Gelatins and antioxidant peptides from Skipjack tuna (Katsuwonus pelamis) skins: Purification, characterization, and cytoprotection on ultraviolet-A injured human skin fibroblasts

Identification and characterization of novel antioxidant peptides from Yunnan dry-cured beef: A combined in silico and in vitro study

Dry-cured meats are a good natural source of bioactive peptides. However, there is limited information on the composition and antioxidant activity of peptides in Yunnan dry-cured beef (YDB). This study aimed to identify novel antioxidant peptides from YDB using peptidomics, in silico analysis, and in vitro experimental validation while predicting their antioxidant mechanism through molecular docking. A total of 541 peptides were identified in YDB, with the predominant sources being creatine kinase (13.5 %), myosin (10.4 %), and actin (7.4 %). The novel antioxidant peptides VGSYEDPYH (VH9) and FGEAAPYLRK (FK10) demonstrated a high safety profile, with a hemolysis rate of less than 5 %. Notably, VH9 exhibited excellent ABTS radical scavenging activity (IC50 = 19.698 μM), DPPH radical scavenging activity (IC50 = 1500.825 μM), and protection against oxidative stress injury in HepG2 cells. Molecular docking studies revealed that hydrogen bonding and hydrophobic interactions were the primary forces driving the binding of VH9 to the active sites of ABTS, DPPH, Keap1, and myeloperoxidase (MPO). VH9 may protect cells from oxidative damage through radical scavenging, inhibition of reactive oxygen species (ROS) generation, and modulation of the Keap1-Nrf2 antioxidant pathway. Peptides derived from YDB exhibited strong antioxidant activity and showed potential for application as natural antioxidants.

A yak bone collagen-derived antioxidant peptide with excellent stability alleviates UVA-induced photoaging by activating the Keap1/Nrf2 signaling pathway

BACKGROUND

Prolonged exposure to ultraviolet A (UVA) rays can trigger oxidative stress, leading to skin photoaging. Our team previously identified four antioxidant peptides derived from yak bone collagen through bioinformatics prediction. The objective of this study was to screen out one most promising application antioxidant peptide through molecular docking, in vitro antioxidant activity verification and stability assessment, and elucidate its mechanism of action.

RESULTS

The results of molecular docking studies suggested that GGGPPGPM (P1) could effectively bind to the key protein Keap1 in the antioxidant signaling pathway. The in vitro screening results indicated that P1 exhibited the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (83.42 ± 3.07%) and Fe2+ chelating ability (69.25 ± 6.10%) at a concentration of 1 mg mL-1. Additionally, with the exception of a few conditions, P1 retained more than 90% DPPH radical scavenging activity across a wide range of temperature, pH, metal ions and typical processing aids. Cellular results indicated that P1 significantly reduced the production of reactive oxygen species and malonaldehyde in UVA-damaged cells, and elevated the levels of superoxide dismutase and catalase. It was found that the Keap1/Nrf2 signaling pathway in the UVA-damaged photoaging cells was modulated under P1 intervention, significantly increasing the expression of NAD(P)H dehydrogenase quinone 1 and heme oxygenase-1. In addition, P1 notably enhanced the mRNA expression level of tissue inhibitor of metal protease 1 and collagen I and decreased the mRNA expression levels of matrix metalloproteinase-1.

CONCLUSION

These findings demonstrated that P1 derived from yak bone collagen presents a promising therapeutic candidate for mitigating skin photoaging. An animal model might be employed for further examination to corroborate these findings. © 2025 Society of Chemical Industry.

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

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

Hydrolyzing collagen by extracellular protease Hap of Aeromonas salmonicida: Turning chicken by-products into bioactive resources

Collagen-rich meat processing by-products have potential utilization value. Extracellular protease Hap from meat-borne Aeromonas salmonicida has been identified as an ideal protease for hydrolyzing collagen. Here, to explore the possible application of Hap for giving chicken by-products a high added value, the hydrolysis ability and mechanism were investigated. With a Vmax of 31.9 μg/mL/min and a Km of 1.18 mg/mL, Hap demonstrated obvious substrate specificity to pepsin-solubilized collagen (PSC) derived from chicken by-products, and significantly affected the tertiary structure and microstructure of PSC. Hap was found to preferentially cleave the peptide bond between Gly-X by peptide release kinetics, attacking from two ends to the middle region for α1 chain. Sixteen peptides are anticipated to be non-toxic with twenty potential biological activities at the end of hydrolysis. These observations will enrich the collagen hydrolysis mechanism of protease secreted by meat-borne bacteria and provide new insights into the utilization of meat by-products.

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.

Dynamic gastrointestinal digestion of tilapia (Oreochromis mossambicus) skin gelatin: changes of hydrolysate properties and dipeptidyl peptidase IV inhibitory activity

BACKGROUND

It is important to study the physicochemical properties of tilapia (Oreochromis mossambicus) skin gelatin and the changes in dipeptidyl peptidase IV (DPP-IV) inhibition activity during gastrointestinal digestion in order to understand and exploit the potential of tilapia as a source of DPP-IV inhibitory peptides.

RESULTS

The DPP-IV inhibition of fish-skin gelatin increased from 9.92 ± 0.76% to 36.75 ± 0.98%, and further to 51.06 ± 1.23%, following simulated intestinal digestion for a period of 60 min. After gastric digestion, the degree of hydrolysis (DH) was 18.19 ± 0.48%, the average molecular weight (AMW) was 219 ± 7.19 kDa, the sum of charged groups was -5.08 ± 0.32, and the surface hydrophobicity of the hydrolysate was 24.81 ± 0.25. After intestinal digestion, these values changed to 27.72 ± 0.47%, 146.56 ± 8.16 kDa, -8.09 ± 0.32, and 13.04 ± 0.53, respectively. The DH and sum of charged groups exhibited positive correlations with DPP-IV inhibition (0.94 and 0.71, respectively), but AMW showed a negative correlation (-0.96). MATLAB fit functions were applied to predict theoretical inhibition values, with the fitted equation: DPP-IV inhibition = 2.5885 × DH - 0.0983 × AMW - 1.0047 × sum of charged groups + 3.5118. The test set for the multiple linear regression model demonstrated an R2 equal to or greater than 0.8.

CONCLUSION

The DH, AMW, and sum of charged groups in the hydrolysate correlated with DPP-IV inhibition, and the fitted equation predicted DPP-IV inhibition effectively in tilapia skin gelatin. © 2024 Society of Chemical Industry.

Physiochemical and functional properties of gelatin obtained from frigate mackerel (Auxis thazard), skipjack tuna (Katsuwonus pelamis), Longtail tuna (Thunnus tonggol) and yellowfin tuna (Thunnus albacares) skin

This study conducted a systematic investigation into the physicochemical and functional properties of gelatin extracted through alkaline methods from the skins of four commercially significant tuna species: frigate mackerel (Auxis thazard), skipjack tuna (Katsuwonus pelamis), longtail tuna (Thunnus tonggol), and yellowfin tuna (Thunnus albacares). Comparative analyses revealed notable species-specific variations in gelatin yield, amino acid composition, molecular weight distribution, and functional performance. Notably, yellowfin tuna skin gelatin (YSG) exhibited the highest melting point (28.09 °C), gel strength (271 g), and proline content (14.3 %), along with superior foaming capacity (20.43 %), water retention, and emulsification stability. Molecular weight profiles obtained via SDS-PAGE confirmed the presence of α- and β-chains characteristic of type I collagen, with YSG demonstrating enhanced structural integrity and thermal stability attributed to its elevated proline content. Additionally, Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD) analyses indicated stronger hydrogen bonding and preservation of the triple-helix structure in YSG. While longtail tuna yielded the highest extraction rate (21.5 %), skipjack tuna showed the highest protein content (86.7 %). In contrast, frigate mackerel gelatin displayed darker coloration (ΔE* = 53.09) due to residual pigments. Rheological assessments highlighted YSG's optimal viscoelasticity and melting behavior, aligning with its robust interfacial properties. These findings underscore the potential of yellowfin tuna skin gelatin as a viable alternative to mammalian gelatin in food and biomedical applications, offering enhanced functional performance while valorizing underutilized fishery by-products.

