Isolation and characterization of collagen and antioxidant collagen peptides from scales of croceine croaker (Pseudosciaena crocea)

Purification, characterization and application of collagenolytic protease from Bacillus subtilis strain MPK

A new extracellular protease from Bacillus subtilis strain MPK with collagenolytic activity was isolated and purified. Fish skin which otherwise would be treated as waste is used as substrate for the production of protease. Using various techniques such as ammonium sulphate precipitation and ion exchange chromatography, protease was purified and characterized subsequently. Protease of approximately 61 kDa molecular weight was purified by 135.7-fold with 18.42% enzyme recovery. The protease showed effective properties like pH and temperature stability over a broad range with optimum pH 7.5 and temperature 60 °C. Km and Vmax were found to be 1.92 mg ml-1 and 1.02 × 10-4 mol L-1 min-1, respectively. The protease exhibited stability in various ions, surfactants, inhibitors and organic solvents. Subsequently, the protease was successfully utilized for collagen hydrolysis to generate collagen peptides; thus, the produced protease would be a potential candidate for multifaceted applications in food and pharmaceutical industries due to its significant characteristics and collagenolytic properties.

Antioxidant peptides, the guardian of life from oxidative stress

Reactive oxygen species (ROS) are produced during oxidative metabolism in aerobic organisms. Under normal conditions, ROS production and elimination are in a relatively balanced state. However, under internal or external environmental stress, such as high glucose levels or UV radiation, ROS production can increase significantly, leading to oxidative stress. Excess ROS production not only damages biomolecules but is also closely associated with the pathogenesis of many diseases, such as skin photoaging, diabetes, and cancer. Antioxidant peptides (AOPs) are naturally occurring or artificially designed peptides that can reduce the levels of ROS and other pro-oxidants, thus showing great potential in the treatment of oxidative stress-related diseases. In this review, we discussed ROS production and its role in inducing oxidative stress-related diseases in humans. Additionally, we discussed the sources, mechanism of action, and evaluation methods of AOPs and provided directions for future studies on AOPs.

Marine collagen: Unveiling the blue resource-extraction techniques and multifaceted applications

Marine organisms such as fish and shellfish are composed of compounds with properties and characteristics that have been proven useful in a variety of sectors such as cosmetics, healthcare (wound healing), food industries, and tissue engineering. Collagen extraction from fish waste as a "blue resource" has attracted research attention over the past decade. Around 75 % of fish waste contains a high concentration of collagen. This has driven research in the conversion of these low-cost by-products into valuable products. Collagen extracted by acidic or/and enzymatic methods is gaining a lot of attention today due to its low cost and high yield. Fermentation and enzymatic hydrolysis stand out as one of the most environmentally sustainable and ecologically friendly methods for collagen extraction. Because of its great biocompatibility, excellent bioactivity, and low antigenicity, marine collagen is receiving more attention. Furthermore, collagen-derived peptides may exhibit interesting antioxidant activity, potent antihypertensive activity, and antimicrobial activity against different strains of bacteria. This review focuses on the advancements in extraction and detection methods of marine collagen, both from a technological and legislative standpoint, in addition to exploring its diverse range of application domains.

Isolation, Identification, and Biological Activity Analysis of Swim Bladder Polypeptides from Acipenser schrencki

Swim bladder polypeptides (SBPs) of Acipenser schrencki were analyzed for their antioxidant activity and physicochemical properties. The results showed the optimal enzymatic conditions were alkaline protease with a solid-to-liquid ratio of 1:20, an incubation time of 4 h, a temperature of 55 °C, and an enzyme dosage of 5000 U/g. Three different molecular weight fractions (F1, F2, and F3) were obtained via ultrafiltration. F3 (912.44-2135.82 Da) showed 77.90%, 72.15%, and 66.25% removal of O₂•^-, DPPH•, and •OH, respectively, at 10 mg/mL, which was significantly higher than the F1 and F2 fractions (p < 0.05). F3 contained proline (6.17%), hydroxyproline (5.28%), and hydrophobic amino acids (51.39%). The UV spectrum of F3 showed maximum absorption at 224 nm. Peptide sequence analysis showed that F3 contained antioxidant peptides (MFGF, GPPGPRGPPGL, and GPGPSGERGPPGPM) and exhibited inhibitory activities on angiotensin-converting enzyme and dipeptidyl peptidase III/IV (FRF, FPFL and LPGLF). F3 was considered a good raw material for obtaining bioactive peptides.

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.

Chitosan-based hemostatic sponges as new generation hemostatic materials for uncontrolled bleeding emergency: Modification, composition, and applications

The choice of hemostatic technique is a curial concern for surgery and as first-aid treatment in combat. To treat uncontrolled bleeding in complex wound environments, chitosan-based hemostatic sponges have attracted significant attention in recent years because of the excellent biocompatibility, degradability, hemostasis and antibacterial properties of chitosan and their unique sponge-like morphology for high fluid absorption rate and priority aggregation of blood cells/platelets to achieve rapid hemostasis. In this review, we provide a historical perspective on the use of chitosan hemostatic sponges as the new generation of hemostatic materials for uncontrolled bleeding emergencies in complex wounds. We summarize the modification of chitosan, review the current status of preparation protocols of chitosan sponges based on various composite systems, and highlight the recent achievements on the detailed breakdown of the existing chitosan sponges to present the relationship between their composition, physical properties, and hemostatic capacity. Finally, the future opportunities and challenges of chitosan hemostatic sponges are also proposed.

Characteristics and Properties of Acid- and Pepsin-Solubilized Collagens from the Tail Tendon of Skipjack Tuna (Katsuwonus pelamis)

The tail tendons of skipjack tuna (Katsuwonus pelamis), a by-product from the meat-separation process in canned-tuna production, was used as an alternative source of collagen extraction. The acid-solubilized collagens using vinegar (VTC) and acetic-acid (ATC) extraction and pepsin-solubilized collagen (APTC) were extracted from tuna-tail tendon. The physiochemical properties and characteristics of those collagens were investigated. The obtained yield of VTC, ATC, and APTC were 7.88 ± 0.41, 8.67 ± 0.35, and 12.04 ± 0.07%, respectively. The determination of protein-collagen solubility, the effect of pH and NaCl on collagen solubility, Fourier-transform infrared spectroscopy (FTIR) spectrum, and microstructure of the collagen-fibril surface using a scanning electron microscope (SEM) were done. The protein solubility of VTC, ATC, and APTC were 0.44 ± 0.03, 0.52 ± 0.07, and 0.67 ± 0.12 mg protein/mg collagen. The solubility of collagen decreased with increasing of NaCl content. These three collagens were good solubility at low pH with the highest solubility at pH 5. The FTIR spectrum showed absorbance of Amide A, Amide B, Amide I, Amide II, and Amide III groups as 3286-3293 cm^-1, 2853-2922 cm^-1, 1634-1646 cm^-1, 1543-1544 cm^-1, and 1236-1237 cm^-1, respectively. The SEM analysis indicated a microstructure of collagen surface as folding of fibril with small pore.

