Anti-Fatigue Effect by Peptide Fraction from Protein Hydrolysate of Croceine Croaker (Pseudosciaena crocea) Swim Bladder through Inhibiting the Oxidative Reactions including DNA Damage

Swim bladder-derived biomaterials: structures, compositions, properties, modifications, and biomedical applications

Animal-derived biomaterials have been extensively employed in clinical practice owing to their compositional and structural similarities with those of human tissues and organs, exhibiting good mechanical properties and biocompatibility, and extensive sources. However, there is an associated risk of infection with pathogenic microorganisms after the implantation of tissues from pigs, cattle, and other mammals in humans. Therefore, researchers have begun to explore the development of non-mammalian regenerative biomaterials. Among these is the swim bladder, a fish-derived biomaterial that is rapidly used in various fields of biomedicine because of its high collagen, elastin, and polysaccharide content. However, relevant reviews on the biomedical applications of swim bladders as effective biomaterials are lacking. Therefore, based on our previous research and in-depth understanding of this field, this review describes the structures and compositions, properties, and modifications of the swim bladder, with their direct (including soft tissue repair, dural repair, cardiovascular repair, and edible and pharmaceutical fish maw) and indirect applications (including extracted collagen peptides with smaller molecular weights, and collagen or gelatin with higher molecular weights used for hydrogels, and biological adhesives or glues) in the field of biomedicine in recent years. This review provides insights into the use of swim bladders as source of biomaterial; hence, it can aid biomedicine scholars by providing directions for advancements in this field.

Characterization of volatile flavor compounds from fish maw soaked in five different seasonings

In this study, sensory evaluation, electronic nose, and HS-GC-IMS were used to investigate the effects of different seasonings (deionized water, onion, ginger, Sichuan pepper, and mixed seasonings) on the flavor of fish maw. The results showed that the volatile compounds of fish maw soaked in different seasonings were mainly organic sulfides and aromatic compounds. A total of 95 volatile compounds were identified, including 25 aldehydes, 23 olefins, 19 alcohols, 11 esters, 9 ketones, 3 acids, 2 sulfides, 1 furan, 1 ether and 1 ketoxime. Sichuan pepper group and mixed seasoning group had the most significant changes in volatile components, and had the most effective improvement on the flavor of fish maw compared with other groups. These findings will provide reference for producing high quality fish maw and improving its flavor quality. These findings will provide feasible theoretical support for the pretreatment and exploration of fish maw products in the future.

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

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

Anti-fatigue effect of glycoprotein from hairtail (Trichiurus lepturus) by-products in a behavioral mouse model

Hairtail (Trichiurus lepturus) is a kind of abundant marine fish, and its by-products contain rich protein resources, which can be better exploited and utilized in the food industry. In this study, the glycoprotein of hairtail by-products (GHB) was extracted using ultrasonic-assisted salt solution extraction with hairtail by-products as the raw material. The anti-fatigue effect of GHB was explored by mouse behavior experiments (shuttle box test, open field test and load swimming test). The results showed that the active escape times of the GHB group increased compared with the blank group in the shuttle box test, and the GHB group stayed in the central area for more time in the open field test. At the same time, the exhaustive swimming time of high-dose-group mice was 122.01% longer than that of the blank control group. GHB can improve the memory learning ability and activity of mice, and exert its anti-fatigue effect by eliminating excessive free radicals, slowing the metabolism of amino acids and proteins, and increasing glycogen reserves. This study provides a theoretical basis for the function mechanism of glycoprotein of hairtail by-products and the development of supplementary material in functional foods.

Diarrhea accompanies intestinal inflammation and intestinal mucosal microbiota dysbiosis during fatigue combined with a high-fat diet

OBJECTIVE

It was reported fatigue or a high-fat diet triggers diarrhea, and intestinal microbiota may play central roles in diarrhea. Therefore, we investigated the association between the intestinal mucosal microbiota and the intestinal mucosal barrier from fatigue combined with a high-fat diet.

METHOD

This study divided the Specific pathogen-free (SPF) male mice into the normal group (MCN) and the standing united lard group (MSLD). The MSLD group stood on water environment platform box for 4 h/day for 14 days, and 0.4 mL lard was gavaged from day 8, twice daily for 7 days.

RESULT

After 14 days, Mice in the MSLD group showed diarrhea symptoms. The pathological analysis showed structural damage to the small intestine in the MSLD group, with an increasing trend of interleukin-6 (IL-6) and IL-17, and inflammation accompanied by structural damage to the intestine. Fatigue combined with a high-fat diet considerably decreased Limosilactobacillus vaginalis and Limosilactobacillus reuteri, and among them, Limosilactobacillus reuteri positively associated with Muc2 and negatively with IL-6.

CONCLUSION

The interactions between Limosilactobacillus reuteri and intestinal inflammation might be involved in the process of intestinal mucosal barrier impairment in fatigue combined with high-fat diet-induced diarrhea.

A Thermostable Type I Collagen from Swim Bladder of Silver Carp (Hypophthalmichthys molitrix)

As a major component of the extracellular matrix, collagen has been used as a biomaterial for many purposes including tissue engineering. Commercial collagen derived from mammals is associated with a risk of prion diseases and religious restrictions, while fish-derived collagen can avoid such issues. In addition, fish-derived collagen is widely available and low-cost; however, it often suffers from poor thermal stability, which limits its biomedical application. In this study, collagen with a high thermal stability was successfully extracted from the swim bladder of silver carp (Hypophthalmichthys molitrix) (SCC). The results demonstrated that it was a type I collagen with high purity and well-preserved triple-helix structure. Amino acid composition assay showed that the amounts of threonine, methionine, isoleucine and phenylalanine in the collagen of swim bladder of silver carp were higher than those of bovine pericardium. After adding salt solution, swim-bladder-derived collagen could form fine and dense collagen fibers. In particular, SCC exhibited a higher thermal denaturation temperature (40.08 °C) compared with collagens from the swim bladder of grass carp (Ctenopharyngodon idellus) (GCC, 34.40 °C), bovine pericardium (BPC, 34.47 °C) and mouse tail (MTC, 37.11 °C). Furthermore, SCC also showed DPPH radical scavenging ability and reducing power. These results indicate that SCC presents a promising alternative source of mammalian collagen for pharmaceutical and biomedical applications.

The Anti-Fatigue Effect of Glycoprotein from Hairtail Fish (Trichiurus lepturus) on BALB/c Mice

Fatigue is related to a variety of chronic diseases and has become a hot research topic in recent years. Various bioactive components have been extracted from hairtail fish (Trichiurus lepturus); however, none of these studies involved the anti-fatigue activity of hairtail fish glycoprotein (HGP). Thus, antioxidant experiments were conducted in vitro, and the anti-fatigue activity of HGP was further evaluated in BALB/c mice. The effects of HGP on the behavior of BALB/c mice were verified by classical behavioral experiments, and the indicators related to anti-fatigue activity were detected. The results showed that the antioxidant capacity in vitro of HGP increased gradually in the concentration range of 10 to 100 mg/mL. HGP improved the exercise ability of the mice. HGP was also found to significantly (p < 0.05) reduce the serum levels of lactate dehydrogenase (LDH), blood lactic acid (BLA), blood urea nitrogen (BUN), and creatine kinase (CK). The contents of liver glycogen (LG) and muscle glycogen (MG) were also significantly (p < 0.05) increased by HGP. Malondialdehyde (MDA) content in the serum and brains of the mice was significantly (p < 0.05) reduced and catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase (SOD) were significantly (p < 0.05) increased by HGP, especially in the middle- and high-dose groups. These results enhance our understanding of the anti-fatigue function of HGP and lay an important foundation for the further development and utilization of hairtail fish resources.