Development and characterization of gelatin peptides and peptide‑calcium chelates from tuna processing by-products of skins and bones

This study used hydrothermal extraction to obtain gelatin from tuna processing by-products. After treatment, the yield (w/w dry weight) of gelatin from skins and bones were 70.22 ± 2.07 % and 28 ± 3.03 %, respectively. Enzymatic hydrolysis using alkaline protease and pancreatin converted the gelatins into peptides, with the content of oligopeptide up to 87.67 ± 1.44 %. The tuna bone gelatin peptides exhibiting higher scavenging abilities against hydroxyl radicals (·OH-), 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH·), and hydrogen peroxide (H2O2) compared to tuna skin gelatin peptides. Gelatin peptides were chelated with CaCl2 at 50 °C for 60 min, pH 8.0, and a 1:2 peptide-to‑calcium ratio, achieving a maximum calcium binding capacity of 56.70 ± 1.67 %. Fourier-transform infrared spectroscopy indicated the participation of amino and carboxyl groups in the reaction. These findings provide technical and theoretical support for the development of calcium-chelated gelatin peptides.

Isolation and Characterisation of Acid Soluble Collagens and Pepsin Soluble Collagens from Eel (Anguilla japonica Temminck et Schlegel) Skin and Bone

Eel (Anguilla japonica) is an important and valuable food fish in East Asia and its by-products have been reported to include bioactive and profitable components. This study aimed to extract, characterise, and compare the structure and properties of acid-soluble collagens (ASCs) and pepsin-soluble collagens (PSCs) from the skin and bone of eel (Anguilla japonica), providing insights into their composition, structure, and properties for various applications. The yields of ASC-S (from skin), PSC-S (from skin), ASC-B (from bone), and PSC-B (from bone) were 12.16%, 15.54%, 0.79%, and 1.34% on a dry weight basis, respectively. Glycine, the dominant amino acid, accounted for 16.66% to 22.67% of total amino acids in all samples. SDS-PAGE and FTIR analyses showed the typical triple-helical structure of type I collagen with slight variations in molecular order in extract and intermolecular cross-linking between skin and bone collagens. The denaturation temperature (Tmax1) measured by differential scanning calorimetry (DSC) is 81.39 °C and 74.34 °C, respectively, for ASC-B and ASC-S. Bone collagen has higher thermal resistance than skin collagen. Surface morphology imaged using a scanning electron microscope (SEM) showed that the bone collagen had a denser network structure, whilst the skin collagen was more fibrous and porous. The findings suggest that eel-derived collagens from skin and bone can serve as potential alternatives in the food, cosmetic, and healthcare industries.

Antioxidant Peptides from Miiuy Croaker Swim Bladders: Ameliorating Effect and Mechanism in NAFLD Cell Model through Regulation of Hypolipidemic and Antioxidant Capacity

In this work, the hypolipidemic and antioxidative capacity of FSGLR (S7) and GIEWA (S10) from miiuy croaker swim bladders was explored systematically in an oleic acid (OA)-induced nonalcoholic fatty liver disease (NAFLD) model of HepG2 cells. Moreover, the hypolipidemic activity of S7 and S10 and their antioxidative abilities were preliminarily investigated in combination with molecular docking technology. The results indicated that S7 and S10 could decrease the amount of lipid accumulation and the content of triglycerides (TG) and total cholesterol (TC) in the OA-induced NAFLD cell model in a dose-dependent manner. In addition, S7 and S10 exhibited better bile salt binding, pancreatic lipase (PL) inhibition, and cholesterol esterase (CE) inhibition capacities. The hypolipidemic mechanisms of S7 and S10 were connected with the downregulation of the mRNA expression levels of adipogenic factors, including sterol-regulatory element-binding protein-1c (SREBP-1c), acetyl-CoA carboxylase (ACC), sterol-regulatory element-binding protein (SREBP)-2, hydroxymethylglutaryl-CoA reductase (HMGR), and fatty acid synthase (FAS) (p < 0.01), and the upregulation of the mRNA expression of β-oxidation-related factors, including carnitine palmitoyltransferase 1 (CPT-1), acyl-CoA oxidase 1 (ACOX-1), and peroxisome proliferator-activated receptor α (PPARα). Moreover, FSGLR (S7) and GIEWA (S10) could significantly protect HepG2 cells against OA-induced oxidative damage, and their antioxidant mechanisms were related to the increased activity of intracellular antioxidant proteases (superoxide dismutase, SOD; glutathione peroxidase, GSH-PX; catalase, CAT) to remove excess reactive oxygen species (ROS) and decrease the production of malondialdehyde (MDA). The presented findings indicate that the hypolipidemic and antioxidant functions and mechanisms of S7 and S10 could make them potential hypolipidemic and antioxidant candidates for the treatment of NAFLD.

Characterizing the Ultraviolet (UV) Screening Ability of L-5-Sulfanylhistidine Derivatives on Human Dermal Fibroblasts

Using sunscreens is one of the most widespread measures to protect human skin from sun ultraviolet radiation (UVR) damage. However, several studies have highlighted the toxicity of certain inorganic and organic UV filters used in sunscreens for the marine environment and human health. An alternative strategy may involve the use of natural products of marine origin to counteract UVR-mediated damage. Ovothiols are sulfur-containing amino acids produced by marine invertebrates, microalgae, and bacteria, endowed with unique antioxidant and UV-absorption properties. This study aimed to evaluate the protective effect of synthetic L-5-sulfanyl histidine derivatives, inspired by natural ovothiols, on human dermal fibroblasts (HDFs) upon UVA exposure. By using a custom-made experimental set-up to assess the UV screening ability, we measured the levels of cytosolic and mitochondrial reactive oxygen species (ROS), as well as cell viability and apoptosis in HDFs, in the presence of tested compounds, after UVA exposure, using flow cytometry assays with specific fluorescent probes. The results show that L-5-sulfanyl histidine derivatives display a UV screening capacity and prevent loss in cell viability, the production of cytosolic and mitochondrial ROS induced by UVA exposure in HDFs, and subsequent apoptosis. Overall, this study sheds light on the potential applications of marine-inspired sulfur-containing amino acids in developing alternative eco-safe sunscreens for UVR skin protection.

Bioactive Molecules from the Invasive Blue Crab Callinectes sapidus Exoskeleton: Evaluation of Reducing, Radical Scavenging, and Antitumor Activities

In recent years, the invasive Atlantic blue crab (Callinectes sapidus) has increased its spread throughout the Mediterranean Sea, threatening native biodiversity and local economies. This study aimed to valorize C. sapidus sampled in Sicily by utilizing its exoskeleton as a source of chitosan, astaxanthin, and bio-phenolic compounds. These biomolecules were evaluated for their reducing, radical scavenging, and antitumor activity. The ferric ion reducing antioxidant power (FRAP) and the free radical scavenging activity against radical 2,2-Diphenyl-1-picrylhydrazyl (DPPH) were significantly higher for chitosan (3.16 ± 0.10 mg AAE/g and 8.1 ± 0.10 µmol TE/g). No significant differences were observed among the tested biomolecules in their activity in scavenging the radical 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Both bio-phenolic compounds and astaxanthin exhibited dose-dependent cytotoxicity on CaCo-2 (IC50 = 12.47 and 18 µg/mL) and HepG2 (IC50 = 10.25 and 1.26 µg/mL) cell lines, while only bio-phenols showed no cytotoxic effect on differentiated CaCo-2 cells up to 20 µg/mL. These findings highlight the value of blue crab by-products in supporting a circular economy, offering a sustainable approach to managing this invasive species while providing bioactive compounds with promising medical and nutraceutical applications.

