Release of antidiabetic peptides from Stichopus japonicas by simulated gastrointestinal digestion

Identification of novel α-glucosidase inhibitory peptides in Meretrix meretrix Linnaeus and their inhibitory kinetics using in silico and in vitro analyses

This study aimed to identify novel peptides with α-glucosidase inhibitory activity from Meretrix meretrix Linnaeus hydrolysates (MMLHs) following simulated gastrointestinal digestion (SGD) and to elucidate their inhibitory mechanisms. The molecular weight distribution of MMLHs progressively decreased during SGD, with hydrolysates from the intestinal digestion phase (MMLHs-I) exhibiting the strongest α-glucosidase inhibition (IC50: 0.14 ± 0.02 mg/mL). A total of 127 peptides were identified in MMLHs-I, among which 58 were unique compared to those from the gastric digestion phase. In silico screening and molecular docking identified six novel peptides-FAGDDAPR, VPLF, YRRL, WDH, PPLA, and WSG-with significant α-glucosidase inhibitory activity, displaying IC50 values of 0.90, 1.30, 1.90, 1.20, 1.00, and 1.80 mg/mL, respectively. Among them, FAGDDAPR and PPLA exhibited the highest bioactivity. Kinetic analysis and fluorescence quenching assays demonstrated that both peptides acted as mixed-type inhibitors, forming stable complexes with α-glucosidase. Their inhibitory effects were primarily driven by hydrogen bonding and hydrophobic interactions, which hindered substrate binding and induced conformational changes in the enzyme. These findings suggest that peptides derived from MMLHs through gastrointestinal digestion possess potential antidiabetic properties, highlighting their promise as functional food ingredients for mitigating hyperglycemic damage.

EPA-enriched lipid from Apostichopus japonicus byproducts mitigates UVB-induced oxidative stress and inflammation by gut-skin axis

The tremendous byproducts from sea cucumber processing discarded as waste bring serious environmental and economic challenges. The abundant EPA in sea cucumber intestines indicates the potential for lipid development. However, there is little study on how these lipids affect skin health. Using REM techniques, this study prepared lipids from Apostichopus japonicus intestines (AJIL) with a 26.63 % EPA content, which displayed DPPH scavenging capacity in vitro. Administration of AJIL showed significant skin repair effects by reducing the symptoms of UVB-induced skin tissue damage, preventing epidermal thickening and increasing hydroxyproline content to protect collagen. AJIL suppressed oxidative stress and inflammation by significantly reducing ROS and MDA levels and enhancing GPx and CAT activity, as well as inhibiting the expression of inflammatory cytokines such as TNF-α, NF-κB, IL-1β and IL-6. By upregulating Nrf2, HO-1 and NQO-1 and downregulating Keap1, AJIL activated the Keap1-Nrf2 signaling pathways. Furthermore, AJIL regulated the composition and structure of gut microbiome, especially significantly increasing the SCFA-producing and anti-inflammatory bacteria like Muribacuclaceae, Alloprevotella, Bacteroides and Prevotellaceae, then improved key metabolic pathways. Overall, AJIL mediated the gut-skin axis to prevent UVB-induced skin damage and revealed potential as a natural skin protection candidate, which transformed discarded sea cucumber intestines into valuable resources for skin health.

Exploration of ACE inhibitory peptides from sea cucumber viscera with DPP-IV inhibitory activity: Virtual screening, characterization, and potential mechanism investigation

Sea cucumber is a protein-rich food that has great potential to release bioactive compounds with diverse functionalities. Inhibition of angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) using peptides has emerged as part of new therapeutic strategy for complementing treatment of hypertension and type 2 diabetes. The present study aimed to explore novel ACE inhibitory peptides with DPP-IV inhibitory activity from sea cucumber viscera hydrolysate combining virtual screen and molecular docking approaches. Four ACE inhibitory peptides WEPFP, GFPGLP, FPGGPP, and LPPGPFP were explored from the constructed peptide database, exhibiting ACE inhibitory activity by non-competitive or competitive action modes. GFPGLP displayed the strongest activity against DPP-IV through non-competitive pattern. Human umbilical vein cell fusion cells (EA. Hy926) and insulin-resistant-HepG2 (IR-HepG2) cell model demonstrated their potential hypoglycemic and hypotensive effects on cellular functions. Network pharmacological analysis subsequently suggested that GFPGLP might exert antihypertensive and antidiabetic activity trough regulation of multiple signal pathways and interactions with commonly core targets such as TGFB1, ACE, REN, CCL2, IGF1, and PPARG. These results uncover the development of novel ACE inhibitory peptides with DPP-IV inhibitory activity and the potential action mechanism, as well as explore peptides served as functional food ingredients for management of hypertension and diabetes.