Milk Fat Globule Membrane Relieves Fatigue via Regulation of Oxidative Stress and Gut Microbiota in BALB/c Mice

Milk fat globule membranes (MFGMs) are complex structures that incorporate bioactive proteins and lipids to assist in infant development. However, the antifatigue and antioxidant potentials of MFGM have not been investigated. In this study, repeated force swimming measured fatigue in male BALB/c mice fed MFGM and saline for 18 weeks. The MFGM supplementation increased the time to exhaustion by 42.7% at 6 weeks and 30.6% at 14 weeks (p < 0.05). Fatigue and injury-related biomarkers, including blood glucose, lactic acid, and lactate dehydrogenase, were ameliorated after free swimming (p < 0.05). The activity of antioxidant enzymes in blood serum increased at 18 weeks, while malondialdehyde (MDA) content decreased by 45.0% after the MFGM supplementation (p < 0.05). The Pearson correlation analysis showed a high correlation between fatigue-related indices and antioxidant levels. The increased protein expression of hepatic Nrf2 reduced the protein expression of Caspase-3 in the gastrocnemius muscle (p < 0.05). Moreover, the MFGM supplementation increased the relative abundance of Bacteroides, Butyricimonas, and Anaerostipes. Our results demonstrate that MFGM may maintain redox homeostasis to relieve fatigue, suggesting the potential application of MFGM as an antifatigue and antioxidant dietary supplement.

Swim Bladder of Farmed Totoaba macdonaldi: A Source of Value-Added Collagen

Finding strategies to use the swim bladder of farmed totoaba (Totoaba macdonaldi) is of the utmost need to reduce waste. Fish swim bladders are rich in collagen; hence, extracting collagen is a promising alternative with benefits for aquaculture of totoaba and the environment. The elemental biochemical composition of totoaba swim bladders, including their proximate and amino acid compositions, was determined. Pepsin-soluble collagen (PSC) was used to extract collagen from swim bladders, and its characteristics were analyzed. Alcalase and papain were used for the preparation of collagen hydrolysates. Swim bladders contained 95% protein, 2.4% fat, and 0.8% ash (on a dry basis). The essential amino acid content was low, but the functional amino acid content was high. The PSC yield was high, at 68% (dry weight). The amino acid composition profile, electrophoretic pattern, and structural integrity analyses of the isolated collagen suggested it is a typical type-I collagen with high purity. The denaturalization temperature was 32.5 °C, probably attributable to the imino acid content (205 residues/1000 residues). Papain-hydrolysates (≤3 kDa) of this collagen exhibited higher radical scavenging activity than Alcalase-hydrolysates. The swim bladder from the farmed totoaba could be an ideal source to produce high-quality type I collagen and may be considered an alternative to conventional collagen sources or bioactive peptides.

Anti-fatigue Effect of Traditional Chinese Medicines: A Review

A third of the world's population suffers from unexplained fatigue, hugely impacting work learning, efficiency, and health. The fatigue development may be a concomitant state of a disease or the side effect of a drug, or muscle fatigue induced by intense exercise. However, there are no authoritative guides or clinical medication recommendations for various fatigue classifications. Traditional Chinese medicines (TCM) are used as dietary supplements or healthcare products with specific anti-fatigue effects. Thus, TCM may be a potential treatment for fatigue. In this review, we outline the pathogenesis of fatigue, awareness of fatigue in Chinese and western medicine, pharmacodynamics mechanism, and substances. Additionally, we offer a comprehensive summary of fatigue and forecast the potential effect of novel herbal-based medicines against fatigue.

Polysaccharides from apple pomace exhibit anti-fatigue activity through increasing glycogen content

The polysaccharides were isolated from apple pomace by hot-water extraction, and their anti-fatigue activity was evaluated in C2C12 muscle myoblasts and male Kunming mice. The purified polysaccharides from apple pomace (PAP) have a molecular weight of 1.74 × 105 Da and were composed of mannose, rhamnose, glucose, galactose and arabinose. In C2C12 myoblasts, PAP showed no cytotoxicity in the concentrations of 0-300 μg/ml. PAP treatment increased the glycogen content, while the ATP content was not affected in C2C12 myoblasts. Further investigation found that the activity and gene expression of glycogen synthase, rather than glycogen phosphorylase, were upregulated by PAP treatment. The studies in vivo showed that PAP treatment did not affect the food intake and weight again in mice. Importantly, PAP prolonged the exhaustive swimming time, increased hepatic and skeletal muscle glycogen levels, and effectively inhibited the accumulation of blood lactic and blood urea nitrogen in mice. Taken together, the results suggested that PAP exhibit anti-fatigue activity in vitro and in vivo through increasing glycogen content.

Peptides from the croceine croaker (Larimichthys crocea) swim bladder attenuate busulfan-induced oligoasthenospermia in mice

CONTEXT

The swim bladder of the croceine croaker is believed to have a therapeutic effect on various diseases. However, there is no research about its effect on mammalian spermatogenesis.

OBJECTIVE

We investigated the swim bladder peptides (SBPs) effect on busulfan-induced oligoasthenospermia in mice.

MATERIALS AND METHODS

We first extracted SBP from protein hydrolysate of the croceine croaker swim bladder, and then five groups of ICR male mice were randomly assigned: control, control + SBP 60 mg/kg, busulfan, busulfan + SBP 30 mg/kg and busulfan + SBP 60 mg/kg. Mice received bilateral intratesticular injections of busulfan to establish oligoasthenospermia model. After treatment with SBP for 4 weeks, testis and epididymis were collected from all mice for further analysis.

RESULTS

After treatment with SBP 30-60 mg/kg for 4 weeks, epididymal sperm concentration and motility increased by 3.9-9.6- and 1.9-2.4-fold than those of oligoasthenospermia mice induced by busulfan. Meanwhile, histology showed that spermatogenic cells decreased, leading to increased lumen diameters and vacuolization in the busulfan group. These features were reversed by SBP treatment. RNA-sequencing analysis revealed that, compared with the busulfan group, Lin28b and Igf2bp1 expression related to germ cell proliferation, increased with a >1.5-fold change after SBP treatment. Additionally, PGK2 and Cfap69 mRNAs associated with sperm motility, also increased with a >1.5-fold change. Furthermore, these findings were validated by quantitative real-time PCR and Western blotting.

DISCUSSION AND CONCLUSIONS

This is the first reported evidence for the therapeutic effect of SBP on oligoasthenospermia. SBP may be a promising drug for oligoasthenospermia in humans.

Molecular Identification of Commercial Fish Maws by DNA Sequencing of 16S rRNA and Cytochrome c Oxidase I Genes

ABSTRACT

Fish maws (dried swim bladders) have long been used for medicinal tonics and as a valuable food resource in Southeast Asia. However, it is difficult to identify the original species of fish maws sold in markets due to a lack of taxonomic characteristics. In the present study, 37 kinds of commercial fish maws from various medicinal material markets were examined, and gene sequences were successfully obtained from ca. 95% of the samples. Partial sequences of the 16S rRNA gene and cytochrome c oxidase I (COI) gene were obtained and used to investigate the origin of these commercial fish maws. Thirty-five specimens belonged to nine species: five croakers and four noncroakers. All species identification was supported by both high homogeneity (98 to 100%) and clear clustering with low within-group Kimura two-parameter divergence scores (0 to 0.04 for 16S rRNA and 0 to 0.07 for COI) and high between-group divergence scores (0.07 to 0.15 for 16S rRNA and 0.11 to 0.24 for COI). Croakers were the predominant species, accounting for 74% of the total fish maw specimens. The large demand for croakers has put some species at the risk of extinction due to overfishing. As a valuable food, fish maw has progressively become more popular and has been used as a substitute for shark fin. The identification results allowed us to learn more about the fish species available on the fish maw market and provided an indicator for possible control of threatened or endangered fish species. A probable correlation between the molecular characteristics and morphological features of fish maws was also found and could provide both consumers and merchants with an important reference for identifying the origin of fish maws.