Potential Cosmetic Active Ingredients Derived from Marine By-Products

The market demand for marine-based cosmetics has shown a tremendous growth rate in the last decade. Marine resources represent a promising source of novel bioactive compounds for new cosmetic ingredient development. However, concern about sustainability also becomes an issue that should be considered in developing cosmetic ingredients. The fisheries industry (e.g., fishing, farming, and processing) generates large amounts of leftovers containing valuable substances, which are potent sources of cosmeceutical ingredients. Several bioactive substances could be extracted from the marine by-product that can be utilized as a potent ingredient to develop cosmetics products. Those bioactive substances (e.g., collagen from fish waste and chitin from crustacean waste) could be utilized as anti-photoaging, anti-wrinkle, skin barrier, and hair care products. From this perspective, this review aims to approach the potential active ingredients derived from marine by-products for cosmetics and discuss the possible activity of those active ingredients in promoting human beauty. In addition, this review also covers the prospect and challenge of using marine by-products toward the emerging concept of sustainable blue cosmetics.

Biophysical and in vitro wound healing assessment of collagen peptides processed from fish skin waste

The present study was conducted to examine the bioactive and wound healing properties of collagen hydrolysate derived from Piaractus brachypomus (pacu) fish skin waste. Collagen type I (P coll.) yielding 72.25% was isolated from skin waste by following acid-soluble collagen extraction method. Further, collagen was fragmented using bacterial collagenase and the processed collagen hydrolysate (peptides) was in the range of 10–15 kDa that was further purified using ion-exchange chromatography. The FTIR spectra of both P coll. and collagen hydrolysate (PSCH) were nearly similar showing that PSCH retained the structural and chemical composition similar to its parent molecule (P coll.). Solubility analysis revealed that PSCH has slightly better solubility compared to P coll. Similarly, scanning electron micrographs also exhibited more uniform and porous microstructure of PSCH compared to P coll. Further, PSCH was found to be efficient in peroxide quenching (64.5%) and radical scavenging activities (85.74%). MTT studies confirmed PSCH to be non-toxic displaying 84.68% cell viability at the highest concentration (3 mg/ml) and hemocompatibility test revealed PSCH to be non-hemolytic with minimal lysis of only 2.1% of human RBCs. In addition, PSCH also displayed a remarkable wound closure ability of more than 80% at 12 h and 100% within 24 h. Hence, these findings suggest that recycled PSCH has potent wound healing ability and can be produced economically on a large scale for possible biological applications in regenerative medicine.

Bioactive Peptides from Skipjack Tuna Cardiac Arterial Bulbs: Preparation, Identification, Antioxidant Activity, and Stability against Thermal, pH, and Simulated Gastrointestinal Digestion Treatments

Cardiac arterial bulbs of Skipjack tuna (Katsuwonus pelamis) are rich in elastin, and its hydrolysates are high quality raw materials for daily cosmetics. In order to effectively utilizing Skipjack tuna processing byproducts-cardiac arterial bulbs and to prepare peptides with high antioxidant activity, pepsin was selected from six proteases for hydrolyzing proteins, and the best hydrolysis conditions of pepsin were optimized. Using ultrafiltration and chromatographic methods, eleven antioxidant peptides were purified from protein hydrolysate of tuna cardiac arterial bulbs. Four tripeptides (QGD, PKK, GPQ and GLN) were identified as well as seven pentapeptides (GEQSN, GEEGD, YEGGD, GEGER, GEGQR, GPGLM and GDRGD). Three out of them, namely the tripeptide PKK and the pentapeptides YEGGD and GPGLM exhibited the highest radical scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and superoxide anion assays. They also showed to protect plasmid DNA and HepG2 cells against H₂O₂-induced oxidative stress. Furthermore, they exhibited high stability under temperature ranged from 20-100 °C, pH values ranged from 3-11, and they simulated gastrointestinal digestion for 240 min. These results suggest that the prepared eleven antioxidant peptides from cardiac arterial bulbs, especially the three peptides PKK, YEGGD, and GPGLM, could serve as promising candidates in health-promoting products due to their high antioxidant activity and their stability.

In Vitro Antioxidant and Antiaging Activities of Collagen and Its Hydrolysate from Mackerel Scad Skin (Decapterus macarellus)

The skin of mackerel scad fish (Decapterus macarellus) is a new source for pepsin-soluble collagen and its hydrolysate, both of which have never been explored. This study aims to characterize and determine the in vitro antioxidant, antiglycation, and antityrosinase activity of pepsin-soluble collagen (PSC) and hydrolyzed collagen (HC) from mackerel scad skin. PSC was extracted using 0.5 M acetic acid containing 0.1% pepsin for 48 h at 4 °C. The obtained PSC was then hydrolyzed with collagenase type II (6250 U/g) to produce HC. The PSC yield obtained was 6.39 ± 0.97%, with a pH of 6.76 ± 0.18, while the HC yield was 96% from PSC. SDS-PAGE and Fourier Transform Infrared (FTIR) analysis showed the typical features of type I collagen. HC demonstrated high solubility (66.75–100%) throughout the entire pH range (1–10). The PSC and HC from mackerel scad skin showed antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH), with IC50 values of 148.55 ± 3.14 ppm and 34.966 ± 0.518 ppm, respectively. In the antiglycation test, PSC had an IC50 value of 239.29 ± 15.67 ppm, while HC had an IC50 of 68.43 ± 0.44 ppm. PSC also exhibited antityrosinase activity, with IC50 values of 234.66 ± 0.185 ppm (on the L-DOPA substrate), while HC had an IC50 value of 79.35 ± 0.5 ppm. Taken together, these results suggest that the skin of mackerel scad fish has potential antiaging properties and can be further developed for pharmaceutical and cosmetic purposes.