Bioactivity of Marine-Derived Peptides and Proteins: A Review

The marine environment, covering over 70% of the Earth's surface, serves as a reservoir of bioactive molecules, including peptides and proteins. Due to the unique and often extreme marine conditions, these molecules exhibit distinctive structural features and diverse functional properties, making them promising candidates for therapeutic applications. Marine-derived bioactive peptides, typically consisting of 3 to 40 amino acid residues-though most commonly, 2 to 20-are obtained from parent proteins through chemical or enzymatic hydrolysis, microbial fermentation, or gastrointestinal digestion. Like peptides, protein hydrolysates from collagen, a dominant protein of such materials, play an important role. Peptide bioactivities include antioxidant, antihypertensive, antidiabetic, antimicrobial, anti-inflammatory, anticoagulant, and anti-cancer effects as well as immunoregulatory and wound-healing activities. These peptides exert their effects through mechanisms such as enzyme inhibition, receptor modulation, and free radical scavenging, among others. Fish, algae, mollusks, crustaceans, microbes, invertebrates, and marine by-products such as skin, bones, and viscera are some of the key marine sources of bioactive proteins and peptides. The advancements in the extraction and purification processes, e.g., enzymatic hydrolysis, ultrafiltration, ion-exchange chromatography, high-performance liquid chromatography (HPLC), and molecular docking, facilitate easy identification and purification of such bioactive peptides in greater purity and activity. Despite their colossal potential, their production, scale-up, stability, and bioavailability are yet to be enhanced for industrial applications. Additional work needs to be carried out for optimal extraction processes, to unravel the mechanisms of action, and to discover novel marine sources. This review emphasizes the enormous scope of marine-derived peptides and proteins in the pharmaceutical, nutraceutical, cosmeceutical, and functional food industries, emphasizing their role in health promotion and risk reduction of chronic diseases.

Preparation and Characterization of Calcium-Chelated Sea Cucumber Ovum Hydrolysate and the Inhibitory Effect on α-Amylase

α-amylase can effectively inhibit the activity of digestive enzymes and alter nutrient absorption. The impact of ovum hydrolysates of sea cucumbers on α-amylase activity was investigated in this study. The protein hydrolysates generated using different proteases (pepsin, trypsin, and neutral protease) and molecular weights (less than 3000 and more than 3000) were investigated. The results showed that all three different hydrolysates demonstrated calcium-chelating activity and induced a fluorescence-quenching effect on α-amylase. The sea cucumber ovum hydrolysate with a molecular weight of less than 3000 Da, isolated using trypsin, showed the most effective inhibitory effect on α-amylase, with an inhibition rate of 53.9%, and the inhibition type was identified as mixed forms of inhibition. In conclusion, the generation and utilization of protein hydrolysates from sea cucumber ovum as a functional food ingredient could be a potential approach to add value to low-cost seafood by-products.

Optimization of extraction process of polysaccharide from Phylloporia fontanesiae and its simulated digestion in vitro

In this study, Phylloporia fontanesiae polysaccharide was successfully isolated through a sequential water extraction and alcohol precipitation process. Utilizing the Box-Behnken design, the extraction process was optimized based on single-factor experiments, considering variables such as the material-to-liquid ratio, extraction temperature, extraction time, and the number of extractions. The polysaccharide composition of P. fontanesiae is predominantly composed of mannose, glucuronic acid, glucose, and galactose, with a molar mass ratio of 4.31:4.10:36.83:1, along with minor amounts of aminoglucose and fucose. The polysaccharide fraction of P. fontanesiae comprises two distinct components, possessing relative molecular masses of 8.85 kDa and 134.03 kDa. Notably, the polysaccharide exhibited significant antioxidant activity. After undergoing simulated gastrointestinal digestion, no significant changes were observed in its antioxidant activity, molecular weight, or monosaccharide composition. This study not only enhanced the extraction efficiency of P. fontanesiae polysaccharide but also provided valuable insights into its composition, structure, and digestion characteristics. PRACTICAL APPLICATION: The optimum extraction process, stability, and antioxidant activity of Phylloporia fontanesiae polysaccharide during simulated digestion of gastrointestinal tract were studied. The results provide a theoretical basis for the development and application of this polysaccharide in the field of food and health products.

