations were consistent regardless of the treatment comparison between gossypol and LPS, glanded and glandless seed extracts, seed coat and kernel extracts, or treatment for 8 and 24 h. These results suggest that Bcl2 is a preferable reference gene for qPCR assays in human colon cancer cells treated with cottonseed-derived gossypol and bioactive extracts as well as LPS. The extensive qPCR results firmly support the conclusion that the Bcl2 gene is stably expressed at the mRNA level in the human colon cancer cells regardless of the treatment, suggesting that Bcl2 gene expression is not regulated at the mRNA level but at the post-transcriptional level. These results should facilitate studies designated to evaluate bioactivity on gene expression regulation by cottonseed molecules and other natural and synthetic molecules for nutrition and health uses.

Amino acid composition, mineral profile, free radical scavenging ability, and carbohydrase inhibitory properties of Moringa oleifera seed globulin, hydrolysates, and membrane fractions

The nutritional-amino acid profile and mineral element of Moringa oleifera seed globulin (GLO) and its hydrolysates as well as the in vitro bioactive properties-antioxidant, alpha-amylase, and alpha-glucosidase inhibition of the GLO, hydrolysates, and membrane fractions were reported. The results showed that M. oleifera contained significant amounts of essential amino acids (EAA), which are more than the minimum required by the Food and Agricultural Organization for children, except for tryptophan, which was the limiting amino acid. However, hydrolysis mostly led to a reduction in the contents of the EAA. While the process of hydrolysis and the subsequent membrane fractionation produced peptides with improved activities in 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid radical scavenging ability and oxygen radical absorbance capacity, this process produced no activities in superoxide radical scavenging ability, α-amylase, and α-glucosidase inhibitory potentials of some of the hydrolysates and peptides fractions. In summary, M. oleifera seed peptide fraction (<3 kDa) from the alcalase-derived hydrolysate contains potent antioxidants but relatively low in vitro antidiabetic properties. PRACTICAL APPLICATIONS: Several studies have established the ability of proteins, including hydrolysate and peptide fractions to provide some bioactive properties such as antioxidant, antidiabetic, anti-inflammatory among others. However, because protein functionalities are influenced by several factors such as the source, type, processing method employed among others, research has continued to evaluate the bioactivities of proteins under different conditions. In this study, therefore, we reported the impact of processing methods (hydrolysis, enzyme type, and peptide size) on the nutritional, antioxidant, and in vitro antidiabetic properties of M. oleifera seed globulin, its hydrolysates, and membrane fractions. This information plays an important role in the further exploitation of M. oleifera seed proteins in the development of functional foods and nutraceuticals.

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

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

Oxidative Stress Amelioration of Novel Peptides Extracted from Enzymatic Hydrolysates of Chinese Pecan Cake

Pecan (Carya cathayensis) is an important economic crop, and its hydrolyzed peptides have been evidenced to reduce the effect of oxidative stress due to their antioxidant capacity. Hence, the protocols of ultrafiltration and gel filtration chromatography were established to obtain bioactive peptides from by-products of C. cathayensis (pecan cake). As measured by DPPH/ABTS radical scavenging, the peptides with less molecular weight (MW) possess higher antioxidant capacity. PCPH-III (MW < 3 kDa) presented higher radical scavenging capacity than PCPH-II (3 kDa < MW < 10 kDa) and PCPH-I (MW > 10 kDa) measured by DPPH (IC50: 111.0 μg/ mL) and measured by ABTs (IC50: 402.9 μg/mL). The secondary structure and amino acid composition varied by their MW, in which PCPH-II contained more α-helices (26.71%) and β-sheets (36.96%), PCPH-III contained higher ratios of β-turns (36.87%), while the composition of different secondary of PCPH-I was even 25 ± 5.76%. The variation trend of α-helix and random experienced slightly varied from PCPH-I to PCPH-II, while significantly decreased from PCPH-II to PCPH-III. The increasing antioxidant capacity is followed by the content of proline, and PCPH-III had the highest composition (8.03%). With regard to the six peptides identified by LC-MS/MS, two of them (VYGYADK and VLFSNY) showed stronger antioxidant capacity than others. In silico molecular docking demonstrated their combining abilities with a transcription factor Kelch-like ECH-associated protein 1 (Keap1) and speculated that they inhibit oxidative stress through activating the Keap1-Nrf2-ARE pathway. Meanwhile, increased activity of SOD and CAT—antioxidant markers—were found in H2O2-induced cells. The residue of tyrosine was demonstrated to contribute the most antioxidant capacity of VYGYADK and its position affected less. This study provided a novel peptide screening and by-product utilization process that can be applied in natural product developments.