HIGHLIGHTS

Protein and Sport: Alternative Sources and Strategies for Bioactive and Sustainable Sports Nutrition

Nutrition and sport play an important role in achieving a healthy lifestyle. In addition to the intake of nutrients derived from the normal diet, some sport disciplines require the consumption of supplements that contribute positively to improved athletic performance. Protein intake is important for many aspects related to health, and current evidence suggests that some athletes require increased amounts of this nutrient. On the other hand, society's demand for more environmentally friendly products, focus on the search for alternative food sources more sustainable. This review aims to summarize the latest research on novel strategies and sources for greener and functional supplementation in sport nutrition. Alternative protein sources such as insects, plants or mycoproteins have proven to be an interesting substrate due to their high added value in terms of bioactivity and sustainability. Protein hydrolysis has proven to be a very useful technology to revalue by-products, such as collagen, by producing bioactive peptides beneficial on athletes performance and sport-related complications. In addition, it has been observed that certain amino acids from plant sources, as citrulline or theanine, can have an ergogenic effect for this target population. Finally, the future perspectives of protein supplementation in sports nutrition are discussed. In summary, protein supplementation in sports nutrition is a very promising field of research, whose future perspective lies with the search for alternatives with greater bioactive potential and more sustainable than conventional sources.

Antioxidant and alpha-glucosidase enzyme inhibitory properties of hydrolyzed protein and bioactive peptides of quinoa

The quinoa protein is gaining global attraction due to high content of gluten-free protein. It is a rich source of high-quality protein with all essential amino acids. The objective of this study was to evaluate the antioxidant activity and alpha-glucosidase inhibition effect of bioactive peptides obtained from quinoa protein that was hydrolyzed by alcalase and trypsin. Peptides were fractionated using ultrafiltration with MW cut-off = 3, 10 kDa. The peptide concentration was evaluated using OPA solution and peptide bonds were studied by SDS-PAGE. The highest antioxidant activity obtained from quinoa bioactive peptides by alcalase and trypsin was observed after 0.5 h (10 kDa≤) and 4 h (3 kDa≥), respectively. The highest α-glucosidase inhibition activity was observed in peptides with MW 3 kDa ≥ when hydrolyzed by trypsin. The amino acid composition of the most effective samples has been determined. Comparing the results showed that MW and the composition of peptides influenced the studied traits. From the result of this study, it concluded that bioactive peptides obtained from quinoa protein could be used in functional food and supplements formulation.

Novel Antioxidant Collagen Peptides of Siberian Sturgeon (Acipenser baerii) Cartilages: The Preparation, Characterization, and Cytoprotection of H2O2-Damaged Human Umbilical Vein Endothelial Cells (HUVECs)

For making full use of aquatic by-products to produce high value-added products, Siberian sturgeon (Acipenser baerii) cartilages were degreased, mineralized, and separately hydrolyzed by five kinds of proteases. The collagen hydrolysate (SCH) generated by Alcalase showed the strongest 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) and hydroxide radical (HO·) scavenging activity. Subsequently, thirteen antioxidant peptides (SCP1-SCP3) were isolated from SCH, and they were identified as GPTGED, GEPGEQ, GPEGPAG, VPPQD, GLEDHA, GDRGAEG, PRGFRGPV, GEYGFE, GFIGFNG, PSVSLT, IELFPGLP, LRGEAGL, and RGEPGL with molecular weights of 574.55, 615.60, 583.60, 554.60, 640.64, 660.64, 885.04, 700.70, 710.79, 602.67, 942.12, 714.82, and 627.70 Da, respectively. GEYGFE, PSVSLT, and IELFPGLP showed the highest scavenging activity on DPPH· (EC₅₀: 1.27, 1.05, and 1.38 mg/mL, respectively) and HO· (EC₅₀: 1.16, 0.97, and 1.63 mg/mL, respectively), inhibiting capability of lipid peroxidation, and protective functions on H₂O₂-damaged plasmid DNA. More importantly, GEYGFE, PSVSLT, and IELFPGLP displayed significant cytoprotection on HUVECs against H₂O₂ injury by regulating the endogenous antioxidant enzymes of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to decrease the contents of reactive oxygen species (ROS) and malondialdehyde (MDA). Therefore, the research provided better technical assistance for a higher-value utilization of Siberian sturgeon cartilages and the thirteen isolated peptides—especially GEYGFE, PSVSLT, and IELFPGLP—which may serve as antioxidant additives for generating health-prone products to treat chronic diseases caused by oxidative stress.

Antioxidant Peptides From Protein Hydrolysate of Marine Red Algae Eucheuma cottonii: Preparation, Identification, and Cytoprotective Mechanisms on H2O2 Oxidative Damaged HUVECs

To screen, prepare, identify, and evaluate the activities of natural antioxidants for treating chronic diseases caused by oxidative stress. Two algal proteins, namely ZD10 and ZD60, precipitated with 10 and 60% (NH₄)₂SO₄ were extracted from red algae Eucheuma cottonii (E. cottonii) and hydrolyzed using five proteolytic enzymes. The results showed that ZD60 played the most significant role in the enhancement of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH⋅) scavenging activity (25.91 ± 0.24%) among all protein hydrolysates. Subsequently, six antioxidant peptides (EP1-EP6) were isolated from the papain hydrolysate of ZD60 by ultrafiltration and chromatography methods. Their amino acid sequences were identified as Thr-Ala (EP1), Met-Asn (EP2), Tyr-Ser-Lys-Thr (EP3), Tyr-Ala-Val-Thr (EP4), Tyr-Leu-Leu (EP5), and Phe-Tyr-Lys-Ala (EP6) with molecular weights of 190.21, 263.33, 497.55, 452.51, 407.51, and 527.62 Da, respectively. Of which, EP3, EP4, EP5, and EP6 showed strong scavenging activities on DPPH⋅, hydroxyl radical (HO⋅), and superoxide anion radical (O- 2⋅). Moreover, EP4 and EP5 could significantly protect human umbilical vein endothelial cells (HUVECs) from H₂O₂-induced oxidative damage by increasing the levels of antioxidant enzyme systems including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to reduce the levels of reactive oxygen species (ROS) (60.51 and 51.74% of model group) and malondialdehyde (MDA) (75.36 and 64.45% of model group). In addition, EP4 and EP5 could effectively inhibit H₂O₂-induced apoptosis by preventing HUVECs from early apoptosis to late apoptosis. These results indicated that the antioxidant peptides derived from E. cottonii, especially EP4 and EP5, could serve as the natural antioxidants applied in pharmaceutical products to treat chronic cardiovascular diseases caused by oxidative damage, such as coronary heart disease, atherosclerosis, etc.

Anti-fatigue effects of fermented soybean protein peptides in mice

BACKGROUND

Bioactive protein hydrolysates and peptides are believed to help counteract and ameliorate physical fatigue. Fermented soybean protein peptides (FSPPs) were prepared by protease hydrolysis and microbial fermentation. The present study aimed to evaluate the anti-fatigue properties of FSPPs.