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.

Proteomics Analysis of the Protective Effect of Polydeoxyribonucleotide Extracted from Sea Cucumber (Apostichopus japonicus) Sperm in a Hydrogen Peroxide-Induced RAW264.7 Cell Injury Model

Sea cucumber viscera contain various naturally occurring active substances, but they are often underutilized during sea cucumber processing. Polydeoxyribonucleotide (PDRN) is an adenosine A2A receptor agonist that activates the A2A receptor to produce various biological effects. Currently, most studies on the activity of PDRN have focused on its anti-inflammatory, anti-apoptotic, and tissue repair properties, yet relatively few studies have investigated its antioxidant activity. In this study, we reported for the first time that PDRN was extracted from the sperm of Apostichopus japonicus (AJS-PDRN), and we evaluated its antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS), and hydroxyl radical scavenging assays. An in vitro injury model was established using H2O2-induced oxidative damage in RAW264.7 cells, and we investigated the protective effect of AJS-PDRN on these cells. Additionally, we explored the potential mechanism by which AJS-PDRN protects RAW264.7 cells from damage using iTRAQ proteomics analysis. The results showed that AJS-PDRN possessed excellent antioxidant activity and could significantly scavenge DPPH, ABTS, and hydroxyl radicals. In vitro antioxidant assays demonstrated that AJS-PDRN was cytoprotective and significantly enhanced the antioxidant capacity of RAW264.7 cells. The results of GO enrichment and KEGG pathway analysis indicate that the protective effects of AJS-PDRN pretreatment on RAW264.7 cells are primarily achieved through the regulation of immune and inflammatory responses, modulation of the extracellular matrix and signal transduction pathways, promotion of membrane repair, and enhancement of cellular antioxidant capacity. The results of a protein-protein interaction (PPI) network analysis indicate that AJS-PDRN reduces cellular oxidative damage by upregulating the expression of intracellular selenoprotein family members. In summary, our findings reveal that AJS-PDRN mitigates H2O2-induced oxidative damage through multiple pathways, underscoring its significant potential in the prevention and treatment of diseases caused by oxidative stress.

Antioxidant potential and protective effect of modified sea cucumber peptides against H2O2-induced oxidative damage in vitro HepG2 cells and in vivo zebrafish model

In this study, modified sea Cucumber Peptides (SCP) were prepared by reacting with xylooligosaccharide (XOS) and alginate oligosaccharides (AOS) via glycation. Free radical inhibitory and inhibition of oxidative stress of modified SCP was evaluated using human hepatocellular carcinoma (HepG2) cells and zebrafish embryos. LC-MS analysis revealed that SCPs mainly consist of 40 active peptides, with an average molecular weight of 1122.168 Da and an average length of 11 amino acid residues. For amino acid composition, L-Asparagine, L-Methionine, and L-Aspartic Acid were dominant amino acids in SCP. The result showed that the antioxidant ability of SCP against 2,2-Diphenyl-1-picrylhydrazyl (DPPH), superoxide anion radical (O-2), and Hydroxyl Radical (OH) was significantly improved after modification. In HepG2 cells, the modified SCP showed stronger protection than native SCP native against H2O2-induced oxidative stress by enhancing cell viability and reducing radical oxygen species (ROS) generation. The inhibition effect of SCP was increased after modification with XOS and AOS by 13 % and 19 % respectively. Further studies displayed that the activity of antioxidative enzymes, including Superoxide dismutase (SOD), Glutathione Peroxidase (GPx), and catalase (CAT), was remarkably enhanced, whereas malondialdehyde (MDA) level was reduced compared with native SCP and H2O2-treated groups, thus, improving the intracellular antioxidant defenses. The gene expression analysis showed that the mechanism underlying the modified SCP protective effect may be linked with the capability to regulate Nuclear factor-erythroid factor 2-related factor 2 (NRF2) gene expression. The protective effect of modified SCP against H2O2 in vitro was confirmed in vivo by reduced toxicity in zebrafish embryos via improvement of mortality rate, hatching rate, heart beating rate, and deformities of the zebrafish model. However, SCPAOS conjugate displayed greater antioxidant potentials compared to the SCPXOS, the different effects between SCPAOS and SCPXOS could be due to their different antioxidant activity. Thus, modified SCP could be potentially used as a novel nutraceutical in the preparation of anti-aging food and medicine.