Novel angiotensin-converting enzyme inhibitory peptides from tuna byproducts—milts: Preparation, characterization, molecular docking study, and antioxidant function on H2O2-damaged human umbilical vein endothelial cells

To prepare peptides with high angiotensin-converting enzyme (ACE) inhibitory (ACEi) activity, Alcalase was screened from five proteases and employed to prepare protein hydrolysate (TMH) of skipjack tuna (Katsuwonus pelamis) milts. Subsequently, 10 novel ACEi peptides were isolated from the high-ACEi activity TMH and identified as Tyr-Asp-Asp (YDD), Thr-Arg-Glu (TRE), Arg-Asp-Tyr (RDY), Thr-Glu-Arg-Met (TERM), Asp-Arg-Arg-Tyr-Gly (DRRYG), Ile-Cys-Tyr (ICY), Leu-Ser-Phe-Arg (LSFR), Gly-Val-Arg-Phe (GVRF), Lys-Leu-Tyr-Ala-Leu-Phe (KLYALF), and Ile-Tyr-Ser-Pro (IYSP) with molecular weights of 411.35, 404.41, 452.45, 535.60, 665.69, 397.48, 521.61, 477.55, 753.91, and 478.53 Da, respectively. Among them, the IC₅₀ values of ICY, LSFR, and IYSP on ACE were 0.48, 0.59, and 0.76 mg/mL, respectively. The significant ACEi activity of ICY, LSFR, and IYSP with affinities of −7.0, −8.5, and −8.3 kcal/mol mainly attributed to effectively combining with the ACEi active sites through hydrogen bonding, electrostatic force, and hydrophobic interaction. Moreover, ICY, LSFR, and IYSP could positively influence the production of nitric oxide (NO) and endothelin-1 (ET-1) secretion in human umbilical vein endothelial cells (HUVECs) and weaken the adverse impact of norepinephrine (NE) on the production of NO and ET-1. In addition, ICY, LSFR, and IYSP could provide significant protection to HUVECs against H₂O₂ damage by increasing antioxidase levels to decrease the contents of reactive oxide species and malondialdehyde. Therefore, the ACEi peptides of ICY, LSFR, and IYSP are beneficial functional molecules for healthy foods against hypertension and cardiovascular diseases.

Collagen Membrane Derived from Fish Scales for Application in Bone Tissue Engineering

Guided tissue/bone regeneration (GTR/GBR) is currently the main treatment for alveolar bone regeneration. The commonly used barrier membranes in GTR/GBR are collagen membranes from mammals such as porcine or cattle. Fish collagen is being explored as a potential substitute for mammalian collagen due to its low cost, no zoonotic risk, and lack of religious constraints. Fish scale is a multi-layer natural collagen composite with high mechanical strength, but its biomedical application is limited due to the low denaturation temperature of fish collagen. In this study, a fish scale collagen membrane with a high denaturation temperature of 79.5 °C was prepared using an improved method based on preserving the basic shape of fish scales. The fish scale collagen membrane was mainly composed of type I collagen and hydroxyapatite, in which the weight ratios of water, organic matter, and inorganic matter were 20.7%, 56.9%, and 22.4%, respectively. Compared to the Bio-Gide^® membrane (BG) commonly used in the GTR/GBR, fish scale collagen membrane showed good cytocompatibility and could promote late osteogenic differentiation of cells. In conclusion, the collagen membrane prepared from fish scales had good thermal stability, cytocompatibility, and osteogenic activity, which showed potential for bone tissue engineering applications.

Suitability of Marine- and Porcine-Derived Collagen Type I Hydrogels for Bioprinting and Tissue Engineering Scaffolds

Collagens from a wide array of animals have been explored for use in tissue engineering in an effort to replicate the native extracellular environment of the body. Marine-derived biomaterials offer promise over their conventional mammalian counterparts due to lower risk of disease transfer as well as being compatible with more religious and ethical groups within society. Here, collagen type I derived from a marine source (Macruronus novaezelandiae, Blue Grenadier) is compared with the more established porcine collagen type I and its potential in tissue engineering examined. Both collagens were methacrylated, to allow for UV crosslinking during extrusion 3D printing. The materials were shown to be highly cytocompatible with L929 fibroblasts. The mechanical properties of the marine-derived collagen were generally lower than those of the porcine-derived collagen; however, the Young’s modulus for both collagens was shown to be tunable over a wide range. The marine-derived collagen was seen to be a potential biomaterial in tissue engineering; however, this may be limited due to its lower thermal stability at which point it degrades to gelatin.

Extraction and Identification of Three New Urechis unicinctus Visceral Peptides and Their Antioxidant Activity

The viscera of Urechis unicinctus with polypeptides, fatty acids, and amino acids are usually discarded during processing to food. In order to improve the utilization value of the viscera of Urechis unicinctus and avoid resource waste, antioxidant polypeptides were isolated from the viscera of Urechis unicinctus. First, a protein hydrolysate of Urechis unicinctus (UUPH) was prepared by ultrasonic-assisted enzymatic hydrolysis, and the degree of hydrolysis was as high as 79.32%. Subsequently, three new antioxidant peptides (P1, P2, and P3) were purified from UUPH using ultrafiltration and chromatography, and their amino acid sequences were identified as VTSALVGPR, IGLGDEGLRR, TKIRNEISDLNER, respectively. Then, the antioxidant activity of the polypeptide was predicted by the structure-activity relationship and finally verified by experiments on eukaryotic cells. The P1 peptide exhibited the strongest antioxidant activity among these three antioxidant peptides. Furthermore, P1, P2, and P3 have no toxic effect on RAW264.7 cells at the concentration of 0.01~2 mg/mL and can protect RAW264.7 cells from H2O2-induced oxidative damage in a concentration-dependent manner. These results suggested that these three new antioxidant peptides were isolated from the viscera of Urechis unicinctus, especially the P1 peptide, which might serve as potential antioxidants applied in health-derived food or beverages. This study further developed a new use of the by-product of Urechis unicinctus, which improved the comprehensive utilization of marine biological resources.