RESULTS

The forced swimming time in the FSPP group was 35.78% longer than the control group, the oxygen-resistant survival time of the FSPP group was significantly prolonged and the prolongation rate was 31.00%. In addition, FSPPs decreased the lactic acid (LD), blood urea nitrogen (BUN) and creatine kinase (CK) concentration by 27.47%, 25.93% and 21.70%, respectively, after treatment, while increasing the levels of liver glycogen and muscle glycogen by 93.35% and 67.31%, respectively. FSPPs can significantly increase gut microbiota diversity and regulate the species richness of gut microbiota. The results of real-time polymerase chain reaction (RT-PCR) and western blotting showed that FSPPs activate p-AMPK/PGC1-α and PI3K/Akt/mTOR signaling pathways.

CONCLUSION

These results indicate that treatment with FSPPs induces anti-fatigue effects, which may be due to the mediating muscle protein synthesis and participation in skeletal muscle hypertrophy, providing energy for muscle cells. FSPPs may have potential applications in the food industry as functional material additives. © 2021 Society of Chemical Industry.

Preventive effect of swim bladder hydrolysates on cyclophosphamide-induced ovarian injury in mice

AIMS

This study aimed to prepare swim bladder hydrolysate (SBH) with M_n  < 4000 Da, and investigate its effects on cyclophosphamide (CTX)-mediated ovarian injury in mice.

METHODS

Hydrolysates were prepared by heating extraction, enzymatic hydrolysis and ultrafiltration. M_n and distribution of SBH were analyzed via gel filtration chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Changes in the mouse oestrus cycle were determined by cytological examination. The number of follicles was examined using histopathology. Enzyme-linked immunosorbent assays (ELISAs) were used to determine the serum sex hormone levels.

RESULTS

The M_n of SBH, prepared by heating extraction, enzymatic hydrolysis, ultrafiltration, and from different batches, was below 4000 Da, and the preparation process was stable. Compared with the control group, the low-, middle-, and high-dose SBH treatment groups showed different trends in oestrus duration, serum sex hormone levels, and the number of primordial and secondary follicles. The oestrus cycle duration of the high-dose SBH group was longer than that of the model group. The serum luteinizing hormone, follicle-stimulating hormone, and anti-Müllerian hormone levels in the middle-dose group were the closest to those of control group. The number of primordial and secondary follicles in the medium-dose group was significantly higher than that in the model group and closest to those of control group.

CONCLUSION

After heating extraction, trypsin/Flavourzyme hydrolysis and ultrafiltration, a hydrolysate with M_n below 4000 Da could be prepared. We found that a moderate (400 mg/kg) SBH dose resulted in the greatest effect on ovarian injury remission in mice.

Antioxidant Mechanisms of the Oligopeptides (FWKVV and FMPLH) from Muscle Hydrolysate of Miiuy Croaker against Oxidative Damage of HUVECs

In this work, the antioxidant mechanisms of bioactive oligopeptides (FWKVV and FMPLH) from protein hydrolysate of miiuy croaker muscle against H₂O₂-damaged human umbilical vein endothelial cells (HUVECs) were researched systemically. The finding demonstrated that the HUVEC viability treated with ten antioxidant peptides (M1 to M10) at 100.0 μM for 24 h was not significantly affected compared with that of the normal group (P < 0.05). Furthermore, FWKVV and FMPLH at 100.0 μM could very significantly enhance the viabilities (75.89 ± 1.79% and 70.03 ± 4.37%) of oxidative-damaged HUVECs by H₂O₂ compared with those of the model group (51.66 ± 2.48%) (P < 0.001). The results indicated that FWKVV and FMPLH played their protective functions through increasing the levels of antioxidant enzymes including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreasing the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and nitric oxide (NO) in oxidative-damaged HUVECs in a dose-dependent manner. In addition, the comet assay revealed that FWKVV and FMPLH could dose-dependently protect deoxyribonucleic acid (DNA) from oxidative damage in the HUVEC model. These results suggested that antioxidant pentapeptides (FWKVV and FMPLH) could serve as potential antioxidant additives applied in the food products, pharmaceuticals, and health supplements.

Purification, Identification, Activity Evaluation, and Stability of Antioxidant Peptides from Alcalase Hydrolysate of Antarctic Krill (Euphausia superba) Proteins

For utilizing the largest source of marine proteins, Antarctic krill (Euphausia superba) proteins were defatted and hydrolyzed separately using pepsin, alcalase, papain, trypsin, and netrase, and alcalase hydrolysate (EPAH) showed the highest DPPH radical (DPPH·) and hydroxyl radical (HO·) scavenging activity among five hydrolysates. Using ultrafiltration and chromatography methods, fifteen antioxidant peptides were purified from EPAH and identified as Asn-Gln-Met (NQM), Trp-Phe-Pro-Met (WFPM), Gln-Asn-Pro-Thr (QNPT), Tyr-Met-Asn-Phe (YMNF), Ser-Gly-Pro-Ala (SGPA), Ser-Leu-Pro-Tyr (SLPY), Gln-Tyr-Pro-Pro-Met-Gln-Tyr (QYPPMQY), Glu-Tyr-Glu-Ala (EYEA), Asn-Trp-Asp-Asp-Met-Arg-Ile-Val-Ala-Val (NWDDMRIVAV), Trp-Asp-Asp-Met-Glu-Arg-Leu-Val-Met-Ile (WDDMERLVMI), Asn-Trp-Asp-Asp-Met-Glu-Pro-Ser-Phe (NWD-DMEPSF), Asn-Gly-Pro-Asp-Pro-Arg-Pro-Ser-Gln-Gln (NGPDPRPSQQ), Ala-Phe-Leu-Trp-Asn (AFLWA), Asn-Val-Pro-Asp-Met (NVPDM), and Thr-Phe-Pro-Ile-Tyr-Asp-Tyr-Pro-Gln (TFPIYDPQ), respectively, using a protein sequencer and ESI/MS. Among fifteen antioxidant peptides, SLPY, QYPPMQY and EYEA showed the highest scavenging activities on DPPH· (EC₅₀ values of 1.18 ± 0.036, 1.547 ± 0.150, and 1.372 ± 0.274 mg/mL, respectively), HO· (EC₅₀ values of 0.826 ± 0.027, 1.022 ± 0.058, and 0.946 ± 0.011 mg/mL, respectively), and superoxide anion radical (EC₅₀ values of 0.789 ± 0.079, 0.913 ± 0.007, and 0.793 ± 0.056 mg/mL, respectively). Moreover, SLPY, QYPPMQY and EYEA showed strong reducing power, protective capability against H₂O₂-damaged plasmid DNA, and lipid peroxidation inhibition ability. Furthermore, SLPY, QYPPMQY, and EYEA had high stability under temperatures lower than 80 °C, pH values ranged from 6-8, and simulated GI digestion for 180 min. The results showed that fifteen antioxidant peptides from alcalase hydrolysate of Antarctic krill proteins, especially SLPY, QYPPMQY and EYEA, might serve as effective antioxidant agents applied in food and health products.