Chemical substances and their activities in sea cucumber Apostichopus japonicus: A review

Apostichopus japonicus, also known as Stichopus japonicus, with medicinal and food homologous figures, is a globally recognized precious ingredient with extremely high nutritional value. There is no relevant review available through literature search, so this article selects the research articles through the keywords "sea cucumber" and "Apostichopus japonicus (Stichopus japonicus)" in six professional databases, such as Wiley, PubMed, ScienceDirect, ACS, Springer, and Web of Science, from 2000 to the present, summarizing the extraction, isolation, and purification methods for the four major categories (polysaccharides, proteins and peptides, saponins, and other components) of the A. japonicus chemical substances and 10 effective biological activities of A. japonicus. Included are anticoagulation, anticancer/antitumor activities, hematopoiesis, regulation of gut microbiota, and immune regulatory activities that correspond to traditional efficacy. Literature support is provided for the development of medicines and functional foods and related aspects that play a leading role in future directions.

Sea Cucumber Peptides Ameliorate DSS-Induced Ulcerative Colitis: The Role of the Gut Microbiota, the Intestinal Barrier, and Macrophage Polarization

The incidence of ulcerative colitis (UC) is increasing annually. There are few treatments for UC patients, and some drugs have serious side effects. Sea cucumber peptide (SCP) has anti-inflammatory, antioxidant and other biological activities, and various sea cucumber species are in pharmaceutical development. However, relevant studies on the effects of SCP on UC progression are still lacking. In this study, a mouse model of acute colitis was induced by 3% dextran sulfate (DSS), and the effect of 500 mg/kg SCP on colitis was investigated. The results showed that SCP can alleviate DSS-induced colon damage and intestinal barrier damage. SCP significantly inhibited the expression of inflammatory factors and oxidative stress in UC mice. SCP reversed the intestinal microbiota dysregulation induced by DSS, inhibited the growth of Sutterella, Prevotella_9 and Escherichia-Shigella harmful bacteria, and increased the abundance of Lachnospiraceae_NK4A136_group. At the same time, SCP treatment significantly inhibited the LPS-induced polarization of M1 macrophages, which may be mediated by two monopeptides, IPGAPGVP and TGPIGPPGSP, via FPR2. In conclusion, SCP can protect against colitis by modulating the intestinal microbiota composition and the intestinal barrier and inhibiting the polarization of M1 macrophages.

Research progress on the chemical components and biological activities of sea cucumber polypeptides

Owing to their unique physical and chemical properties and remarkable biological activities, marine biological resources are emerging as important sources of raw materials for producing health products, food, and cosmetics. Collagen accounts for approximately 70% of the sea cucumber body wall, and its hydrolysis produces small-molecule collagen polypeptides with diverse biological functions, such as anticancer, antihypertensive, immune-enhancing, memory-enhancing, and cartilage tissue repairing effects. Notably, the potential of sea cucumber polypeptides in combination with anticancer therapy has garnered considerable attention. Determining the composition and structure of sea cucumber polypeptides and exploring their structure-activity relationships will aid in obtaining an in-depth understanding of their diverse biological activities and provide scientific insights for the development and utilization of these polypeptides. Therefore, this review focuses on the amino acid structures and activities of sea cucumber polypeptides of varying molecular weights. This study also provides an overview of the biological activities of various sea cucumber polypeptides and aims to establish a scientific basis for their development.

α-Lactalbumin Peptide Asp-Gln-Trp Ameliorates Hepatic Steatosis and Oxidative Stress in Free Fatty Acids-Treated HepG2 Cells and High-Fat Diet-Induced NAFLD Mice by Activating the PPARα Pathway

SCOPE

Dietary intervention has emerged as a promising strategy for the management of nonalcoholic fatty liver disease (NAFLD). The aim of this study is to investigate the ameliorative effects of the α-lactalbumin peptide Asp-Gln-Trp (DQW) against NAFLD and the underlying mechanism.

METHODS AND RESULTS

The models of lipid metabolism disorders are established both in HepG2 cells and in C57BL/6J mice. The results demonstrate that DQW activates peroxisome proliferator-activated receptor α (PPARα) and subsequently ameliorates lipid deposition and oxidative stress in vitro. Interestingly, GW6471 markedly attenuates the modulatory effects of DQW on the PPARα pathway in HepG2 cells. Moreover, results of in vivo experiments indicate that DQW alleviates body weight gain, dyslipidemia, hepatic steatosis, and oxidative stress in high-fat-diet (HFD)-induced NAFLD mice. At the molecular level, DQW activates PPARα, subsequently enhances fatty acid β-oxidation, and reduces lipogenesis, thereby ameliorating hepatic steatosis. Meanwhile, DQW may ameliorate liver injury and oxidative stress via activating the PPARα/nuclear-factor erythroid 2 (Nrf2)/heme-oxygenase 1 (HO-1) pathway.