Preparation, Characterization, and Cytoprotective Effects on HUVECs of Fourteen Novel Angiotensin-I-Converting Enzyme Inhibitory Peptides From Protein Hydrolysate of Tuna Processing By-Products

To effectively utilize skipjack tuna (Katsuwonus pelamis) processing by-products to prepare peptides with high angiotensin-I-converting enzyme (ACE) inhibitory (ACEi) activity, Neutrase was selected from five kinds of protease for hydrolyzing skipjack tuna dark muscle, and its best hydrolysis conditions were optimized as enzyme dose of 1.6%, pH 6.7, and temperature of 50°C using single factor and response surface experiments. Subsequently, 14 novel ACEi peptides were prepared from the high ACEi protein hydrolysate and identified as TE, AG, MWN, MEKS, VK, MQR, MKKS, VKRT, IPK, YNY, LPRS, FEK, IRR, and WERGE. MWN, MEKS, MKKS, and LPRS displayed significantly ACEi activity with IC₅₀ values of 0.328 ± 0.035, 0.527 ± 0.030, 0.269 ± 0.006, and 0.495 ± 0.024 mg/mL, respectively. Furthermore, LPRS showed the highest increasing ability on nitric oxide (NO) production among four ACEi peptides combining the direct increase and reversing the negative influence of norepinephrine (NE), and MKKS showed the highest ability on directly decreasing and reversing the side effects of NE on the secretion level of endothelin-1 (ET-1) among four ACEi peptides. These findings demonstrate that seafood by-product proteins are potential ACEi peptide sources and prepared ACEi peptides from skipjack tuna dark muscle, which are beneficial components for functional food against hypertension and cardiovascular diseases.

Fish Collagen Peptides Protect against Cisplatin-Induced Cytotoxicity and Oxidative Injury by Inhibiting MAPK Signaling Pathways in Mouse Thymic Epithelial Cells

Thymic epithelial cells (TECs) account for the most abundant and dominant stromal component of the thymus, where T cells mature. Oxidative- or cytotoxic-stress associated injury in TECs, a significant and common problem in many clinical settings, may cause a compromised thymopoietic capacity of TECs, resulting in clinically significant immune deficiency disorders or impairment in the adaptive immune response in the body. The present study demonstrated that fish collagen peptides (FCP) increase cell viability, reduce intracellular levels of reactive oxygen species (ROS), and impede apoptosis by repressing the expression of Bax and Bad and the release of cytochrome c, and by upregulating the expression of Bcl-2 and Bcl-xL in cisplatin-treated TECs. These inhibitory effects of FCP on TEC damage occur via the suppression of ROS generation and MAPK (p38 MAPK, JNK, and ERK) activity. Taken together, our data suggest that FCP can be used as a promising protective agent against cytotoxic insults- or ROS-mediated TEC injury. Furthermore, our findings provide new insights into a therapeutic approach for the future application of FCP in the prevention and treatment of various types of oxidative- or cytotoxic stress-related cell injury in TECs as well as age-related or acute thymus involution.

Estimation of the repair efficiency of collagen matrices on the model of thermal burn

Background. In the world, dozens of new local wound healing agents are developed and improved every year, which undergo preliminary tests on laboratory animals due to the presence of common phases of the course of the wound process with humans.

The aim of the study was to evaluate the wound healing effect of matrices obtained on the basis of the recycling of collagen-containing waste.

Materials and methods. Collagen matrices are obtained from substandard leather raw materials subjected to treatment with fermented milk composition (KM1) and lactic acid (KM2). The wound healing effect was studied on the model of thermal burns on Wistar rats in 5 groups: 1st – control (natural wound healing); 2nd – experimental 1 (processing KM1); 3rd – experimental 2 (processing KM2); 4th – experimental 3, comparison group (“Levomekol”) and 5th – intact animals (normal, without burns). Wound healing was assessed by the results of planimetry on days 1, 3, 5, 7, 9, and 13 and by histological analysis of the skin tissue on days 6, 13, and 20. On days 6 and 13, the summary antioxidant activity, the total content of leukocytes, erythrocytes, the activity of the catalase enzyme, and the content of malondialdehyde were determined in the blood of rats.

Results. With thermal damage to the skin, an IIIA degree burn was formed, accompanied by the development of dry coagulation necrosis. The use of collagen matrices restored the total content of leukocytes, reduced the area of the burn wound, normalized the content of malondialdehyde, the total antioxidant activity and the activity of catalase in the blood. Histomorphometric studies have confirmed the dynamics of skin tissue recovery after a burn. The effectiveness of the use of matrices was comparable to the pharmacopoeial drug “Levomekol”. A higher wound healing effect was noted when using the KM1 matrix.

Conclusion. On the model of thermal burn, the wound-healing effect of collagen matrices was established, as evidenced by the results of restoring the number of leukocytes, reducing the area of the burn wound and restoring the histostructure of the skin. One of the molecular and cellular mechanisms of wound healing is the inhibition of lipid peroxidation reactions and the restoration of the antioxidant potential of the body. 

Seventeen novel angiotensin converting enzyme (ACE) inhibitory peptides from protein hydrolysate of Mytilus edulis: Isolation, identification, molecular docking study, and protective function on HUVECs

In the study, seventeen angiotensin converting enzyme (ACE) inhibitory peptides were isolated from protein hydrolysate of blue mussel (Mytilus edulis) and identified as MFR, MFV, FV, KP, QP, QVK, IK,...

The Bioactivity Prediction of Peptides from Tuna Skin Collagen Using Integrated Method Combining In Vitro and In Silico

The hydrolysates and peptide fractions of bigeye tuna (Thunnus obesus) skin collagen have been successfully studied. The hydrolysates (HPA, HPN, HPS, HBA, HBN, HBS) were the result of the hydrolysis of collagen using alcalase, neutrase, and savinase. The peptide fractions (PPA, PPN, PPS, PBA, PBN, PBS) were the fractions obtained following ultrafiltration of the hydrolysates. The antioxidant activities of the hydrolysates and peptide fractions were studied using the DPPH method. The effects of collagen types, enzymes, and molecular sizes on the antioxidant activities were analyzed using profile plots analysis. The amino acid sequences of the peptides in the fraction with the highest antioxidant activity were analyzed using LC-MS/MS. Finally, their bioactivity and characteristics were studied using in silico analysis. The hydrolysates and peptide fractions provided antioxidant activity (6.17-135.40 µmol AAE/g protein). The lower molecular weight fraction had higher antioxidant activity. Collagen from pepsin treatment produced higher activity than that of bromelain treatment. The fraction from collagen hydrolysates by savinase treatment had the highest activity compared to neutrase and alcalase treatments. The peptides in the PBN and PPS fractions of <3 kDa had antidiabetic, antihypertensive and antioxidant activities. In conclusion, they have the potential to be used in food and health applications.