Anti-fatigue property of the oyster polypeptide fraction and its effect on gut microbiota in mice

We aimed to evaluate the anti-fatigue effects of the oyster polypeptide (OP) fraction and its regulatory effect on the gut microbiota in mice. Our exhaustive swimming experiment showed that the swimming time of the low-, middle- and high-dose groups of the OP fraction was increased by 1.82, 2.18 and 2.44 times compared with the control group, respectively. Besides, the liver glycogen levels of the three groups were increased by 19.3%, 42.02% and 65.07%, while the lactate levels were decreased by 18.85%, 21.18% and 28.74%, respectively. Moreover, administration of the OP fraction upregulated the expressions of PEPCK and AMPK, but downregulated the TNF-α expression. Correlation analysis between the gut microbiota and fatigue-related biochemical indicators showed that Faecalibacterium, Desulfovibri and Intestinibacter were negatively correlated with the swimming time, blood lactate, blood urea nitrogen, liver glycogen and muscle glycogen, while Yaniella and Romboutsia were positively correlated. Therefore, the OP fraction had anti-fatigue effects, and could regulate the abundance of gut microbiota and maintain its balance.

A novel extraction approach and unique physicochemical properties of gelatin from the swim bladder of sturgeon

BACKGROUND

Gelatin is traditionally produced from mammals and widely applied in the food industry. The production is tedious, time-consuming and environment-unfriendly, while the application is restricted because of zoonosis risk and religious sentiment.

RESULTS

Gelatin was extracted by hot water from sturgeon swim bladder after defatting with alcohol and hexane. The yield reached to 94.15% under the optimized conditions of 50 °C, 30 min and 10 mL g^-1 . Its amino acid and subunit profiles were similar to type I collagen. Compared to commercial porcine, bovine and piscine gelatins, it exhibited higher whiteness (3.38), emulsion activity (171.76 m² g^-1 ), gel strength (853.23 g), water-holding capacity (92.37%) and viscoelasticity (0.03). But the transmittance (40.56% at 450 nm and 59.07% at 620 nm), emulsion stability (30.09 min), foam expansion (203.00) and stability (26.92), gelling (16.88 °C) and melting temperature (21.80 °C) were lower. While the pH (6.87) and viscosity (28.60 mPa s) were moderate. Moreover, it made better hydrogels and nanofibers.

CONCLUSION

Gelatin was extracted from sturgeon swim bladder using a clean and efficient approach, and exhibited unique properties and great potential for the food industry. © 2020 Society of Chemical Industry.

Supplementation with embryo chicken egg extract improves exercise performance and exerts anti-fatigue effects via AMPK/mTOR signalling pathway in mice

BACKGROUND

Embryo chicken egg is a nutritional supplement that has been used to enhance physical fitness and promote wound healing according to traditional Chinese medicine for many years. In this study, we evaluated the effects of embryo chicken egg extract (ECE) on the exercise performance and fatigue in mice and the underlying mechanisms.

RESULTS

The results indicated that ECE can prolong the exhaustive swimming time, decrease lactic acid, blood urea nitrogen, creatine kinase, and malondialdehyde levels, and increase superoxide dismutase, glutathione peroxidase, and glycogen levels. Additionally, ECE can also regulate the balance of oxidative stress via the adenosine monophosphate activated protein kinase/mammalian target of rapamycin signalling pathway.

CONCLUSION

Taken together, these results showed that ECE can improve exercise performance and reduce physical fatigue in mice, which indicates that ECE can be used as a potential supplement to reduce physical fatigue. © 2020 Society of Chemical Industry.

A Review of Bioactive Peptides: Chemical Modification, Structural Characterization and Therapeutic Applications

In recent years, the development and applications of protein drugs have attracted extensive attention from researchers. However, the shortcomings of protein drugs also limit their further development. Therefore, bioactive peptides isolated or simulated from protein polymers have broad application prospects in food, medicine, biotechnology, and other industries. Such peptides have a molecular weight distribution between 180 and 1000 Da. As a small molecule substance, bioactive peptide is usually degraded by various enzymes in the organism and have a short half-life. At the same time, such substances have poor stability and are difficult to produce and store. Therefore, these active peptides may be modified through phosphorylation, glycosylation, and acylation. Compared with other protein drugs, the modified active peptides are more easily absorbed by the body, have longer half-life, stronger targeting, and fewer side effects in addition to higher bioavailability. In the light of their functions, bioactive peptide can be divided into antimicrobial, anti-tumour, anti-angiogenic, antioxidant, anti-fatigue, and anti-hypertensive peptides. This article mainly focuses on the introduction of several promising biologically active peptides functioning as antimicrobial, anti-tumour, antiangiogenic, and antioxidant peptides from the three aspects modification, structural characteristics and mechanism of action.

In vitro antioxidant and antihypertensive properties of sesame seed enzymatic protein hydrolysate and ultrafiltration peptide fractions

The objective of this study was to determine the in vitro antioxidant and antihypertensive potentials of sesame seed protein hydrolysate and its membrane ultrafiltration peptide fractions in comparison to the unhydrolyzed protein. Sesame seed protein isolate (SESPI) was prepared from the defatted sesame seed meal and then hydrolyzed using consecutive additions of pepsin and pancreatin to yield sesame protein hydrolysate (SESPH). The SESPH was subjected to membrane ultrafiltration consecutively to obtain fractions with peptide sizes of <1, 1-3, 3-5, and 5-10 kDa, respectively, which were then assayed for in vitro antioxidant and antihypertensive properties. The results showed that protein hydrolysis and fractionation led to significant (p < .05) increases in the content of hydrophobic amino acids. Radical scavenging and metal ion chelation were also significantly (p < .05) enhanced by these treatments. Inhibition of linoleic acid oxidation was stronger with the 1.0 mg/ml of sesame peptide samples in comparison to the mild inhibitory effect exhibited by the 0.5 mg/ml of samples. The <1 kDa peptide fraction was the most active inhibitor (81%) against angiotensin converting enzyme, whereas the bigger peptides (>3-5 and 5-10 kDa) were the most effective (75%-85% ) inhibitors against renin. These sesame products could be used as therapeutic agents in the development of health enhancing foods for the prevention and management of chronic diseases. PRACTICAL APPLICATIONS: Bioactive peptides have been produced from plant protein sources through in vitro enzymatic activities. Sesame seed peptides have demonstrated multifunctional potential to act as antioxidative and antihypertensive agents that could be utilized as ingredients for the development of novel functional foods and nutraceuticals.

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.

The anti-skin-aging effect of oral administration of gelatin from the swim bladder of Amur sturgeon (Acipenser schrenckii)

Gelatin was extracted from the swim bladder of Amur sturgeon with hot water at 50 °C with acceptable yield (76.54%) and it showed type I collagen features. The degree of hydrolysis reached 70.42%, and 26.55% of collagen peptides (380.76 Da) survived, after simulating digestion, absorption and peripheral blood circulation in vitro. In situ single-pass intestinal perfusion showed that the AMW of the collagen peptides was about 1100 Da in the intestine and they were mainly absorbed in the jejunum (61.11%). A 12-month feeding experiment using rats demonstrated that gelatin improved the histological structure, increased the thickness of the dermis (18.45%) and the density of collagen fibers (22.17%), and decreased the ratio of type III to type I collagen (43.44%) of chronologically aged skin at 3.85 g per kg bw per d. Moreover, the antioxidant enzyme activities in skin were significantly enhanced, while the malondialdehyde content was reduced by 31.99%. These results provided new insights into the development of new nutraceuticals and functional foods for the anti-skin-aging effect.