Optimization of enzymatic production of anti-skin aging biopeptides from white sorghum [Sorghum bicolor (L) Moench] grain

Recently, kafirins from white sorghum [Sorghum bicolor (L) Moench] grain have shown promise as a source of biopeptides with anti-skin aging effects (anti-inflammatory, antioxidant, and inhibition of photoaging-associated enzymes). This study employed response surface methodology (RSM) to optimize the extraction and enzymatic hydrolysis of kafirins (KAF) for the production of peptides with anti-skin aging properties. The optimization of conditions (reaction time and enzyme/substrate ratio) for liquefaction with α-amylase and hydrolysis of KAF with alcalase was performed using 32 complete factorial designs. Subsequently, ultrafiltered peptide extracts were obtained with molecular weights of 1-3 kDa (KAF-UF3) and lower than 1 kDa (KAF-UF1), which mainly contain hydrophobic amino acids (proline, leucine, isoleucine, phenylalanine, and valine) and peptide fractions with molecular weights of 0.69, 1.14, and 1.87 kDa. Consequently, the peptide extracts protected immortalized human keratinocytes (HaCaT cells) from ultraviolet B radiation (UVB)-induced damage by preventing the decrease and/or restoring the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px)]. Furthermore, KAF-UF3 and KAF-UF1 inhibited (20-29%) elastase and collagenase overactivity in UVB-exposed murine fibroblasts (3T3 cells). Thus, KAF-UF3 and KAF-UF1 exhibited behavior similar to that observed with glutathione (GSH), suggesting their potential as functional peptide ingredients in skincare products.

Comparison of Microalgae Nannochloropsis oceanica and Chlorococcum amblystomatis Lipid Extracts Effects on UVA-Induced Changes in Human Skin Fibroblasts Proteome

Lipid extracts from the microalgae Nannochloropsis oceanica and Chlorococcum amblystomatis have great potential to prevent ultraviolet A (UVA)-induced metabolic disorders. Therefore, the aim of this study has been to analyze their cytoprotective effect, focused on maintaining intracellular redox balance and inflammation in UVA-irradiated skin fibroblasts, at the proteome level. The above lipid extracts reversed the suppression of the antioxidant response caused by UVA radiation, which was more visible in the case of C. amblystomatis. Modulations of interactions between heme oxygenase-1 and matrix metalloproteinase 1/Parkinson's disease protein 7/transcript1-α/β, as well as thioredoxin and migration inhibitory factor/Parkinson's disease protein 7/calnexin/ATPase p97, created key molecular signaling underlying their cytoprotective actions. Moreover, they reduced pro-inflammatory processes in the control group but they also showed the potential to regulate the cellular inflammatory response by changing inflammasome signaling associated with the changes in the caspase-1 interaction area, including heat shock proteins HSP90, HSPA8, and vimentin. Therefore, lipid extracts from N. oceanica and C. amblystomatis protect skin fibroblast metabolism from UVA-induced damage by restoring the redox balance and regulating inflammatory signaling pathways. Thus, those extracts have proven to have great potential to be used in cosmetic or cosmeceutical products to protect the skin against the effects of solar radiation. However, the possibility of their use requires the evaluation of their effects at the skin level in in vivo and clinical studies.

Preparation and identification of novel antioxidant peptides from collagen hydrolysate of sheep hoof assisted by ultrasound

In this study, different ultrasound-assisted modes [ultrasonic simultaneous (US) and ultrasonic preconditioning (UP)] of synergistic enzymatic hydrolysis were used to prepare bioactive peptides of sheep hoof collagen. The 2, 2-diphenyl - 1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2 '-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity and metal chelating capacity of sheep's hoof collagen antioxidant peptides (SCPs) (at 1 mg/mL) prepared at 20 min of treatment in US treatment mode (US-20) were 48.56 ± 0.68 %, 51.97 ± 1.15 % and 65.58 ± 1.36 %, respectively, which were higher compared with the control and UP groups. Using LC-MS/MS analysis, 9336, 11,527, and 11,909 peptide sequences were identified from collagen hydrolysate by C, UP-20, and US-20, respectively. The peptides ACEDAPPSAAHFR and FGFEVGPACFLG with high bioactivity were screened using computer analysis. Molecular docking results revealed that hydrogen bonding and hydrophobic interactions between the two peptide sequences with DPPH and ABTS radicals may be responsible for their antioxidant properties. Therefore, we have optimized the extraction of bioactive peptides from sheep hoof collagen using ultrasound-assisted enzymatic hydrolysis, which is helpful for the high-value utilisation of sheep hoof by-products and the extraction of foodborne antioxidant peptides.

Chitosan-collagen biopolymer biofilm derived from cephalopod gladius; Evaluation of osteogenesis, angiogenesis and wound healing for tissue engineering application

Chitosan (Ch) and acid-soluble collagen (ASC) from Doryteuthis singhalensis gladius were isolated to test their osteogenic, angiogenic, and wound healing capabilities in male Wistar rats. The results of the study showed that the ASC yield was 18.58 %, the total protein content was 86.43 % ± 0.18 %, and the amino acid composition was as follows: glycine, 15.68 %; proline, 13.84 %. A, B, I, II, and III show FT-IR amide regional bands at 3392, 2959, 1652, 1471, and 1237 cm-1 respectively. The electrophoretic pattern of ASC validated its molecular weights of 105 kDa and 96 kDa. The 1H NMR spectra showed pure singles at 1.99 ppm, and the UV-Vis spectrum showed a particular absorbance between 238 and 220 nm. The DSC showed two endothermic peaks: one with an To value of 119.72 °C and TP of 126.28 °C, and the other with 147.42 °C and 148.47 °C. Initially, we fabricated Ch and ASC biofilms at an 8.5:1.5 ratio for tissue engineering applications. A cellular-level study demonstrated good biocompatibility and enhanced osteoblastic differentiation of collagen chitosan films (CChF). Additionally, the biofilm exhibited increased angiogenic potency, as observed in the chick embryo chorioallantoic membrane (CAM) assay. The experimental animal model demonstrated that in wound healing, the CChF treated rats (95.75 ± 2.28 %) had a greater decrease in the diameter of the wound than the control rats (22.25 ± 2.45 %), followed by the CF (collagen film) treated rats (63.25 ± 2.08 %) and ChF (chitosan film) (52.67 ± 1.58 %). Rats treated with CChF had 48.82 ± 1.25 mg/g of hydroxyproline in NFGT and 75.25 ± 1.56 mg/g of overall protein. The higher hydroxyproline levels in the CChF-treated groups corroborated these histopathological findings. These results imply that by promoting the development of scars, inflammation, and proliferation, CChF accelerates the healing process.

Structural, antioxidant activity, and stability studies of jellyfish collagen peptide-calcium chelates

The aim of this study was to prepare and characterize jellyfish collagen peptide (JCP)-calcium chelates (JCP-Ca) using peptides with different molecular weights. Further analysis revealed that the low-molecular-weight jellyfish collagen peptide (JCP1) had a higher chelation rate. Structural characterization showed that functional groups such as N-H, C[bond, double bond]O, and -COO were involved in the formation of JCP-Ca, which shifted towards a more ordered and regular structure, and smaller-molecular-weight peptides were more likely to form a denser structure. In addition, JCPs chelated with calcium ions showed excellent antioxidant capacity. JCP-Ca showed good stability in heat-treated and gastrointestinal environments, whereas the antioxidant activity was significantly reduced under highly acidic conditions. The present study addresses the knowledge gap regarding the physicochemical properties of JCP-Ca and establishes a solid research foundation for its associated products.