CONCLUSION

Those results indicate that α-lactalbumin peptide DQW may be an effective dietary supplement for alleviating NAFLD by alleviating lipid deposition and oxidative stress.

The Structural Characteristics and Bioactivity Stability of Cucumaria frondosa Intestines and Ovum Hydrolysates Obtained by Different Proteases

The study aimed to investigate the effects of alcalase, papain, flavourzyme, and neutrase on the structural characteristics and bioactivity stability of Cucumaria frondosa intestines and ovum hydrolysates (CFHs). The findings revealed that flavourzyme exhibited the highest hydrolysis rate (51.88% ± 1.87%). At pH 2.0, the solubility of hydrolysate was the lowest across all treatments, while the solubility at other pH levels was over 60%. The primary structures of hydrolysates of different proteases were similar, whereas the surface hydrophobicity of hydrolysates was influenced by the types of proteases used. The hydrolysates produced by different proteases were also analyzed for their absorption peaks and antioxidant activity. The hydrolysates of flavourzyme had β-fold absorption peaks (1637 cm^-1), while the neutrase and papain hydrolysates had N-H bending vibrations. The tertiary structure of CFHs was unfolded by different proteases, exposing the aromatic amino acids and red-shifting of the λ-peak of the hydrolysate. The alcalase hydrolysates showed better antioxidant activity in vitro and better surface hydrophobicity than the other hydrolysates. The flavourzyme hydrolysates displayed excellent antioxidant stability and pancreatic lipase inhibitory activity during gastrointestinal digestion, indicating their potential use as antioxidants in the food and pharmaceutical industries.

Protective Effect of Peptides from Pinctada Martensii Meat on the H2O2-Induced Oxidative Injured HepG2 Cells

Pinctada martensii is a major marine pearl cultured species in southern China, and its meat is rich in protein, which is an excellent material for the preparation of bioactive peptides. In this study, the peptides from Pinctada martensii meat were prepared by simulated gastrointestinal hydrolysis, and after multistep purification, the structures of the peptides were identified, followed by the solid-phase synthesis of the potential antioxidant peptides. Finally, the antioxidant activities of the peptides were verified using HepG2 cells, whose oxidative stress was induced by hydrogen peroxide (H₂O₂). It was shown that the antioxidant peptide (S4) obtained from Pinctada martensii meat could significantly increase the cell viability of HepG2 cells. S4 could also scavenge reactive oxygen species (ROS) and reduce the lactate dehydrogenase (LDH) level. In addition, it could enhance the production of glutathione (GSH) and catalase (CAT) in HepG2 cells, as well as the expression of key genes in the Nrf2 signaling pathway. Three novel antioxidant peptides, arginine-leucine (RL), arginine-glycine-leucine (RGL), and proline-arginine (PR), were also identified. In conclusion, peptides from Pinctada martensii meat and three synthetic peptides (RGL, RL, PR) showed antioxidant activity and could have the potential to be used as antioxidant candidates in functional foods.

Tandem mass tag-based quantitative proteomics analysis reveals the effects of the α-lactalbumin peptides GINY and DQW on lipid deposition and oxidative stress in HepG2 cells

The objective of this study was to investigate the mechanism by which the α-lactalbumin peptides Gly-Ile-Asn-Tyr (GINY) and Asp-Gln-Trp (DQW) ameliorate free fatty acid-induced lipid deposition in HepG2 cells. The results show that GINY and DQW reduced triglyceride, total cholesterol, and free fatty acid levels significantly in free fatty acid-treated HepG2 cells. Based on proteomic analysis, GINY and DQW alleviated lipid deposition and oxidative stress mainly through the peroxisome proliferator-activated receptor (PPAR) pathway, fatty acid metabolism, oxidative phosphorylation, and response to oxidative stress. In vitro experiments confirmed that GINY and DQW upregulated the mRNA and protein expression of fatty acid β-oxidation-related and oxidative stress-related genes, and downregulated the mRNA and protein expression of lipogenesis-related genes by activating peroxisome proliferator-activated receptor α (PPARα). Meanwhile, GINY and DQW reduced free fatty acid-induced lipid droplet accumulation and reactive oxygen species generation, and enhanced the mitochondrial membrane potential and ATP levels. Furthermore, GINY and DQW enhanced carnitine palmitoyl-transferase 1a (CPT-1a) and superoxide dismutase activities, and diminished acetyl-coenzyme A carboxylase 1 (ACC1) and fatty acid synthase (FASN) activities in a PPARα-dependent manner. Interestingly, GW6471 (a PPARα inhibitor) weakened the effects of GINY and DQW on the PPARα pathway. Hence, our findings suggest that GINY and DQW have the potential to alleviate nonalcoholic fatty liver disease by activating the PPARα pathway.