Cytoprotective Effect of Antioxidant Pentapeptides from the Protein Hydrolysate of Swim Bladders of Miiuy Croaker (Miichthys miiuy) against H2O2-Mediated Human Umbilical Vein Endothelial Cell (HUVEC) Injury

In our previous research, ten antioxidant pentapeptides including FYKWP, FTGMD, GFEPY, YLPYA, FPPYERRQ, GFYAA, FSGLR, FPYLRH, VPDDD, and GIEWA were identified from the hydrolysate of miiuy croaker (Miichthys miiuy) swim bladder. In this work, their protective function on H₂O₂-induced oxidative damage to human umbilical vein endothelial cells (HUVECs) was studied. Results indicated that there was no significant difference in the HUVEC viability between the normal group and the treated groups with the 10 pentapeptides at the concentration of 100 μM for 24 h (p < 0.05). Furthermore, FPYLRH of 100 μg/mL extremely significantly (p < 0.001) increased the viability (80.58% ± 5.01%) of HUVECs with H₂O₂-induced oxidative damage compared with that of the model group. The protective mechanism indicated that FPYLRH could extremely significantly (p < 0.001) increase the levels of superoxide dismutase (SOD) (211.36 ± 8.29 U/mg prot) and GSH-Px (53.06 ± 2.34 U/mg prot) and decrease the contents of reactive oxygen species (ROS) (139.1 ± 11.8% of control), malondialdehyde (MDA) (13.66 ± 0.71 nM/mg), and nitric oxide (NO) (4.36 ± 0.32 µM/L) at the concentration of 100 μM in HUVECs with H₂O₂-induced oxidative damage compared with those of the model group. In addition, FPYLRH dose-dependently protected DNA in oxidative damage HUVECs model. These results suggested that FPYLRH could significantly attenuate the H₂O₂-induced stress injury in HUVECs and might be used as a potential natural antioxidant in the functional food industries.

Antioxidant Peptides from the Protein Hydrolysate of Spanish Mackerel (Scomberomorous niphonius) Muscle by in Vitro Gastrointestinal Digestion and Their In Vitro Activities

For the full use of Spanish mackerel (Scomberomorous niphonius) muscle to produce antioxidant peptides, the proteins of Spanish mackerel muscle were separately hydrolyzed under five kinds of enzymes and in vitro gastrointestinal digestion, and antioxidant peptides were isolated from the protein hydrolysate using ultrafiltration and multiple chromatography methods. The results showed that the hydrolysate (SMPH) prepared using in vitro GI digestion showed the highest degree of hydrolysis (27.45 ± 1.76%) and DPPH radical scavenging activity (52.58 ± 2.68%) at the concentration of 10 mg protein/mL among the six protein hydrolysates, and 12 peptides (SMP-1 to SMP-12) were prepared from SMPH. Among them, SMP-3, SMP-7, SMP-10, and SMP-11 showed the higher DPPH radical scavenging activities and were identified as Pro-Glu-Leu-Asp-Trp (PELDW), Trp-Pro-Asp-His-Trp (WPDHW), and Phe-Gly-Tyr-Asp-Trp-Trp (FGYDWW), and Tyr-Leu-His-Phe-Trp (YLHFW), respectively. PELDW, WPDHW, FGYDWW, and YLHFW showed high scavenging activities on DPPH radical (EC₅₀ 1.53, 0.70, 0.53, and 0.97 mg/mL, respectively), hydroxyl radical (EC₅₀ 1.12, 0.38, 0.26, and 0.67 mg/mL, respectively), and superoxide anion radical (EC₅₀ 0.85, 0.49, 0.34, and 1.37 mg/mL, respectively). Moreover, PELDW, WPDHW, FGYDWW, and YLHFW could dose-dependently inhibit lipid peroxidation in the linoleic acid model system and protect plasmid DNA (pBR322DNA) against oxidative damage induced by H₂O₂ in the tested model systems. In addition, PELDW, WPDHW, FGYDWW, and YLHFW could retain their high activities when they were treated under a low temperature (<60 °C) and a moderate pH environment (pH 5–9). These present results indicate that the protein hydrolysate, fractions, and isolated peptides from Spanish mackerel muscle have strong antioxidant activity and might have the potential to be used in health food products.

Four Antioxidant Peptides from Protein Hydrolysate of Red Stingray (Dasyatis akajei) Cartilages: Isolation, Identification, and In Vitro Activity Evaluation

In the work, water-soluble proteins of red stingray (Dasyatis akajei) cartilages were extracted by guanidine hydrochloride and hydrolyzed using trypsin. Subsequently, four antioxidant peptides (RSHP-A, RSHP-B, RSHP-C, and RSHP-D) were isolated from the water-soluble protein hydrolysate while using ultrafiltration and chromatographic techniques, and the amino acid sequences of RSHP-A, RSHP-B, RSHP-C, and RSHP-D were identified as Val-Pro-Arg (VPR), Ile-Glu-Pro-His (IEPH), Leu-Glu-Glu--Glu-Glu (LEEEE), and Ile-Glu-Glu-Glu-Gln (IEEEQ), with molecular weights of 370.46 Da, 494.55 Da, 647.64 Da, and 646.66 Da, respectively. VPR, IEPH, LEEEE, and IEEEQ exhibited good scavenging activities on the DPPH radical (EC50 values of 4.61, 1.90, 3.69, and 4.01 mg/mL, respectively), hydroxyl radical (EC50 values of 0.77, 0.46, 0.70, and 1.30 mg/mL, respectively), superoxide anion radical (EC50 values of 0.08, 0.17, 0.15, and 0.16 mg/mL, respectively), and ABTS cation radical (EC50 values of 0.15, 0.11, 0.19, and 0.18 mg/mL, respectively). Among the four isolated antioxidant peptides, IEPH showed the strongest reducing power and lipid peroxidation inhibition activity, but LEEEE showed the highest Fe2+-chelating ability. The present results suggested that VPR, IEPH, LEEEE, and IEEEQ might have the possibility of being an antioxidant additive that is used in functional food and pharmaceuticals.

Purification and Characterization of Antioxidant Peptides Derived from Protein Hydrolysate of the Marine Bivalve Mollusk Tergillarca granosa

In this report, protein hydrolysate (TGH) of blood cockle (Tegillarca granosa) was prepared using a two-enzyme system (Alcalase treatment for 1.5 h following Neutrase treatment for 1.5 h). Subsequently, six antioxidant peptides were isolated from TGH using ultrafiltration and chromatography methods, and their amino acid sequences were identified as EPLSD, WLDPDG, MDLFTE, WPPD, EPVV, and CYIE with molecular weights of 559.55, 701.69, 754.81, 513.50, 442.48, and 526.57 Da, respectively. In which, MDLFTE and WPPD exhibited strong scavenging activities on DPPH radical (EC50 values of 0.53 ± 0.02 and 0.36 ± 0.02 mg/mL, respectively), hydroxy radical (EC50 values of 0.47 ± 0.03 and 0.38 ± 0.04 mg/mL, respectively), superoxide anion radical (EC50 values of 0.75 ± 0.04 and 0.46 ± 0.05 mg/mL, respectively), and ABTS cation radical (EC50 values of 0.96 ± 0.08 and 0.54 ± 0.03 mg/mL, respectively). Moreover, MDLFTE and WPPD showed high inhibiting ability on lipid peroxidation. However, MDLFTE and WPPD were unstable and could not retain strong antioxidant activity at high temperatures (>80 °C for 0.5 h), basic pH conditions (pH > 9 for 2.5 h), or during simulated GI digestion. In addition, the effect of simulated gastrointestinal digestion on TGP4 was significantly weaker than that on MDLFTE. Therefore, MDLFTE and WPPD may be more suitable for serving as nutraceutical candidates in isolated forms than as food ingredient candidates in functional foods and products.