Redox-Mediated Artificial Non-Enzymatic Antioxidant MXene Nanoplatforms for Acute Kidney Injury Alleviation

Acute kidney injury (AKI), as a common oxidative stress-related renal disease, causes high mortality in clinics annually, and many other clinical diseases, including the pandemic COVID-19, have a high potential to cause AKI, yet only rehydration, renal dialysis, and other supportive therapies are available for AKI in the clinics. Nanotechnology-mediated antioxidant therapy represents a promising therapeutic strategy for AKI treatment. However, current enzyme-mimicking nanoantioxidants show poor biocompatibility and biodegradability, as well as non-specific ROS level regulation, further potentially causing deleterious adverse effects. Herein, the authors report a novel non-enzymatic antioxidant strategy based on ultrathin Ti3 C2 -PVP nanosheets (TPNS) with excellent biocompatibility and great chemical reactivity toward multiple ROS for AKI treatment. These TPNS nanosheets exhibit enzyme/ROS-triggered biodegradability and broad-spectrum ROS scavenging ability through the readily occurring redox reaction between Ti3 C2 and various ROS, as verified by theoretical calculations. Furthermore, both in vivo and in vitro experiments demonstrate that TPNS can serve as efficient antioxidant platforms to scavenge the overexpressed ROS and subsequently suppress oxidative stress-induced inflammatory response through inhibition of NF-κB signal pathway for AKI treatment. This study highlights a new type of therapeutic agent, that is, the redox-mediated non-enzymatic antioxidant MXene nanoplatforms in treatment of AKI and other ROS-associated diseases.

RM12 similar to substance P from tachykinin of freshwater murrel Channa striatus influence intracellular ROS in vitro fish erythrocytes and developmental toxicity and antioxidant enzymes in vivo zebrafish embryo

In this study, substance P, an antioxidant peptide of tachykinin, was identified using bioinformatics tools from the earlier established muscle transcriptome of a freshwater murrel Channa striatus and the peptide was named RM12. The antioxidant properties of RM12 were screened using various colorimetric assays. The toxicity of RM12 was experimented using fish erythrocytes, and it is observed that the maximum concentration (320 μM) of RM12 was found to have 15 or 20% of hemolytic activity; however, it was not significant with other tested concentrations (10, 20, 40, 80, and 160 μM). Further, the in vivo antioxidant properties of RM12 were experimented on zebrafish embryo, the intracellular ROS level was estimated by 5 mM H₂O₂ stress in the zebrafish embryo, and inhibition of apoptosis was evaluated. The antioxidant enzymes were extracted from the H₂O₂-stressed zebrafish embryo, and the intracellular ROS was eliminated due to RM12. Collectively, the experiment showed that the substance P from the freshwater murrel C. striatus possessed potent antioxidant properties; thus, it can further be focused to develop it as antioxidant molecule in aquaculture organisms.

The Pro-Gly or Hyp-Gly Containing Peptides from Absorbates of Fish Skin Collagen Hydrolysates Inhibit Platelet Aggregation and Target P2Y12 Receptor by Molecular Docking

Previous studies found that the collagen hydrolysates of fish skin have antiplatelet activity, but this component remained unknown. In this study, eleven peptides were isolated and identified in the absorbates of Alcalase-hydrolysates and Protamex®-hydrolysates of skin collagen of H. Molitrix by reverse-phase C18 column and HPLC-MS/MS. Nine of them contained a Pro-Gly (PG) or Hyp-Gly (OG) sequence and significantly inhibited ADP-induced platelet aggregation in vitro, which suggested that the PG(OG) sequence is the core sequence of collagen peptides with antiplatelet activity. Among them, OGSA has the strongest inhibiting activities against ADP-induced platelet aggregation in vitro (IC50 = 0.63 mM), and OGSA inhibited the thrombus formation in rats at a dose of 200 μM/kg.bw with no risk of bleeding. The molecular docking results implied that the OG-containing peptides might target the P2Y12 receptor and form hydrogen bonds with the key sites Cys97, Ser101, and Lys179. As the sequence PG(OG) is abundant in the collagen amino acid sequence of H. Molitrix, the collagen hydrolysates of H. Molitrix might have great potential for being developed as dietary supplements to prevent cardiovascular diseases in the future.

Effect of Fish Bone Bioactive Peptides on Oxidative, Inflammatory and Pigmentation Processes Triggered by UVB Irradiation in Skin Cells

In the present study, we evaluated for the first time the photoprotective effect of fish bone bioactive peptides (FBBP) preparation isolated from silver carp (Hypophthalmichthys molitrix) discarded tissue using in vitro experimental models of skin cells exposed to ultraviolet B (UVB) irradiation and stressing agents. FBBP preparation was obtained by papain treatment of minced bones and centrifugal ultrafiltration, and the molecular weight (MW) distribution was characterized by size exclusion and reversed-phase high performance liquid chromatography (RP-HPLC). In vitro assessment of the effect of FBBP pretreatment in UVB-irradiated L929 fibroblasts and HaCaT keratinocytes revealed their cytoprotective activity. Their capacity to efficiently reduce reactive oxygen species (ROS) production and lipid peroxidation varied in a dose-dependent manner, and it was greater in fibroblasts. A decrease of proinflammatory cytokines secretion, in particular of tumor necrosis factor alpha (TNF-α), was found after FBBP pretreatment of THP-1-derived inflamed macrophages. Melanin production and tyrosinase activity investigated in UVB-irradiated Mel-Juso cells were lowered in direct relation to FBBP concentrations. FBBP fractions with high radical scavenging activity were separated by ion exchange chromatography, and two collagenic sequences were identified. All these results offer new scientific data on aquaculture fish bone-derived peptides confirming their ability to control the antioxidant, anti-inflammatory and pigmentation processes developed during UV irradiation of skin cells and recommend their use as valuable natural ingredients of photoprotective cosmeceutical products.