Materials based on biodegradable polymers chitosan/gelatin: a review of potential applications

Increased mass manufacturing and the pervasive use of plastics in many facets of daily life have had detrimental effects on the environment. As a result, these worries heighten the possibility of climate change due to the carbon dioxide emissions from burning conventional, non-biodegradable polymers. Accordingly, biodegradable gelatin and chitosan polymers are being created as a sustainable substitute for non-biodegradable polymeric materials in various applications. Chitosan is the only naturally occurring cationic alkaline polysaccharide, a well-known edible polymer derived from chitin. The biological activities of chitosan, such as its antioxidant, anticancer, and antimicrobial qualities, have recently piqued the interest of researchers. Similarly, gelatin is a naturally occurring polymer derived from the hydrolytic breakdown of collagen protein and offers various medicinal advantages owing to its unique amino acid composition. In this review, we present an overview of recent studies focusing on applying chitosan and gelatin polymers in various fields. These include using gelatin and chitosan as food packaging, antioxidants and antimicrobial properties, properties encapsulating biologically active substances, tissue engineering, microencapsulation technology, water treatment, and drug delivery. This review emphasizes the significance of investigating sustainable options for non-biodegradable plastics. It showcases the diverse uses of gelatin and chitosan polymers in tackling environmental issues and driving progress across different industries.

Absorption of bioactive peptides following collagen hydrolysate intake: a randomized, double-blind crossover study in healthy individuals

Background

Collagen hydrolysates (CH) in functional foods and supplements are dietary sources of amino acids (AAs) and di-and tripeptides linked to various health benefits. This study aimed to investigate the single-dose bioavailability of skin- and hide-derived CH from fish, porcine and bovine origin with different molecular weights (bovine 2,000 and 5,000 Da).

Methods

A randomized, double-blind crossover clinical study was performed with healthy volunteers assessing the plasma concentration of free and peptide-bound hydroxyproline (Hyp) as well as selected peptides reported to be abundantly present in collagen.

Results

The pharmacokinetic endpoints demonstrated comparable uptake of free Hyp from all CH. A higher amount of total compared to free Hyp indicated the uptake of substantial amounts of Hyp-containing di- or tripeptides.

Conclusion

Independently of source and molecular weight, all CH yielded relevant plasma concentrations of the investigated metabolites. Larger studies are needed to estimate an ideal level of selected circulating metabolites needed to trigger distinct physiological reactions in target tissues.

A Na+ channel receptor of FMRFamide in the cephalopod Sepiella japonica: Identification, characterisation, and expression profiling during different stages of gonadal development

FMRFamide, a member of the neuropeptide family, is involved in numerous physiological processes. FMRFamide-activated sodium channels (FaNaCs) are a family of non-voltage-gated, amiloride-sensitive, Na+-selective channels triggered by the neuropeptide FMRFamide. In the present study, the full-length cDNA of the FaNaC receptor of Sepiella japonica (SjFaNaC) was cloned. The cDNA of SjFaNaC was 3004 bp long with an open reading frame (ORF) of 1812 bp, encoding 603 amino acid residues with no signal peptide at the N-terminus. Sequence analysis indicated that SjFaNaC shared a high identity with other cephalopods FaNaCs and formed a sister clade with bivalves. The protein structure was predicted using SWISS-MODEL with AcFaNaC as the template. Quantitative real-time PCR (qRT-PCR) revealed that SjFaNaC transcripts were highly expressed in both female and male reproductive organs, as well as in the optic lobe and brain of the central nervous system (CNS). Results of in situ hybridisation (ISH) showed that SjFaNaC mRNA was mainly distributed in the medulla and deep retina of the optic lobe and in both the supraesophageal and subesophageal masses of the brain. Subcellular localisation indicated that the SjFaNaC protein was localised intracellularly and on the cell surface of HEK293T cells. In summary, these findings may lay the foundation for future exploration of the functions of SjFaNaC in cephalopods.

Marine Antioxidants from Marine Collagen and Collagen Peptides with Nutraceuticals Applications: A Review

Collagen peptides and marine collagen are enormous resources currently utilized. This review aims to examine the scientific literature to determine which collagen peptides derived from marine sources and which natural active antioxidants from marine collagen have significant biological effects as health-promoting nutraceuticals. Marine collagen is extracted from both vertebrate and invertebrate marine creatures. For vertebrates, this includes fish skin, bones, scales, fins, and cartilage. For invertebrates, it includes mollusks, echinoderms, crustaceans, and poriferans. The method used involved data analysis to organize information for isolating and identifying marine biocompounds with antioxidant properties. Specifically, amino acids with antioxidant properties were identified, enabling the use of hydrolysates and collagen peptides as natural antioxidant nutraceuticals. The methods of extraction of hydrolyzed collagen and collagen peptides by different treatments are systematized. The structural characteristics of collagen, collagen peptides, and amino acids in fish skin and by-products, as well as in invertebrate organisms (jellyfish, mollusks, and crustaceans), are described. The antioxidant properties of different methods of collagen hydrolysates and collagen peptides are systematized, and the results are comparatively analyzed. Their use as natural antioxidant nutraceuticals expands the range of possibilities for the exploitation of natural resources that have not been widely used until now.

Unraveling the biological potential of chicken viscera proteins: a study based on their enzymatic hydrolysis to obtain hydrolysates with antioxidant properties

Chicken meat production has increased over the years, leading to a proportional increase in waste generation, which often contains high levels of proteins, such as viscera. Therefore, this study aimed to investigate the enzymatic hydrolysis of chicken viscera proteins as a strategy to value solid waste from the poultry industry. The hydrolysates were characterized for their antioxidant properties and molecular weight distribution. Additionally, the enzymatic hydrolysis process was scaled up from 125 mL flasks with 50 mL of protein solution to 3 L using a 6 L bioreactor. The enzymatic hydrolysis of chicken viscera proteins using a binary mixture of proteases (85.25 U/mL of each enzyme, Alcalase and Flavourzyme, totaling 170.5 U/mL) resulted in an increase of up to 245% in 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, 353% 2,2-diphenyl-1-picryl-hydrazyl (DPPH) in radical scavenging, 69% in Ferric Reducing Antioxidant Power Assay (FRAP) and 146% in total reducing capacity (TRC). The antioxidant properties of the protein hydrolysates are preserved during the scale-up of enzymatic hydrolysis. Protein fractions smaller than 5 kDa showed the highest ABTS and DPPH radical scavenging activities, while fractions greater than 30 kDa showed the best results for the FRAP method.

Unlocking the potential of chicken liver byproducts: Identification of antioxidant peptides through in silico approaches and anti-aging effects of a selected peptide in Caenorhabditis elegans

Chicken meat processing generates a substantial number of byproducts, which are either underutilized or improperly disposed. In this study, we employed in silico approaches to identify antioxidant peptides in chicken liver byproducts. Notably, the peptide WYR exhibited remarkable 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activity with an IC50 of 0.13 ± 0.01 mg/mL and demonstrated stability under various conditions, including thermal, pH, NaCl, and simulated gastrointestinal digestion. Molecular docking analysis revealed significant hydrogen bonding interactions, while molecular dynamics showed differential stability with ABTS and 2,2-Diphenyl-1-picrylhydrazyl (DPPH). WYR exhibited improved stress resistance, decreased levels of reactive oxygen species (ROS), elevated the activities of superoxide dismutase (SOD) and catalase (CAT), and modulated the expression of crucial genes through the insulin/insulin-like growth factor (IIS) signaling pathway, mitogen-activated protein kinase (MAPK), and heat shock transcription factor-1 (HSF-1) pathways. These effects collectively contributed to the extension of Caenorhabditis elegans' lifespan. This study not only provides an effective method for antioxidant peptide analysis but also highlights the potential for enhancing the utilization of poultry byproducts.