Food-derived dipeptidyl peptidase IV inhibitory peptides: Production, identification, structure-activity relationship, and their potential role in glycemic regulation

Dipeptidyl Peptidase IV (DPP-IV) inhibitory peptides are attracting increasing attention, owing to their potential role in glycemic regulation by preventing the inactivation of incretins. However, few reviews have summarized the current understanding of DPP-IV inhibitory peptides and their knowledge gaps. This paper reviews the production, identification and structure-activity relationships (SAR) of DPP-IV inhibitory peptides. Importantly, their bioavailability and hypoglycemic effects are critically discussed. Unlike the traditional method to identifying peptides after separation step by step, the bioinformatics approach identifies peptides via virtual screening that is more convenient and efficient. In addition, the bioinformatics approach was also used to investigate the SAR of peptides. Peptides with proline (Pro) or alanine (Ala) residue at the second position of N-terminal are exhibit strong DPP-IV inhibitory activity. Besides, the bioavailability of DPP-IV inhibitory peptides is related to their gastrointestinal stability and cellular permeability, and in vivo studies showed that the glucose homeostasis has been improved by these peptides. Especially, the intestinal transport of DPP-IV inhibitory peptides and cell biological assays used to evaluate their potential role in glycemic regulation are innovatively summarized. For further successful development of DPP-IV inhibitory peptides in glycemic regulation, future study should elucidate their SAR and in vivo hypoglycemic effects .

Structural characteristics and immunostimulatory activity of sea cucumber tendon polysaccharides in cyclophosphamide-induced Balb/c mice

Sea cucumber tendon, one of the main parts of sea cucumber viscera, is widely accepted as a waste residue. In this study, a sea cucumber tendon polysaccharide (SCTPII) was purified from sea cucumber tendons and its primary structures and immunomodulatory activity were investigated. SCTPII is a triple-helix conformation homogeneous polysaccharide with a molecular weight of 3.97 × 10⁶ Da that consists of glucose and fucose with molar ratios of 92.09% and 7.91% with high thermostability. In vivo tests on immunosuppressed Balb/c mice revealed that compared with the model group, the proliferation of T cells and B cells in splenic lymphocytes of mice in the high-dose group was significantly improved by 0.92 times and 5.14 times, respectively. Additionally, SCTPII could improve the proliferation ability and phagocytosis of macrophages, as well as promoting the expression of IL-6, TNF-α and IFN-γ and enhancing the intestinal physical barrier function by increasing the protein expression of claudin-1, occludin, ZO-1 and MUC2. Furthermore, the 16S rRNA sequencing of fecal samples was performed, and gene count and α-diversity analysis revealed that SCTPs could improve the microbial community richness. In particular, SCTPs could increase the relative abundance of Lactobacillus, Bacteroides and Akkermansia and reduce the relative abundance of Lachnospiraceae_NK4A136_group and Rikenellaceae_RC9_gut_group. These results demonstrate that SCPII possesses potential immunoregulatory activities in cyclophosphamide-induced mice by regulating intestinal microbiota diversity and improving immune organs, enhancing the proliferation ability of macrophages and splenocyte proliferation, and enhancing intestinal physical barrier function, which might provide important evidence for the development and utilization of the viscera of sea cucumber.

Production of Bioactive Peptides from Sea Cucumber and Its Potential Health Benefits: A Comprehensive Review

Bioactive peptides from food have been widely studied due to their potential applications as functional foods and pharmaceuticals. Sea cucumber, a traditional tonic food, is characterized by high protein and low fat, thereby substrates are being studied to release sea cucumber peptides (SCPs). Although recent studies have shown that SCPs have various bioactive functions, there is no literature reviewing the development status of SCPs. In this review, we summarized the production of SCPs, including their purification and identification, then mainly focused on the comprehensive potential health benefits of SCP in vivo and in vitro, and finally discussed the challenge facing the development of SCPs. We found that SCPs have well-documented health benefits due to their antioxidation, anti-diabetes, ACE inhibitory, immunomodulatory, anti-cancer, anti-fatigue, anti-aging, neuroprotection, micromineral-chelating, etc. However, the structure-activity relationships of SCPs and the functional molecular mechanisms underlying their regulation in vivo need further investigation. Research on the safety of SCP and its potential regulation mechanism will contribute to transferring these findings into commercial applications. Hopefully, this review could promote the development and application of SCPs in further investigation and commercialization.