Antioxidant and functional properties of cowhide collagen peptides

In the present study, antioxidant activities and functional properties of cowhide collagen antioxidant peptides (CCAPs) with different molecular weight (MW) were investigated. The optimum preparation conditions of CCAPs were hydrolysis time of 1.53 hr, temperature of 54.9 °C, pH 7.38, and neutral enzyme to trypsin ratio of 0.048 g: 0.016 g according to single factor test and response surface methodology (RSM). Three fractions (CCAP-I, CCAP-II, and CCAP-III) were obtained by ultrafiltration and lyophilization. Antioxidant activities revealed that CCAP-III had high reducing power activity (0.323 ± 0.035) and scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (64.30 ± 5.99%), 2,2-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radicals (75.25 ± 3.14%), and hydroxyl radicals (68.26 ± 6.74%) compared to the other fractions. In addition, LC-MS/MS analysis showed that Ala-Gly-Glu-Arg, Gly-Ile-Ala-Gly-Glu-Arg, Gly-Pro-Ala-Gly-Pro-Ala-Gly-Pro-Arg, Gly-Val-Val-Gly-Pro-Glu-Gly-Ala-Arg and Gly-Phe-Ser-Gly-Leu-Asp-Gly-Ala-Lys were the major peptides of CCAP-III. CCAP-III showed good hygroscopicity (HYG), water holding capacity (WHC), and oil holding capacity (OHC) when compared with CCAP-I and CCAP-II. However, CCAP-II has great emulsifying properties, and CCAP-I has excellent foaming properties. Therefore, CCAPs can be used as a promising source of functional peptides with antioxidant properties. PRACTICAL APPLICATION: This study demonstrated the peptides of cowhide collagen has superior antioxidant and functional properties. This study provided a scientific basis for the preparation of antioxidant peptides from cowhide collagen.

Fish Waste: From Problem to Valuable Resource

Following the growth of the global population and the subsequent rapid increase in urbanization and industrialization, the fisheries and aquaculture production has seen a massive increase driven mainly by the development of fishing technologies. Accordingly, a remarkable increase in the amount of fish waste has been produced around the world; it has been estimated that about two-thirds of the total amount of fish is discarded as waste, creating huge economic and environmental concerns. For this reason, the disposal and recycling of these wastes has become a key issue to be resolved. With the growing attention of the circular economy, the exploitation of underused or discarded marine material can represent a sustainable strategy for the realization of a circular bioeconomy, with the production of materials with high added value. In this study, we underline the enormous role that fish waste can have in the socio-economic sector. This review presents the different compounds with high commercial value obtained by fish byproducts, including collagen, enzymes, and bioactive peptides, and lists their possible applications in different fields.

Effect of Collagen Tripeptide and Adjusting for Climate Change on Skin Hydration in Middle-Aged Women: A Randomized, Double-Blind, Placebo-Controlled Trial

Introduction: Although collagen is widely used in various forms as a functional ingredient in skin care products, the effect of oral supplementation of collagen tripeptides (CTPs) on human skin is unclear. Moreover, the majority of the positive outcomes of CTP reported so far have not considered the effect of weather conditions. Therefore, we tested the effect of CTP and adjusting for climate change on skin properties in middle-aged women.

Materials and Methods: A randomized controlled trial was conducted with 84 women between 40 and 60 years of age. Participants were randomized to receive placebo or 1,000 mg CTP daily for 12 weeks. CTP was prepared from the skin of Nile Tilapia by the digestion method using collagenase from non-pathogenic bacteria of the genus Bacillus. Skin hydration, wrinkling, and elasticity were assessed at baseline and after 6 and 12 weeks with adjustments for temperature, humidity, and ultraviolet A exposure during the evaluation time using weather data from the regional meteorological office.

Results: Of the 82 participants, 74 completed the trial without adverse effects. Compared with the control group, trans-epidermal water loss was reduced more in the CTP group after 12 weeks (P < 0.05). At 12 weeks, even after adjustment for humidity, temperature, and UVA in the region, the difference of the two groups in TEWL remained statistically significant (adjusted for humidity and temperature, P = 0.024; adjusted for UVA, P = 0.032; adjusted for temperature, high temperature, and ultraviolet A, P = 0.031). In terms of skin hydration, more improvement was evident in the CTP group than in the control group. In the subgroup analysis, subjects under 50 years of age showed a significant improvement in total score and moisture in the subjective skin improvement questionnaire after taking CTP for 12 weeks. Application of CTP was well-tolerated, and no notable adverse effect was reported from both groups.

Discussion: Our findings suggest that oral ingestion of CTP from the Skin of Nile Tilapia (Oreochromis niloticus) is well-tolerated and helps reduce water loss in in middle-aged women.

Clinical Trial Registration:www.clinicaltrials.gov/, Identifier: NCT03505684.

Validation of Three Different Sterilization Methods of Tilapia Skin Dressing: Impact on Microbiological Enumeration and Collagen Content

Tilapia fish skin has demonstrated promise as a stable and practical biological dressing to be used in wound and burn management. However, the appropriate sterilization technique of the Tilapia fish skin is crucial before its clinical application. The standard sterilization technique must eliminate harmful pathogens but maintain the structural and biochemical properties that could compromise the dressing function. This study investigated and compared the efficiency of three sterilizing agents; chlorhexidine gluconate 4% (CHG), povidone iodine 10% (PVP-I), and silver nanoparticles (25 μg/mL) (AgNPs), at three different times (5, 10, and 15 min) on Tilapia fish skin based on the microbial count, histological and collagen properties. Among the sterilization procedures, AgNPs showed rapid and complete antimicrobial activity, with a 100% reduction in microbial growth of the fish skin throughout the treated times. Furthermore, AgNPs did not impair the cellular structure or collagen fibers content of the fish skin. However, CHG and PVP-I caused alterations in the collagen content. This study demonstrated that the AgNPs treatment of Tilapia fish skin provided sterile skin while preserving the histological properties and structural integrity. These findings provide an efficient and quick sterilization method suitable for Tilapia fish skin that could be adopted as a biological dressing.

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

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

Human collagen alpha-2 type I stimulates collagen synthesis, wound healing, and elastin production in normal human dermal fibroblasts (HDFs)

Skin aging appears to be the result of overlapping intrinsic (including genetic and hormonal factors) and extrinsic (external environment including chronic light exposure, chemicals, and toxins) processes. These factors cause decreases in the synthesis of collagen type I and elastin in fibroblasts and increases in the melanin in melanocytes. Collagen Type I is the most abundant type of collagen and is a major structural protein in human body tissues. In previous studies, many products containing collagen derived from land and marine animals as well as other sources have been used for a wide range of purposes in cosmetics and food. However, to our knowledge, the effects of human collagen-derived peptides on improvements in skin condition have not been investigated. Here we isolate and identify the domain of a human COL1A2-derived protein which promotes fibroblast cell proliferation and collagen type I synthesis. This human COL 1A2-derived peptide enhances wound healing and elastin production. Finally, the human collagen alpha-2 type I-derived peptide (SMM) ameliorates collagen type I synthesis, cell proliferation, cell migration, and elastin synthesis, supporting a significant anti-wrinkle effect. Collectively, these results demonstrate that human collagen alpha-2 type I-derived peptides is practically accessible in both cosmetics and food, with the goal of improving skin condition.