Extraction, Physicochemical Properties, and In Vitro Antioxidant Activities of Chondroitin Sulfate from Bovine Nose Cartilage

Beef is an important high-nutrition livestock product, and several byproducts, such as bovine cartilage, are produced during slaughter. To effectively utilize these agricultural and pastoral byproducts, combined (trypsin-papain) enzymolysis and cetylpyridine chloride purification methods were used to obtain chondroitin sulfate (CS) from the nasal cartilage of Shaanxi Yellow cattle. The effects of pH, temperature, and time on the CS yield during enzymatic hydrolysis were investigated, and the CS extraction process was optimized using response surface methodology. The best yield of CS was 21.62% under the optimum conditions of pH 6.51, temperature of 64.53°C, and enzymolysis time of 19.86 h. The molecular weight of CS from Shaanxi cattle nasal cartilage was 89.21 kDa, glucuronic acid content was 31.76 ± 0.72%, protein content was 1.12 ± 0.03%, and sulfate group content was 23.34 ± 0.08%. The nasal cartilage CS of the Yellow cattle showed strong DPPH•, •OH, and ABTS+• radical scavenging abilities and ferrous reduction ability in the experimental concentration range. This study could contribute to "turn waste into treasure" and improve the comprehensive utilization of regional characteristic biological resources.

Advances in Research on the Activity Evaluation, Mechanism and Structure-Activity Relationships of Natural Antioxidant Peptides

Antioxidant peptides are a class of biologically active peptides with low molecular weights and stable antioxidant properties that are isolated from proteins. In this review, the progress in research on the activity evaluation, action mechanism, and structure-activity relationships of natural antioxidant peptides are summarized. The methods used to evaluate antioxidant activity are mainly classified into three categories: in vitro chemical, in vitro cellular, and in vivo animal methods. Also, the biological effects produced by these three methods are listed: the scavenging of free radicals, chelation of metal ions, inhibition of lipid peroxidation, inhibition of oxidative enzyme activities, and activation of antioxidant enzymes and non-enzymatic systems. The antioxidant effects of natural peptides primarily consist of the regulation of redox signaling pathways, which includes activation of the Nrf2 pathway and the inhibition of the NF-κB pathway. The structure-activity relationships of the antioxidant peptides are investigated, including the effects of peptide molecular weight, amino acid composition and sequence, and secondary structure on antioxidant activity. In addition, four computer-assisted methods (molecular docking, molecular dynamics simulation, quantum chemical calculations, and the determination of quantitative structure-activity relationships) for analyzing the structure-activity effects of natural peptides are summarized. Thus, this review lays a theoretical foundation for the development of new antioxidants, nutraceuticals, and cosmetics.

Purification, identification and molecular docking of dual-functional peptides derived from corn protein hydrolysates with antioxidant and antiadhesive activity against Helicobacter pylori

BACKGROUND

More than 50% of the world's population is infected with Helicobacter pylori, which is classified as a group I carcinogen by the World Health Organization (WHO).

RESULTS

Corn protein dual-functional peptides were identified and functionally analyzed in vitro and in silico. Two novel dual-functional peptides were identified as Cys-Gln-Asp-Val-Pro-Leu-Leu (CQDVPLL, CQ7) and Thr-Ile-Phe-Pro-Gln-Cys (TIFPQC, TI6) using nanoscale liquid chromatography coupled to tandem mass spectrometry (nano-LC-MS/MS). The antiadhesive effects against H. pylori of CQ7 and TI6 were 45.17 ± 2.41% and 48.62 ± 1.84% at 4 mg mL-1 , respectively. In silico prediction showed that CQ7 and TI6 had good physicochemical properties. Molecular docking demonstrated that CQ7 and TI6 could bind to the adhesins BabA and SabA by hydrophobic interactions and hydrogen bonds, preventing H. pylori infection. Moreover, CQ7 showed strong antioxidant activity due to its unique amino acid composition.

CONCLUSION

The present study demonstrated that the identified peptides, CQ7 and TI6, possess antioxidant and antiadhesive effects, preventing H. pylori infection and alleviating oxidative injury to the gastric mucosa. © 2023 Society of Chemical Industry.

α-Mangostin suppresses ethanol-induced gastric ulceration by regulating the Nrf2/HO-1 and NF-κB/NLRP3/caspase-1 signaling pathways and gut microbiota

α-Mangostin is a natural xanthone derivative isolated from Camellia atrophy (CA), commonly known as Lichuan black tea (LBT). The present study investigated the ameliorating effect and mechanism of α-mangostin on alcoholic gastric ulcers (GU) in rats. In vivo, α-mangostin relieved pathological symptoms. Moreover, α-mangostin regulated the activation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase 1 (HO-1) and nuclear factor κB (NF-κB)/NLR family pyrin domain containing 3 (NLRP3)/caspase-1 pathways. Reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were significantly decreased and IL-10 were increased, the microtubule-associated protein light chain 3 (LC3)-II/LC3-I ratio was increased, p62 protein expression was decreased, and inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) protein expression was down-regulated. The relevant mechanisms were validated using GSE-1 and RAW264.7 cells in an in vitro model. Furthermore, α-mangostin increased Ligilactobacillus and Muribaculum abundance as well as propionic acid and butyric acid contents. Therefore, α-mangostin possesses antioxidant and anti-inflammatory properties, and remodels intestinal flora dysbiosis through mechanisms that may involve regulation of the Nrf2/HO-1 pathway and NF-κB/NLRP3/caspase-1 pathway. It also increases propionic acid and butyric acid contents. This study provides novel evidence regarding the use of α-mangostin for treating GU.

Physicochemical and thermal properties of pepsin- and acid-soluble collagen isolated from the body wall of sea cucumbers (Stichopus hermanni)

The main objective of this work was to characterize the acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from the body wall of the sea cucumber scientifically called, Stichopus hermanni. For the extraction of ASC and PSC, the pre-treated sea cucumber body walls were subjected to 0.5 M acetic acid and 5 g L-1 pepsin, respectively. The yield of ASC (7.30% ± 0.30%) was found to be lower than the PSC (23.66% ± 0.15%), despite both ASC and PSC having similar chemical compositions except for the quantity of protein. The collagens produced from ASC and PSC show maximum peaks on ultraviolet-visible spectroscopic profiles at wavelengths of 230 and 235 nm, respectively, with no significant difference in the maximum temperature (Tmax ) of the extracted ASC and PSC. The ASC's coloration was whiter than that of the PSC. As a result, the collagen obtained from the body wall of the sea cucumber showed promise for usage as a substitute for collagen derived from marine sources. PRACTICAL APPLICATION: The two most popular methods of collagen extraction were acid hydrolysis and enzymatic hydrolysis. To determine whether the extracted collagen is a suitable substitute for animal collagen in different industries, it is required to characterize its physicochemical qualities. This study discovered a new application for marine collagen in the food industry: The sea cucumber has collagen with a greater yield in pepsin extraction with good physicochemical qualities.

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.

Protein Hydrolysates from Fishery Processing By-Products: Production, Characteristics, Food Applications, and Challenges

Fish processing by-products such as frames, trimmings, and viscera of commercial fish species are rich in proteins. Thus, they could potentially be an economical source of proteins that may be used to obtain bioactive peptides and functional protein hydrolysates for the food and nutraceutical industries. The structure, composition, and biological activities of peptides and hydrolysates depend on the freshness and the actual composition of the material. Peptides isolated from fishery by-products showed antioxidant activity. Changes in hydrolysis parameters changed the sequence and properties of the peptides and determined their physiological functions. The optimization of the value of such peptides and the production costs must be considered for each particular source of marine by-products and for their specific food applications. This review will discuss the functional properties of fishery by-products prepared using hydrolysis and their potential food applications. It also reviews the structure-activity relationships of the antioxidant activity of peptides as well as challenges to the use of fishery by-products for protein hydrolysate production.