Marine Products As a Promising Resource of Bioactive Peptides: Update of Extraction Strategies and Their Physiological Regulatory Effects

Marine products are a rich source of nutritional components and play important roles in promoting human health. Fish, mollusks, shellfish, as well as seaweeds are the major components of marine products with high-quality proteins. During the last several decades, bioactive peptides from marine products have gained much attention due to their diverse biological properties including antioxidant, antihypertensive, antimicrobial, antidiabetic, immunoregulation, and antifatigue. The structural characteristics of marine bioactive peptides largely determine the differences in signaling pathways that can be involved, which is also an internal mechanism to exert various physiological regulatory activities. In addition, the marine bioactive peptides may be used as ingredients in food or nutritional supplements with the function of treating or alleviating chronic diseases. This review presents an update of marine bioactive peptides with the highlights on the novel producing technologies, the physiological effects, as well as their regulation mechanisms. Challenges and problems are also discussed in this review to provide some potential directions for future research.

Roles of Dietary Bioactive Peptides in Redox Balance and Metabolic Disorders

Bioactive peptides (BPs) are fragments of 2-15 amino acid residues with biological properties. Dietary BPs derived from milk, egg, fish, soybean, corn, rice, quinoa, wheat, oat, potato, common bean, spirulina, and mussel are reported to possess beneficial effects on redox balance and metabolic disorders (obesity, diabetes, hypertension, and inflammatory bowel diseases (IBD)). Peptide length, sequence, and composition significantly affected the bioactive properties of dietary BPs. Numerous studies have demonstrated that various dietary protein-derived BPs exhibited biological activities through the modulation of various molecular mechanisms and signaling pathways, including Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2/antioxidant response element in oxidative stress; peroxisome proliferator-activated-γ, CCAAT/enhancer-binding protein-α, and sterol regulatory element binding protein 1 in obesity; insulin receptor substrate-1/phosphatidylinositol 3-kinase/protein kinase B and AMP-activated protein kinase in diabetes; angiotensin-converting enzyme inhibition in hypertension; and mitogen-activated protein kinase and nuclear factor-kappa B in IBD. This review focuses on the action of molecular mechanisms of dietary BPs and provides novel insights in the maintenance of redox balance and metabolic diseases of human.

Recent developments on production, purification and biological activity of marine peptides

Marine peptides are one of the richest sources of structurally diverse bioactive compounds and a considerable attention has been drawn towards their production and bioactivity. However, there is a paucity in consolidation of emerging trends encompassing both production techniques and biological application. Herein, we intend to review the recent advancements on different production, purification and identification technologies used for marine peptides along with presenting their potential health benefits. Bibliometric analysis revealed a growing number of scientific publications on marine peptides (268 documents per year) with both Asia (37.2%) and Europe (33.1%) being the major contributors. Extraction and purification by ultrafiltration and enzymatic hydrolysis, followed by identification by chromatographic techniques coupled with an appropriate detector could yield a high content of peptides with improved bioactivity. Moreover, the multifunctional health benefits exerted by marine peptides including anti-microbial, antioxidant, anti-hypertension, anti-diabetes and anti-cancer along with their structure-activity relationship were presented. The future perspective on marine peptide research should focus on finding improved separation and purification technologies with enhanced selectivity and resolution for obtaining more novel peptides with high yield and low cost. In addition, by employing encapsulation strategies such as nanoemulsion and nanoliposome, oral bioavailability and bioactivity of peptides can be greatly enhanced. Also, the potential health benefits that are demonstrated by in vitro and in vivo models should be validated by conducting human clinical trials for a technology transfer from bench to bedside.