Antioxidant mechanism, antibacterial activity, and functional characterization of peptide fractions obtained from barred mackerel gelatin with a focus on application in carbonated beverages

The present study aimed to use fish by-products to generate gelatin peptides with potential applications in carbonated beverages. After ultrafiltration, the F < 3 kDa (fraction < 3 kDa) showed the highest peptide concentration (227.22 mg/g) as well as antibacterial (MIC of ≤ 0.5 mg/mL) and antioxidant activities, including hydroxyl and superoxide radical scavenging, ferrous chelation, and ferric reduction (with IC₅₀ values of 0.88, 1.04, 0.50 mg/mL, and 0.58, respectively). 2,2-diphenyl-1-picrylhydrazyl scavenging was the highest in the 3 < F < 10 kDa (IC₅₀ of 0.64 mg/mL). In vitro gastrointestinal digestion significantly decreased all biological activities. Solubility, water holding capacity, and emulsifying activity of the F < 3 kDa were the highest while foaming properties and overfoaming were reversibly related to the molecular weight. All abovementioned properties, in addition to in vitro cytotoxicity analysis in different cell lines and better flavor characteristics, indicated that the F < 3 kDa could be safely and properly used as an ingredient for the fortification of carbonated beverages.

Physicochemical Properties of Collagen from Acaudina Molpadioides and Its Protective Effects against H2O2-Induced Injury in RAW264.7 Cells

Collagen is a promising biomaterial used in the beauty and biomedical industries. In this study, the physicochemical characterization, antioxidant activities, and protective effects against H₂O₂-induced injury of collagen isolated from Acaudina molpadioides were investigated. The amino acid composition analysis showed that the collagen was rich in glycine (Gly), alanine (Ala), and glutamic acid (Glu), but poor in tyrosine (Tyr) and phenylalanine (Phe). Zeta potential analysis revealed that the isoelectric point (pI) of collagen from Acaudina molpadioides was about 4.25. It possessed moderate scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals in a dose-dependent manner. In addition, the collagen was able to effectively improve cell viability and morphology, inhibit the production of Malondialdehyde (MDA), and increase the activities of Superoxide Dismutase (SOD) and Glutathione Peroxidase (GSH-Px) in cultured RAW264.7 cells, resulting in a protective effect against H₂O₂-induced injury. Overall, the results showed that collagen extracted from A. molpadioides has promising prospects in the beauty and cosmetics industries.

Collagen formula with Djulis for improvement of skin hydration, brightness, texture, crow's feet, and collagen content: A double-blind, randomized, placebo-controlled trial

BACKGROUND

The efficacy of Djulis for skin care is currently based on cellular or animal models, and the clinical aspect is not in place.

AIM

This clinical study is to investigate the synergistic effect of fish collagen and Djulis (Chenopodium formosanum Koidz.) for improvement of skin parameters. We used the combination of hydrolyzed collagen and Djulis to develop a new functional formula for skin improvement.

PATIENTS/METHODS

Fifty volunteers were randomly allocated (in a 1:1 ratio) to the placebo or collagen drink group. Volunteers were required to consume a 50 mL of a collagen drink or placebo drink daily for 8 weeks. For measurements, the indexes of skin conditions were measured at the baseline and 4 and 8 weeks.

RESULTS

The improvements of skin hydration, brightness, crow's feet, texture, wrinkles, pores, spots, and collagen content after 8 weeks in collagen group were 17.8%, 5.4%, 14.9%, 9.9%, 29.3%, 10.4%, 9.9%, and 22.3%, respectively. Noticeably, over 68% of subjects got improved for their skin parameters after 8-week intake of collagen drink. The improvement levels indicated competitive skin improvement effects in comparison with previous studies.

CONCLUSION

This clinical study demonstrates the synergistic effect of fish collagen and Djulis (the main components) for the substantial improvements in hydration, brightness, crow's feet, texture, wrinkles, pores, surface spots, and collagen content in skin. The collagen drink comprehensively improved skin parameters for most subjects after 4-week intake and manifested competitive efficiency in comparison with other similar studies. We convince that the collagen drink may delay skin aging process and improve skin aging parameters.

Ultrasmall copper-based nanoparticles for reactive oxygen species scavenging and alleviation of inflammation related diseases

Oxidative stress is associated with many acute and chronic inflammatory diseases, yet limited treatment is currently available clinically. The development of enzyme-mimicking nanomaterials (nanozymes) with good reactive oxygen species (ROS) scavenging ability and biocompatibility is a promising way for the treatment of ROS-related inflammation. Herein we report a simple and efficient one-step development of ultrasmall Cu_5.4O nanoparticles (Cu_5.4O USNPs) with multiple enzyme-mimicking and broad-spectrum ROS scavenging ability for the treatment of ROS-related diseases. Cu_5.4O USNPs simultaneously possessing catalase-, superoxide dismutase-, and glutathione peroxidase-mimicking enzyme properties exhibit cytoprotective effects against ROS-mediated damage at extremely low dosage and significantly improve treatment outcomes in acute kidney injury, acute liver injury and wound healing. Meanwhile, the ultrasmall size of Cu_5.4O USNPs enables rapid renal clearance of the nanomaterial, guaranteeing the biocompatibility. The protective effect and good biocompatibility of Cu_5.4O USNPs will facilitate clinical treatment of ROS-related diseases and enable the development of next-generation nanozymes.