Novel Ca-Chelating Peptides from Protein Hydrolysate of Antarctic Krill (Euphausia superba): Preparation, Characterization, and Calcium Absorption Efficiency in Caco-2 Cell Monolayer Model

Antarctic krill (Euphausia superba) is the world's largest resource of animal proteins and is thought to be a high-quality resource for future marine healthy foods and functional products. Therefore, Antarctic krill was degreased and separately hydrolyzed using flavourzyme, pepsin, papain, and alcalase. Protein hydrolysate (AKH) of Antarctic krill prepared by trypsin showed the highest Ca-chelating rate under the optimized chelating conditions: a pH of 8.0, reaction time of 50 min, temperature of 50 °C, and material/calcium ratio of 1:15. Subsequently, fourteen Ca-chelating peptides were isolated from APK by ultrafiltration and a series of chromatographic methods and identified as AK, EAR, AEA, VERG, VAS, GPK, SP, GPKG, APRGH, GVPG, LEPGP, LEKGA, FPPGR, and GEPG with molecular weights of 217.27, 374.40, 289.29, 459.50, 275.30, 300.36, 202.21, 357.41, 536.59, 328.37, 511.58, 516.60, 572.66, and 358.35 Da, respectively. Among fourteen Ca-chelating peptides, VERG presented the highest Ca-chelating ability. Ultraviolet spectrum (UV), Fourier Transform Infrared (FTIR), and scanning electron microscope (SEM) analysis indicated that the VERG-Ca chelate had a dense granular structure because the N-H, C=O and -COOH groups of VERG combined with Ca2+. Moreover, the VERG-Ca chelate is stable in gastrointestinal digestion and can significantly improve Ca transport in Caco-2 cell monolayer experiments, but phytate could significantly reduce the absorption of Ca derived from the VERG-Ca chelate. Therefore, Ca-chelating peptides from protein hydrolysate of Antarctic krill possess the potential to serve as a Ca supplement in developing healthy foods.

Characterization of the structure, antioxidant activity and hypoglycemic activity of soy (Glycine max L.) protein hydrolysates

This study aimed to hydrolyze soy isolate protein (SPI) using five enzymes (alcalase, pepsin, trypsin, papain, and bromelain) in order to obtain five enzymatic hydrolysates and to elucidate the effect of enzymes on structural and biological activities of the resulting hydrolysates. The antioxidant and hypoglycemic activities of the soy protein isolate hydrolysates (SPIEHs) were evaluated through in silico analysis, revealing that the alcalase hydrolysate exhibited the highest potential, followed by the papain and bromelain hydrolysates. Subsequently, the degree of hydrolysis (DH), molecular weight distribution (MWD), amino acid composition, structure, antioxidant activities, and hypoglycemic activity in vitro of SPIEHs were analyzed. After enzymatic treatment, the particle size, polymer dispersity index (PDI), ζ-potentials, β-sheet content and α-helix content of SPIEHs was decreased, and the maximum emission wavelength of all SPIEHs exhibited red-shifted, which all suggesting the structure of SPIEHs was unfolded. More total amino acids (TAAs), aromatic amino acids (AAAs), and hydrophobic amino acids (HAAs) were found in alcalase hydrolysate. For 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, metal ion chelating activity, α-glucosidase inhibitory activity and α-amylase inhibitory activity, alcalase hydrolysate had the lowest IC50; alcalase hydrolysate and papain hydrolysate had the lowest IC50 for hydroxyl radical scavenging activity. Physiological activity of SPIEHs was evaluated thoroughly by 5-Axe cobweb charts, and the results revealed that alcalase hydrolysate exhibited the greatest biological activities.

Restoration and preservation effects of mung bean antioxidant peptides on H2O2-induced WRL-68 cells via Keap1-Nrf2 pathway

Mung bean antioxidant peptides (MBAPs) were prepared from mung bean protein hydrolysate, and four peptide sequences including Ser-Asp-Arg-Thr-Gln-Ala-Pro-His (~953 Da), Ser-His-Pro-Gly-Asp-Phe-Thr-Pro-Val (~956 Da), Ser-Asp-Arg-Trp-Phe (~710 Da), and Leu-Asp-Arg-Gln-Leu (~644 Da) were identified. The effects of MBAPs on the oxidation-induced normal human liver cell line WRL-68 were analyzed to determine the mechanism protecting the oxidation-induced injury. The results showed that the cells were subjected to certain oxidative damage by H2O2 induction, as evidenced by decreased cell number and viability, overproduction of intracellular ROS, and decreased mitochondrial membrane potential. Compared with the H2O2-induced group, the MBAP-treated oxidation-induced group exhibited significantly higher cell number and viability, and the intracellular ROS was similar to that of the control group, suggesting that MBAP scavenges excessive intracellular free radicals after acting on the oxidation-induced cells. Combined with Western blotting results, it was concluded that the MBAP-treated oxidation-induced group also significantly promoted the expression of proteins related to the kelch-like ech-related protein 1 (Keap1)/ nuclear factor e2-related factor 2 (Nrf2) signaling pathway, which resulted in an approximately 2-fold increase in antioxidant enzymes, and a decrease in malondialdehyde content of approximately 55% compared to oxidatively-induced cells, leading to the recovery of both cell morphology and viability. These results suggest that MBAPs scavenge intracellular free radicals and improve oxidative stress in hepatocytes through the expression of Keap1/Nrf2 pathway-related protein, thereby reducing oxidative attack on the liver. Therefore, MBAP is applied as a nutritional ingredient in the functional food field, and this study provides a theoretical basis for the high utilization of mung bean proteins.

Angiotensin-I-Converting Enzyme (ACE)-Inhibitory Peptides from the Collagens of Monkfish (Lophius litulon) Swim Bladders: Isolation, Characterization, Molecular Docking Analysis and Activity Evaluation

The objective of this study was to isolate and characterize collagen and angiotensin-I-converting enzyme (ACE)-inhibitory (ACEi) peptides from the swim bladders of monkfish (Lophius litulon). Therefore, acid-soluble collagen (ASC-M) and pepsin-soluble collagen (PSC-M) with yields of 4.27 ± 0.22% and 9.54 ± 0.51%, respectively, were extracted from monkfish swim bladders using acid and enzyme methods. The ASC-M and PSC-M contained Gly (325.2 and 314.9 residues/1000 residues, respectively) as the major amino acid, but they had low imino acid content (192.5 and 188.6 residues/1000 residues, respectively) in comparison with collagen from calf skins (CSC) (216.6 residues/1000 residues). The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns and ultraviolet (UV) absorption spectrums of ASC-M and PSC-M illustrated that they were mainly composed of type I collagen. Subsequently, three ACEi peptides were isolated from a PSC-M hydrolysate prepared via a double-enzyme system (alcalase + neutrase) and identified as SEGPK (MHP6), FDGPY (MHP7) and SPGPW (MHP9), with molecular weights of 516.5, 597.6 and 542.6 Da, respectively. SEGPK, FDGPY and SPGPW displayed remarkable anti-ACE activity, with IC50 values of 0.63, 0.94 and 0.71 mg/mL, respectively. Additionally, a molecular docking assay demonstrated that the affinities of SEGPK, FDGPY and SPGPW with ACE were -7.3, -10.9 and -9.4 kcal/mol, respectively. The remarkable ACEi activity of SEGPK, FDGPY and SPGPW was due to their connection with the active pockets and/or sites of ACE via hydrogen bonding, hydrophobic interaction and electrostatic force. Moreover, SEGPK, FDGPY and SPGPW could protect HUVECs by controlling levels of nitric oxide (NO) and endothelin-1 (ET-1). Therefore, this work provides an effective means for the preparation of collagens and novel ACEi peptides from monkfish swim bladders, and the prepared ACEi peptides, including SEGPK, FDGPY and SPGPW, could serve as natural functional components in the development of health care products to control hypertension.