Developments for Collagen Hydrolysate in Biological, Biochemical, and Biomedical Domains: A Comprehensive Review

The collagen hydrolysate, a proteinic biopeptide, is used for various key functionalities in humans and animals. Numerous reviews explained either individually or a few of following aspects: types, processes, properties, and applications. In the recent developments, various biological, biochemical, and biomedical functionalities are achieved in five aspects: process, type, species, disease, receptors. The receptors are rarely addressed in the past which are an essential stimulus to activate various biomedical and biological activities in the metabolic system of humans and animals. Furthermore, a systematic segregation of the recent developments regarding the five main aspects is not yet reported. This review presents various biological, biochemical, and biomedical functionalities achieved for each of the beforementioned five aspects using a systematic approach. The review proposes a novel three-level hierarchy that aims to associate a specific functionality to a particular aspect and its subcategory. The hierarchy also highlights various key research novelties in a categorical manner that will contribute to future research.

Structural elucidation and antidiabetic activity of fucosylated chondroitin sulfate from sea cucumber Stichopus japonicas

A fucosylated chondroitin sulfate was isolated from the body wall of sea cucumber Stichopus japonicus (FCSsj), whose structure was characterized by NMR spectroscopy and HILIC-FTMS. At the ratio of 1.00:0.26:0.65, three fucosyl residues were found: 2,4-disulfated-fucose (Fuc2,4S), 4-sulfated-fucose (Fuc4S) and 3,4-disulfated-fucose (Fuc3,4S), which were only linked to the O-3 of glucuronic acid residues (GlcA). Besides mono-fucosyl moieties, di-fucosyl branches, namely Fuc2,4Sα(1→3)Fuc4S, were also found to be attached to the O-3 of GlcA. The antidiabetic activity of FCSsj was evaluated using glucosamine induced insulin resistant (IR) Hep G2 cells in vitro. It was found that FCSsj significantly promoted the glucose uptake and glucose consumption of IR-Hep G2 cells in a dose-dependent manner, and could alleviate the cell damage. Furthermore, FCSsj could promote the glycogen synthesis in the glucosamine-induced IR-Hep G2 cells. These results provided a supplement for studying the antidiabetic activity of FCSsj.

Synthesis of difluorinated 3-oxo-N,3-diarylpropanamides from 4-arylamino coumarins mediated by Selectfluor

An expeditious approach to synthesize difluorinated 3-oxo-N,3-diarylpropanamides from 4-arylamino coumarins has been accomplished in the presence of Selectfluor, which plays the dual role of a mild oxidant and a source of fluorine.

Development of delivery system based on marine chitosan: Encapsulationand release kinetic study of antioxidant peptides from chitosan microparticle

The present work aims to encapsulate goby fish protein hydrolysate (GPH), endowed with antioxidant activity, through ionic gelation process using blue crab chitosan (CH) and tripolyphosphate anions and to evaluate the structural, thermal and antioxidant properties of the elaborated microparticles (MPs). The GPH-loaded MPs present spherical shape as seen by scanning electron microscopy (SEM) images and positive zeta potential. The increase of loaded GPH concentration led to the increase of encapsulation efficiency (EE) and to the reduction of the particle size. In fact, MPs, loaded with 2 and 5 mg/ml GPH, had EE values of 44 and 58% and mean particles size of 4.81 and 3.78 μm, respectively. Furthermore, thermogravimetric analysis (TGA) profiles revealed the enhanced thermal stability of encapsulated biopeptides compared to the free ones. Release kinetic data showed a Fickian diffusion behavior which follows swelling and a diffusion-controlled mechanism for peptides liberation. Finally, as opposed to unloaded MPs, an improvement of the antioxidant activity of the loaded MPs with biopeptides was observed.

Antidiabetic Food-Derived Peptides for Functional Feeding: Production, Functionality and In Vivo Evidences

Bioactive peptides released from the enzymatic hydrolysis of food proteins are currently a trending topic in the scientific community. Their potential as antidiabetic agents, by regulating the glycemic index, and thus to be employed in food formulation, is one of the most important functions of these peptides. In this review, we aimed to summarize the whole process that must be considered when talking about including these molecules as a bioactive ingredient. In this regard, at first, the production, purification and identification of bioactive peptides is summed up. The detailed metabolic pathways described included carbohydrate hydrolases (glucosidase and amylase) and dipeptidyl-peptidase IV inhibition, due to their importance in the food-derived peptides research field. Then, their characterization, concerning bioavailability in vitro and in situ, stability and functionality in food matrices, and ultimately, the in vivo evidence (from invertebrate animals to humans), was described. The future applicability that these molecules have due to their biological potential as functional ingredients makes them an important field of research, which could help the world population avoid suffering from several diseases, such as diabetes.