Antioxidant Peptides from Collagen Hydrolysate of Redlip Croaker (Pseudosciaena polyactis) Scales: Preparation, Characterization, and Cytoprotective Effects on H2O2-Damaged HepG2 Cells

Bioactive peptides from fish collagens with antioxidant properties have become a topic of great interest for health, food, and processing/preservation industries. To explore the high-value utilized way of scales produced during the fish processing, collagen hydrolysates of redlip croaker (Pseudosciaena polyactis) scales were prepared using six different proteases, and the hydrolysate (RSCH) prepared using neutrase showed the highest degree of hydrolysis (21.36 ± 1.18%) and 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging activity (30.97 ± 1.56%) among the six hydrolysates. Subsequently, six antioxidant peptides were purified from RSCH using membrane ultrafiltration and serial chromatography, and their amino acid sequences were identified as DGPEGR, GPEGPMGLE, EGPFGPEG, YGPDGPTG, GFIGPTE, and IGPLGA with molecular masses of 629.61, 885.95, 788.96, 762.75, 733.80, and 526.61 Da, respectively. Among six collagen peptides, GPEGPMGLE, EGPFGPEG, and GFIGPTE exhibited the strongest scavenging activities on DPPH· radical (EC₅₀ 0.59, 0.37, and 0.45 mg/mL), hydroxyl radical (EC₅₀ 0.45, 0.33, and 0.32 mg/mL), and superoxide anion radical (EC₅₀ 0.62, 0.47, and 0.74 mg/mL). GPEGPMGLE, EGPFGPEG, and GFIGPTE showed high inhibiting ability on lipid peroxidation in a linoleic acid model system and protective activities on oxidation-damaged DNA. More importantly, GPEGPMGLE, EGPFGPEG, and GFIGPTE could protect HepG2 cells from H₂O₂-induced oxidative damage through decreasing the levels of reactive oxygen species (ROS) and MDA and activating intracellular antioxidant enzymes of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). These results suggested that six collagen peptides (RCP1–RCP6), especially GPEGPMGLE, EGPFGPEG, and GFIGPTE, might serve as potential antioxidants applied in nutraceutical and pharmaceutical products.

Antioxidant Peptides from the Protein Hydrolysate of Monkfish (Lophius litulon) Muscle: Purification, Identification, and Cytoprotective Function on HepG2 Cells Damage by H2O2

In the work, defatted muscle proteins of monkfish (Lophius litulon) were separately hydrolyzed by pepsin, trypsin, and in vitro gastrointestinal (GI) digestion methods, and antioxidant peptides were isolated from proteins hydrolysate of monkfish muscle using ultrafiltration and chromatography processes. The antioxidant activities of isolated peptides were evaluated using radical scavenging and lipid peroxidation assays and H2O2-induced model of HepG2 cells. In which, the cell viability, reactive oxygen species (ROS) content, and antioxidant enzymes and malondialdehyde (MDA) levels were measured for evaluating the protective extent on HepG2 cells damaged by H2O2. The results indicated that the hydrolysate (MPTH) prepared using in vitro GI digestion method showed the highest degree of hydrolysis (27.24 ± 1.57%) and scavenging activity on a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (44.54 ± 3.12%) and hydroxyl radical (41.32 ± 2.73%) at the concentration of 5 mg protein/mL among the three hydrolysates. Subsequently, thirteen antioxidant peptides (MMP-1 to MMP-13) were isolated from MPTH. According to their DPPH radical and hydroxyl radical scavenging activity, three peptides with the highest antioxidant activity were selected and identified as EDIVCW (MMP-4), MEPVW (MMP-7), and YWDAW (MMP-12) with molecular weights of 763.82, 660.75, and 739.75 Da, respectively. EDIVCW, MEPVW, and YWDAW showed high scavenging activities on DPPH radical (EC50 0.39, 0.62, and 0.51 mg/mL, respectively), hydroxyl radical (EC50 0.61, 0.38, and 0.32 mg/mL, respectively), and superoxide anion radical (EC50 0.76, 0.94, 0.48 mg/mL, respectively). EDIVCW and YWDAW showed equivalent inhibiting ability on lipid peroxidation with glutathione in the linoleic acid model system. Moreover, EDIVCW, MEPVW, and YWDAW had no cytotoxicity to HepG2 cells at the concentration of 100.0 µM and could concentration-dependently protect HepG2 cells from H2O2-induced oxidative damage through decreasing the levels of reactive oxygen species (ROS) and MDA and activating intracellular antioxidant enzymes of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). These present results indicated that the protein hydrolysate and isolated antioxidant peptides from monkfish muscle, especially YWDAW could serve as powerful antioxidants applied in the treatment of some liver diseases and healthcare products associated with oxidative stress.

Isolation and identification of antioxidant peptides from tartary buckwheat albumin (Fagopyrum tataricum Gaertn.) and their antioxidant activities

Tartary buckwheat (Fagopyrum tataricum Gaertn.) albumin was hydrolyzed by alkaline protease, and three new antioxidant peptides (P1, P2, and P3) were successfully separated from the hydrolysate (TBAH). The sequences of the three antioxidant peptides were Gly-Glu-Val-Pro-Trp (GEVPW), Tyr-Met-Glu-Asn-Phe (YMENF), and Ala-Phe-Tyr-Arg-Trp (AFYRW), and their molecular weights were 586.65, 702.79, and 741.85 Da, respectively. All three peptides have a good antioxidant capacity, and P3 (AFYRW) demonstrates the best antioxidant activity of the three. The IC₅₀ values of AFYRW for scavenging hydroxyl radicals (OH·) and (1,1-diphenyl-2-picrylhydrazyl) DPPH· free radicals were 0.65 and 0.64 mM, respectively. In addition, AFYRW exhibits the strongest lipid peroxidation inhibition ability and the highest reducing power. The results of this research indicate that the three isolated peptides can be used in the development of various antioxidant additives in the food and pharmaceutical industries.

In Vitro Antioxidant Activity of Peptides from Simulated Gastro-Intestinal Digestion Products of Cyprinus carpio haematopterus Scale Gelatin

A two-stage simulated gastro-intestinal (GI) digestion model (2 h pepsin treatment and subsequent 2 h pancreatin treatment at 37 °C) was used to explore the antioxidant activity of the digested products of Cyprinus carpio haematopterus scale gelatin with different molecular weights (MW). From the gastric phase to the intestinal phase, the hydrolysis degree of the products increased from 2.6 ± 0.4% to 16.9 ± 0.7%. The fraction of 0–1 kDa (JCP3) exhibited the best antioxidant activities in hydroxyl radical scavenging, reducing power, and metal chelating activity. The fraction of 1–3 kDa (JCP2) exhibited the best 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. However, the fractions of 0–1 kDa (JCP3) and 1–3 kDa (JCP2) showed similar inhibitory activity of lipid peroxidation. The results indicated that Cyprinus carpio haematopterus scale gelatin can be digested in the gastrointestinal tract. Furthermore, the digested products had antioxidant activity.