Trash to Treasure: An Up-to-Date Understanding of the Valorization of Seafood By-Products, Targeting the Major Bioactive Compounds

Fishery production is exponentially growing, and its by-products negatively impact industries' economic and environmental status. The large amount of bioactive micro- and macromolecules in fishery by-products, including lipids, proteins, peptides, amino acids, vitamins, carotenoids, enzymes, collagen, gelatin, chitin, chitosan, and fucoidan, need to be utilized through effective strategies and proper management. Due to the bioactive and healthy compounds in fishery discards, these components can be used as functional food ingredients. Fishery discards have inorganic or organic value to add to or implement in various sectors (such as the agriculture, medical, and pharmaceutical industries). However, the best use of these postharvest raw materials for human welfare remains unelucidated in the scientific community. This review article describes the most useful techniques and methods, such as obtaining proteins and peptides, fatty acids, enzymes, minerals, and carotenoids, as well as collagen, gelatin, and polysaccharides such as chitin-chitosan and fucoidan, to ensure the best use of fishery discards. Marine-derived bioactive compounds have biological activities, such as antioxidant, anticancer, antidiabetic, anti-inflammatory, and antimicrobial activities. These high-value compounds are used in various industrial sectors, such as the food and cosmetic industries, owing to their unique functional and characteristic structures. This study aimed to determine the gap between misused fishery discards and their effects on the environment and create awareness for the complete valorization of fishery discards, targeting a sustainable world.

Production, identification, in silico analysis, and cytoprotection on H2O2-induced HUVECs of novel angiotensin-I-converting enzyme inhibitory peptides from Skipjack tuna roes

Background

Exceeding 50% tuna catches are regarded as byproducts in the production of cans. Given the high amount of tuna byproducts and their environmental effects induced by disposal and elimination, the valorization of nutritional ingredients from these by-products receives increasing attention.

Objective

This study was to identify the angiotensin-I-converting enzyme (ACE) inhibitory (ACEi) peptides from roe hydrolysate of Skipjack tuna (Katsuwonus pelamis) and evaluate their protection functions on H₂O₂-induced human umbilical vein endothelial cells (HUVECs).

Methods

Protein hydrolysate of tuna roes with high ACEi activity was prepared using flavourzyme, and ACEi peptides were isolated from the roe hydrolysate using ultrafiltration and chromatography methods and identified by ESI/MS and Procise Protein/Peptide Sequencer for the N-terminal amino acid sequence. The activity and mechanism of action of isolated ACEi peptides were investigated through molecular docking and cellular experiments.

Results

Four ACEi peptides were identified as WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12), respectively. The affinity of WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) with ACE was -8.590, -9.703, -9.325, and -8.036 kcal/mol, respectively. The molecular docking experiment elucidated that the significant ACEi ability of WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) was mostly owed to their tight bond with ACE's active sites/pockets via hydrophobic interaction, electrostatic force and hydrogen bonding. Additionally, WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) could dramatically elevate the Nitric Oxide (NO) production and bring down endothelin-1 (ET-1) secretion in HUVECs, but also abolish the opposite impact of norepinephrine (0.5 μM) on the production of NO and ET-1. Moreover, WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) could lower the oxidative damage and apoptosis rate of H₂O₂-induced HUVECs, and the mechanism indicated that they could increase the content of NO and activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to decrease the generation of reactive oxygen species (ROS) and malondialdehyde (MDA).

Conclusion

WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) are beneficial ingredients for healthy products ameliorating hypertension and cardiovascular diseases.

Antioxidant Peptides from Monkfish Swim Bladders: Ameliorating NAFLD In Vitro by Suppressing Lipid Accumulation and Oxidative Stress via Regulating AMPK/Nrf2 Pathway

In this study, we investigate the ameliorating functions of QDYD (MSP2), ARW (MSP8), DDGGK (MSP10), YPAGP (MSP13) and DPAGP (MSP18) from monkfish swim bladders on an FFA-induced NAFLD model of HepG2 cells. The lipid-lowering mechanisms revealed that these five oligopeptides can up-regulate the expression of phospho-AMP-activated protein kinase (p-AMPK) proteins to inhibit the expression of the sterol regulatory element binding protein-1c (SREBP-1c) proteins on increasing lipid synthesis and up-regulating the expression of the PPAP-α and CPT-1 proteins on promoting the β-oxidation of fatty acids. Moreover, QDYD (MSP2), ARW (MSP8), DDGGK (MSP10), YPAGP (MSP13) and DPAGP (MSP18) can significantly inhibit reactive oxygen species' (ROS) production, promote the activities of intracellular antioxidases (superoxide dismutase, SOD; glutathione peroxidase, GSH-PX; and catalase, CAT) and bring down the content of malondialdehyde (MDA) derived from lipid peroxidation. Further investigations revealed that the regulation of these five oligopeptides on oxidative stress was achieved through activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway to raise the expression levels of the heme oxygenase 1 (HO-1) protein and downstream antioxidant proteases. Therefore, QDYD (MSP2), ARW (MSP8), DDGGK (MSP10), YPAGP (MSP13) and DPAGP (MSP18) could serve as candidate ingredients to develop functional products for treating NAFLD.

Structural Identification and Antioxidant Activity of Loach Protein Enzymatic Hydrolysates

Loach, rich in nutrients, such as proteins, amino acids, and mineral elements, is being gradually favored by consumers. Therefore, in this study, the antioxidant activity and structural characteristics of loach peptides were comprehensively analyzed. The loach protein (LAP) with a molecular weight between 150 and 3000 Da was graded by ultrafiltration and nanofiltration processes, which exhibited excellent scavenging activity against DPPH radical (IC50 2.91 ± 0.02 mg/mL), hydroxyl radical (IC50 9.95 ± 0.03 mg/mL), and superoxide anion radical (IC50 13.67 ± 0.33 mg/mL). Additionally, LAP was purified by gel filtration chromatography, and two principal components (named as LAP-I and LAP-II) were isolated. A total of 582 and 672 peptides were identified in LAP-I and LAP-II, respectively, through structural analysis. The XRD results revealed that LAP-I and LAP-II had an irregular amorphous structure. The 2D-NMR spectroscopy results suggested that LAP-I had a compact stretch conformation in the D₂O solution, while LAP-II had a folded conformation. Overall, the study results suggested that loach peptide could be a potential antioxidant agent and might provide valuable information for chain conformation and antioxidant mechanism research further.

Improving the Sustainability of Processing By-Products: Extraction and Recent Biological Activities of Collagen Peptides

Society and consumers are increasingly concerned about food safety and the sustainability of food production systems. A significant amount of by-products and discards are generated during the processing of aquatic animals, which still needs to be fully utilized by the food industry. The management and sustainable use of these resources are essential to avoiding environmental pollution and resource waste. These by-products are rich in biologically active proteins, which can be converted into peptides by enzymatic hydrolysis or fermentation treatment. Therefore, exploring the extraction of collagen peptides from these by-products using an enzymatic hydrolysis technology has attracted a wide range of attention from numerous researchers. Collagen peptides have been found to possess multiple biological activities, including antioxidant, anticancer, antitumor, hypotensive, hypoglycemic, and anti-inflammatory properties. These properties can enhance the physiological functions of organisms and make collagen peptides useful as ingredients in food, pharmaceuticals, or cosmetics. This paper reviews the general methods for extracting collagen peptides from various processing by-products of aquatic animals, including fish skin, scales, bones, and offal. It also summarizes the functional activities of collagen peptides as well as their applications.

Marine Bioactive Peptides-Structure, Function and Application

Marine organisms live in harsh marine habitats, causing them to have significantly different and more diverse proteins than those of terrestrial organisms [...].