Eight Collagen Peptides from Hydrolysate Fraction of Spanish Mackerel Skins: Isolation, Identification, and In Vitro Antioxidant Activity Evaluation

A previous report indicated that collagen hydrolysate fraction (F7) from Spanish mackerel (Scomberomorous niphonius) skins showed high reducing power and radical scavenging activities on 2,2-Diphenyl-1-picrylhydrazyl (DPPH) (EC50 value of 1.57 mg/mL) and hydroxyl (EC50 value of 1.20 mg/mL). In this work, eight peptides were isolated from F7 and identified as Gly-Pro-Tyr (GPY, 335.31 Da), Gly-Pro-Thr-Gly-Glu (GPTGE, 459.47 Da), Pro-Phe-Gly-Pro-Asp (PFGPD, 531.52 Da), Gly-Pro-Thr-Gly-Ala-Lys (GPTGAKG, 586.65 Da), Pro-Tyr-Gly-Ala-Lys-Gly (PYGAKG, 591.69 Da), Gly-Ala-Thr-Gly-Pro-Gln-Gly (GATGPQG, 586.61 Da), Gly-Pro-Phe-Gly-Pro-Met (GPFGPM, 604.73 Da), and Tyr-Gly-Pro-Met (YGPM, 466.50 Da), respectively. Among them, PFGPD, PYGAKG, and YGPM exhibited strong radical scavenging activities on DPPH (EC50 values of 0.80, 3.02, and 0.72 mg/mL for PFGPD, PYGAKG, and YGPM, respectively), hydroxyl (EC50 values of 0.81, 0.66, and 0.88 mg/mL for PFGPD, PYGAKG, and YGPM, respectively), superoxide anion (EC50 values of 0.91, 0.80, and 0.73 mg/mL for PFGPD, PYGAKG, and YGPM, respectively), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) cation (EC50 values of 0.86, 1.07, and 0.82 mg/mL for PFGPD, PYGAKG, and YGPM, respectively) in a positive concentration-activity relationship. Furthermore, PFGPD, PYGAKG, and YGPM could effectively reduce Fe3+ to Fe2+ and inhibit lipid peroxidation. Hence, eight collagen peptides from hydrolysate of Spanish mackerel skins might be served as antioxidant candidates for various industrial applications.

Anti-fatigue and anti-oxidant activities of oyster (Ostrea rivularis) hydrolysate prepared by compound protease

Oyster, which is rich in protein and widely used as a marine traditional Chinese medicine, was believed to have good curative effects in health care and on chronic diseases. This study was designed to evaluate the anti-fatigue and anti-oxidant effects of oyster hydrolysate. Oyster meat (OM) was hydrolyzed with a complex protease, and oyster hydrolysate (OH) was separated by a 6 kDa ultrafiltration membrane into two fractions, OH-I (<6 kDa) and OH-II (≥6 kDa). The anti-fatigue effects of OM, OH, OH-I and OH-II groups were first investigated, and then the antioxidant activities of OH-I and OH-II were further analyzed. Anti-fatigue experimental results showed that OH-I displayed the strongest activity among the four groups. Compared to the control group, OH-I significantly prolonged swimming time (67.79%), increased the content of muscle glycogen (45.65%) and liver glycogen (49.01%), and reduced the content of blood urea nitrogen (BUN) (18.44%) (P < 0.05). Meanwhile, OH-I showed excellent chemical and cellular antioxidant activities, especially when the concentration increased; its antioxidant activity was significantly better than that of OH-II (P < 0.05). Results of an amino acid analysis showed that OH-I was rich in branched-chain amino acids (10.84 g per 100 g), Glu (8.63 g per 100 g), Tau (1.68 g per 100 g), Asp (5.02 g per 100 g) and Arg (3.61 g per 100 g), which were expected to contribute to its antioxidant and anti-fatigue activities.

High Fischer ratio oligopeptides determination from Antartic krill: Preparation, peptides profiles, and in vitro antioxidant activity

In this work, alcalase and flavorzyme were chosen as the hydrolase for preparing high Fischer ratio oligopeptides from Antarctic krill (Euphausia superba) (HFP) using sequential enzyme hydrolysis process, and their hydrolysis conditions were optimized using single factor experiment. According to the Fischer ratio, granular activated carbon of XHJ-200 (200 mesh) showed the best way to remove aromatic amino acids and its optimal parameters were pH value of 6.0, adsorption time of 2.5 hr, temperature of 25°C, and solid-liquid ratio of 1:20. The Fischer ratio and average molecular weight of HFP were 21.12 (>20) and 779.9 Da, respectively. In addition, the peptide profile of HFP was established using RP-HPLC and 23 oligopeptides isolated from HFP including 6 dipeptides, 9 tripeptides, 3 tetrapeptides, and 5 pentapeptides were identified using protein amino acid sequence analyzer and mass spectrum. Furthermore, HFP exhibited high radical scavenging activity, reducing power, and lipid peroxidation inhibition capability. PRACTICAL APPLICATIONS: High Fischer ratio oligopeptides (HFO) is a kind of small peptide mixture with the mole ratio of branched-chain amino acids (BCAA) to aromatic amino acids (AAA) higher than 20, which has drawn a great attention due to its great potential in clinical nutrition approaches for the treatment of liver disease when amino acid composition is out of proportion characterized by low levels of BCAA and high levels of AAA in the systemic blood. Antarctic krill is regarded as the largest animal protein resource for various food and pharmaceutical products. However, there is no report on the preparation of HFO of Antarctic krill (HFP). Therefore, the aim of the present study was to investigate the preparation process, peptide profiles and in vitro antioxidant activity of HFP. This study will potentially enhance the value-added utilization of Antarctic krill by making it an important raw material in the health-promoting functional products.

Purification and Characterization of a Novel Pentadecapeptide from Protein Hydrolysates of Cyclina sinensis and Its Immunomodulatory Effects on RAW264.7 Cells

In the present study, peptide fractions of Cyclina sinensis hydrolysates, with molecular weight (MW) < 3 kDa and highest relative proliferation rate of murine macrophage cell line RAW 264.7, were purified by a series of chromatographic purification methods, to obtain peptide fractions with immunomodulatory activity. The amino acid sequence of the peptide was identified to be Arg-Val-Ala-Pro-Glu-Glu-His-Pro-Val-Glu-Gly-Arg-Tyr-Leu-Val (RVAPEEHPVEGRYLV) with MW of 1750.81 Da, and the novel pentadecapeptide (named SCSP) was synthesized for subsequent immunomodulatory activity experiments. Results showed the SCSP enhanced macrophage phagocytosis, increased productions of nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), and up-regulated the protein level of inducible nitric oxide synthase (iNOS), nuclear factor κB (NF-κB), and NOD-like receptor protein 3 (NLRP3) in RAW 264.7 cells. Furthermore, the expression of inhibitor of nuclear factor κB-α (IκB-α) was down-regulated. These findings suggest that SCSP might stimulate macrophage activities by activating the NF-κB signaling pathway and can be used as a potential immunomodulatory agent in functional food or medicine.