Eighteen Novel Bioactive Peptides from Monkfish (Lophius litulon) Swim Bladders: Production, Identification, Antioxidant Activity, and Stability

In the study, papain was chosen from five proteases to hydrolyze proteins of monkfish swim bladders for effectively utilizing monkfish (Lophius litulon) processing byproducts, and the hydrolysis conditions of papain were optimized as hydrolysis temperature of 65 °C, pH 7.5, enzyme dose 2.5% and time 5 h using single-factor and orthogonal experiments. Eighteen peptides were purified from the swim bladder hydrolysate of monkfish by ultrafiltration and gel permeation chromatography methods and identified as YDYD, QDYD, AGPAS, GPGPHGPSGP, GPK, HRE, GRW, ARW, GPTE, DDGGK, IGPAS, AKPAT, YPAGP, DPT, FPGPT, GPGPT, GPT and DPAGP, respectively. Among eighteen peptides, GRW and ARW showed significant DPPH· scavenging activities with EC₅₀ values of 1.053 ± 0.003 and 0.773 ± 0.003 mg/mL, respectively; YDYD, QDYD, GRW, ARW and YPAGP revealed significantly HO· scavenging activities with EC₅₀ values of 0.150 ± 0.060, 0.177 ± 0.035, 0.201 ± 0.013, 0.183 ± 0.0016 and 0.190 ± 0.010 mg/mL, respectively; YDYD, QDYD, ARW, DDGGK and YPAGP have significantly O2-· scavenging capability with EC₅₀ values of 0.126 ± 0.0005, 0.112 ± 0.0028, 0.127 ± 0.0002, 0.128 ± 0.0018 and 0.107 ± 0.0002 mg/mL, respectively; and YDYD, QDYD and YPAGP showed strong ABTS⁺· scavenging ability with EC₅₀ values of 3.197 ± 0.036, 2.337 ± 0.016 and 3.839 ± 0.102 mg/mL, respectively. YDYD, ARW and DDGGK displayed the remarkable ability of lipid peroxidation inhibition and Ferric-reducing antioxidant properties. Moreover, YDYD and ARW can protect Plasmid DNA and HepG2 cells against H₂O₂-induced oxidative stress. Furthermore, eighteen isolated peptides had high stability under temperatures ranging from 25-100 °C; YDYD, QDYD, GRW and ARW were more sensitive to alkali treatment, but DDGGK and YPAGP were more sensitive to acid treatment; and YDYD showed strong stability treated with simulated GI digestion. Therefore, the prepared antioxidant peptides, especially YDYD, QDYD, GRW, ARW, DDGGK and YPAGP from monkfish swim bladders could serve as functional components applied in health-promoting products because of their high-antioxidant functions.

Preparation of Cod Skin Collagen Peptides/Chitosan-Based Temperature-Sensitive Gel and Its Anti-Photoaging Effect in Skin

Background

Photoaging decreases quality of life and increases the risk of skin cancer, underscoring the urgent need to explore natural, high-efficacy, anti-skin photoaging (SP) active substances.

Methods

In this study, a gel (CS/CSCPs/β-GP gel) was prepared using chitosan (CS) and sodium β-glycerophosphate (β-GP) through crosslinking with small molecular CSCPs as the carried drug. We evaluated its structural characteristics and properties. The effect of CS/CSCPs/β-GP gel on the degree of ultraviolet (UV)-induced skin aging of mice was investigated through comparative analysis of skin damage, the integrity of collagen tissues and elastic fibers, levels of reactive oxygen species (ROS) and key inflammatory factors (tumor necrosis factor [TNF]-α and interleukin [IL]-1β, IL-6, and IL-10), and tissue expression of matrix metalloproteinase-3 (MMP-3) after repeated UV irradiation in a nude mice SP model.

Results

The results showed that CS/CSCPs/β-GP gel was successfully prepared and had the desired characteristics. Compared with CSCPs alone, the CS/CSCPs/β-GP gel more evidently improved typical photoaging characteristics on mouse dorsal skin. It also increased the moisture content, causing the skin to become glossy and elastic. Pathological skin analysis revealed that this peptide-carrying gel can effectively inhibit epidermal thickening, reduce tissue inflammatory infiltration, suppress collagen fiber degradation, increase the collagen content, alleviate structural elastic fiber damage, and significantly inhibit abnormal MMP-3 expression. In addition, biochemical analysis showed that the CS/CSCPs/β-GP gel can effectively inhibit the elevated expressions of ROS and key proinflammatory factors (TNF-α, IL-1β, IL-6) in photoaging skin tissues and promote expression of the anti-inflammatory factor IL-10.

Conclusion

SP can cause many clinical skin diseases, such as solar freckle-like nevus, solar keratosis, cutaneous melanoma, and squamous cell carcinoma. CSCPs are a high-efficacy anti-SP natural active substance and CS/CSCPs/β-GP gel can synergistically enhance the CSCPs' anti-SP effect. The mechanism is likely related to the inhibited activation of ROS/nuclear transcription factor-κB signaling and the expression of downstream inflammatory factors.

Bioactive Peptides from Skipjack Tuna Cardiac Arterial Bulbs (II): Protective Function on UVB-Irradiated HaCaT Cells through Antioxidant and Anti-Apoptotic Mechanisms

The aim of this study was to investigate the protective function and mechanism of TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) from skipjack tuna cardiac arterial bulbs on skin photoaging using UVB-irradiated HaCaT cell model. The present results indicated that TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) had significant cytoprotective effect on UVB-irradiated HaCaT cells (p < 0.001). Hoechst 33342 staining showed that apoptosis of UV-irradiated HaCaT cells could be significantly reduced by the treatment of TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM); JC-1 staining showed that TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) could protect HaCaT cells from apoptosis by restoring mitochondrial membrane potential (MMP); Furthermore, TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) could significantly down-regulate the ratio of Bax/Bcl-2 and reduce the expression level of the apoptosis-executing protein Caspase-3 by decreasing the expression of protein Caspase-8 and Caspase-9 (p < 0.05). The action mechanism indicated that TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) could up-regulate the expression levels of Nrf2, NQO1 and HO-1 (p < 0.05), which further increased the activity of downstream proteases (SOD, CAT and GSH-Px), and scavenged reactive oxygen species (ROS) and decreased the intracellular levels of malondialdehyde (MDA). In addition, molecular docking indicated that TCP3 (PKK) and TCP6 (YEGGD) could competitively inhibit the Nrf2 binding site because they can occupy the connection site of Nrf2 by binding to the Kelch domain of Keap1 protein. TCP9 (GPGLM) was inferred to be non-competitive inhibition because it could not bind to the active site of the Kelch domain of Keap1 protein. In summary, the antioxidant peptides TCP3 (PKK), TCP6 (YEGGD) and TCP9 (GPGLM) from cardiac arterial bulbs of skipjack tuna can effectively protect HaCaT cells from UVB-irradiated damage and can be used in the development of healthy and cosmetic products to treat diseases caused by UV radiation.

Gelatin and Chitosan as Meat By-Products and Their Recent Applications

Meat by-products such as bones, skin, horns, hooves, feet, skull, etc., are produced from slaughtered mammals. Innovative solutions are very important to achieving sustainability and obtaining the added value of meat by-products with the least impact on the environment. Gelatin, which is obtained from products high in collagen, such as dried skin and bones, is used in food processing, and pharmaceuticals. Chitosan is derived from chitin and is well recognized as an edible polymer. It is a natural product that is non-toxic and environmentally friendly. Recently, chitosan has attracted researchers' interests due to its biological activities, including antimicrobial, antitumor, and antioxidant properties. In this review, article, we highlighted the recent available information on the application of gelatin and chitosan as antioxidants, antimicrobials, food edible coating, enzyme immobilization, biologically active compound encapsulation, water treatment, and cancer diagnosis.