Small Molecule Oligopeptides Isolated from Walnut (Juglans regia L.) and Their Anti-Fatigue Effects in Mice

Walnut (Juglans regia L.) is unique for its extensive biological activities and pharmaceutical properties. There are few studies on walnut oligopeptides (WOPs), which are small molecule peptides extracted from walnuts. This study aimed to evaluate the anti-fatigue effects of WOPs on ICR mice and explore the possible underlying mechanism. Mice were randomly divided into four experimental sets and each set of mice were then randomly divided into four groups. The vehicle group was administered distilled water, and the three WOP intervention groups were orally administered WOP solution at a dose of 110, 220, and 440 mg/kg of body weight, respectively. After 30 days of WOP intervention, the anti-fatigue activity of WOPs were evaluated using the weight-loaded swimming test and by measuring the change of biochemical parameters, glycogen storage and energy metabolism enzymes, anti-oxidative capacity and mitochondrial function. It was observed that WOPs could significantly prolong the swimming time, decrease the accumulation of lactate dehydrogenase (LDH), creatine kinase (CK), blood urea nitrogen (BUN) and blood lactic acid (BLA), and increased the glycogen storage of liver and gastrocnemius muscle. WOPs also markedly inhibited fatigue induced oxidative stress by increasing the activity of superoxide dismutase (SOD), glutathione peroxidase (GPX) and decreasing the content malondialdehyde (MDA). Notably, WOPs improved the activity of pyruvate kinase (PK), succinate dehydrogenase (SDH), Na+-K+-ATPase, and enhanced the mRNA expression of mitochondrial biogenesis factors and mitochondrial DNA content in skeletal muscles of mice. These results suggest that WOPs have beneficial anti-fatigue effects, which may be attributed to their positive effects on increasing glycogen storage, improving energy metabolism, inhibiting oxidative stress, enhancing mitochondrial function in skeletal muscle, and ameliorating the cell damage and the muscular injury.

A novel anti‑proliferative pentapeptide (ILYMP) isolated from Cyclina sinensis protein hydrolysate induces apoptosis of DU‑145 prostate cancer cells

Prostate cancer is the main causes of cancer associated mortality in men worldwide, cancer patients often suffer serious side effects when treated with chemotherapy or radiotherapy, therefore novel drugs are in high demand to treat prostate cancer. In the present study, a pentapeptide (Ile‑Leu‑Tyr‑Met‑Pro; ILYMP) with a molecular weight of 635.71 Da was isolated from the protein hydrolysate of Cyclina sinensis via ultrafiltration and chromatographic methods, and subsequently named Cyclina sinensis pentapeptide (CSP). The activity of CSP was first investigated in prostate cancer (PCa) DU‑145 cells. CSP was demonstrated to significantly inhibit DU‑145 cell proliferation at a half‑maximal inhibitory concentration of 11.25 mM at a 72 h time interval. In addition, the results of acridine orange/ethidium bromide double staining, scanning electron microscopy and flow cytometry analyses suggested that CSP inhibited DU‑145 cell proliferation via the induction of apoptosis. Following treatment with CSP, Bcl‑2‑associated X (Bax), cleaved caspase‑3 and cleaved caspase‑9 protein expression levels were enhanced in DU‑145 cells; whereas B‑cell lymphoma 2 expression was suppressed in DU‑145 cells. In conclusion, to the best of the authors' knowledge, this is the first study to investigate the effects of an anti‑proliferative peptide derived from Cyclina sinensis on DU‑145 cells, and the results suggested that CSP may represent a therapeutic nutraceutical agent for the treatment of patients with PCa.

Bioactive Peptides from Cartilage Protein Hydrolysate of Spotless Smoothhound and Their Antioxidant Activity In Vitro

In the experiment, crude proteins from spotless smoothhound (Mustelus griseus), cartilages were isolated by HCl-Guanidine buffer, and its hydrolysate was prepared using trypsin at pH 8.0, 40 °C with a total enzyme dose of 2.5%. Subsequently, three antioxidant peptides were purified from the hydrolysate using membrane ultrafiltration, anion-exchange chromatography, gel filtration chromatography, and reverse phase high-performance liquid chromatography. The amino acid sequences of isolated peptides were identified as Gly-Ala-Glu-Arg-Pro (MCPE-A); Gly-Glu-Arg-Glu-Ala-Asn-Val-Met (MCPE-B); and Ala-Glu-Val-Gly (MCPE-C) with molecular weights of 528.57, 905.00, and 374.40 Da, respectively, using protein amino acid sequence analyzer and mass spectrum. MCPE-A, MCPE-B and MCPE-C exhibited good scavenging activities on 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH•) (EC₅₀ 3.73, 1.87, and 2.30 mg/mL, respectively), hydroxyl radicals (HO•) (EC₅₀ 0.25, 0.34, and 0.06 mg/mL, respectively), 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radicals (ABTS⁺•) (EC₅₀ 0.10, 0.05, and 0.07 mg/mL, respectively) and superoxide anion radicals (O2−•) (EC₅₀ 0.09, 0.33, and 0.18 mg/mL, respectively). MCPE-B showed similar inhibiting ability on lipid peroxidation with butylated hydroxytoluene (BHT) in a linoleic acid model system. Furthermore, MCPE-A, MCPE-B, and MCPE-C could protect H₂O₂-induced HepG2 cells from oxidative stress by decreasing the content of malonaldehyde (MDA) and increasing the levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione reductase (GSH-Rx). Glu, Gly, Met, and Pro in their sequences and low molecular weight could be attributed to the antioxidant activities of three isolated peptides. These results suggested that GAERP (MCPE-A), GEREANVM (MCPE-B), and AEVG (MCPE-C) from cartilage protein hydrolysate of spotless smoothhound might serve as potential antioxidants and be used in the pharmaceutical and health food industries.

The anti-fatigue activities of Tuber melanosporum in a mouse model

Tuber melanosporum (TM) is an edible fungus that exhibits antioxidant and anti-tumor activity via its unique bioactive metabolites. The present study analyzed the anti-fatigue effects of TM using a BALB/c mouse model. The anti-fatigue properties of TM were evaluated by assessing the endurance of mice by performing forced swimming, rotary rod and running tests. Following 2 weeks TM treatment, hepatic and muscular ATP, and glycogen levels were increased in mice subjected to 30 min swimming, compared with controls. Similarly, levels of serum lactic acid and lactic dehydrogenase were decreased in the same group, compared with the control. Additionally, TM treatment reduced reactive oxygen species and malondialdehyde levels, and increased superoxide dismutase and glutathione peroxidase levels in the muscle, liver and/or serum. The effect of TM on hormone levels was also investigated in the present study, as different efficacies of TM were observed in male and female mice. TM treatment increased serum levels of progesterone, estradiol and testosterone in female and male mice, whereas a decrease in serum luteinizing hormone levels was only observed in females. A decrease in serum follicle-stimulating hormone levels was identified in females, whereas an increase was observed in males. The current study demonstrated that the anti-fatigue effects of TM occur via the regulation of oxidative stress, energy metabolism and hormone levels.

Optimization of Extraction Conditions and Characterization of Pepsin-Solubilised Collagen from Skin of Giant Croaker (Nibea japonica)

In the present study, response surface methodology was performed to investigate the effects of extraction parameters on pepsin-solubilised collagen (PSC) from the skin of the giant croaker Nibea japonica. The optimum extraction conditions of PSC were as follows: concentration of pepsin was 1389 U/g, solid-liquid ratio was 1:57 and hydrolysis time was 8.67 h. Under these conditions, the extraction yield of PSC was up to 84.85%, which is well agreement with the predict value of 85.03%. The PSC from Nibea japonica skin was then characterized as type I collagen by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The fourier transforms infrared spetroscopy (FTIR) analysis revealed that PSC maintains its triple-helical structure by the hydrogen bond. All PSCs were soluble in the pH range of 1.0-4.0 and decreases in solubility were observed at neutral or alkaline conditions. All PSCs had a decrease in solubility in the presence of sodium chloride, especially with a concentration above 2%. So, the Nibea japonica skin could serve as another potential source of collagen.