Antioxidant Peptide Isolated from Muscle Protein of Bullfrog, Rana catesbeiana Shaw

The Role of Amphibian AMPs Against Oxidative Stress and Related Diseases

Amphibians use their skin as an effective defense mechanism against predators and microorganisms. Specialized glands produce antimicrobial peptides (AMPs) that possess antioxidant properties, effectively reducing reactive oxygen species (ROS) levels. These peptides are promising candidates for treating diseases associated with oxidative stress (OS) and redox imbalance, including neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), as well as age-related conditions, like cardiovascular diseases and cancer. This review highlights the multifaceted roles of AMPs and antioxidant peptides (AOPs) in amphibians, emphasizing their protective capabilities against oxidative damage. They scavenge ROS, activate antioxidant enzyme systems, and inhibit cellular damage. AOPs often share structural characteristics with AMPs, suggesting a potential evolutionary connection and similar biosynthetic pathways. Peptides such as brevinin-1FL and Cath-KP demonstrate neuroprotective effects, indicating their therapeutic potential in managing oxidative stress-related diseases. The antioxidant properties of amphibian-derived peptides pave the way for novel therapeutic developments. However, a deeper understanding of the molecular mechanisms underlying these peptides and their interactions with oxidative stress is essential to addressing ROS-related diseases and advancing therapeutic strategies in clinical practice.

A review: Interactions between protein from blue foods and functional components in delivery systems: Function exertion and transmembrane transport by in vitro digestion/cells model

Functional compounds (FCs) had some functions, which are affected easily by digestion and transmembrane transport leading to low absorption rates, such as lutein, quercetin, xylo-oligosaccharide. Protein from blue foods is a potential bioactive compound, which had higher bioavailability, especially for bioactive peptides (BBPs). The BBPs has great limitations, especially the variability under pepsin digestion. However, the limitation of single FCs and BBPs in bioavailability might can be complemented by mixture of different bioactive compounds. Therefore, this review provides an in-depth study on the function and mechanism of different FCs/BBPs and their mixtures. Specifically, digestion effect of mixtures on function and transmembrane transport mechanisms of different bioactive compounds were exhibited to elaborate interactions between BBPs and FCs in delivery systems (function and bioavailability). Combination of FCs/BBPs could enhance bioactive compounds function by mutual complement of function mechanisms, as well as improving the function after digestion by regulating digestion process. Moreover, transmembrane absorption and transport of FCs/BBPs also could be facilitated by mixtures due to complement of transmembrane mechanism (endocytosis, protein channels, cell bypass way). This manuscript lays a foundation for the development of active ingredient bioavailability in functional food processing.

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.

Sea Bass Side Streams Extracts Obtained by Pulsed Electric Fields: Nutritional Characterization and Effect on SH-SY5Y Cells

Fish side streams are an environmental and economic problem. In this work, pulsed electric fields (PEF) extraction was optimized and used as a new method for their valorization. Sea bass head, skin, viscera, and backbone were used. PEF technology (123-300 kJ/kg, 1-3 kV/cm) improved the extraction of proteins and antioxidant compounds from head and skin, but was not successful for viscera. SDS-PAGE showed that the protein molecular weight distribution was affected by the extraction process, revealing differences between the control and PEF extraction conditions. In addition, the extraction of macro-minerals and micro-minerals were also evaluated. The effect of PEF differed according to the matrix and the mineral studied. Heavy metals were also taken into account, studying the presence of As, Cd, Hg, and Pb in the extracts. PEF pre-treatment reduced the presence of As in skin, viscera, and backbone, ranging from 18.25 to 28.48% according to the matrix evaluated. The analysis of potential antioxidant bioactive peptides showed that the treatment of the sample directly influenced their variety. Additionally, the extracts obtained from the head were found to increase cell viability when tested on SH-SY5Y cells. In conclusion, PEF extraction can be a useful tool for the valorization of fish side streams.

Identification of a novel hypotensive peptide from porcine plasma hydrolysate by in vitro digestion and rat model

•

Porcine plasma was enzymatically hydrolyzed with different times.

•

The hydrolysate with high hydrolysis degree was isolated and purified by G-15 gel chromatography and HPLC.

•

The ace inhibition rates of different purified compounds were determined.

•

The sequence of the polypeptide with best ace inhibition (IFPPKPKDTL) was determined by Q exactive LC-MS / MS.

•

The hypotensive function of synthetic peptide IFPPKPKDTL was also determined in spontaneously hypertensive rat.

We separated a novel functional peptide IFPPKPKDTL from porcine plasma hydrolysate by chromatography, HPLC, and identified by Q Exactive LC-MS/MS. Results showed that IFPPKPKDTL had a significant ability of ACE inhibition (76.6%) likely due to the presence of hydrophobic, aromatic, and acidic amino acids that can inactivate ACE by binding Zn²⁺, providing a hydrogen atom to maintain the link between ACE and the peptide. Furthermore, the ACE inhibition of synthetic IFPPKPKDTL was improved by 15.6% after in vitro digestion. Additionally, the systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rats gavaged by the peptide (30 mg/kg). Thereby, ACE inhibitory peptide IFPPKPKDTL from porcine plasma was stable and has potential functional value.

Identification of novel antioxidant peptide from porcine plasma hydrolysate and its effect in in vitro digestion/HepG2 cells model

A novel antioxidant peptide EDEQKFWGK from porcine plasma hydrolysate (PPH) was separated by chromatography, HPLC, and identified by LC-MS/MS. Results showed that EDEQKFWGK had better antioxidant ability (Hydroxyl RAS 32.19%, ABTS RAS 92.93% and DPPH RAS 26.76%) compared with glutathione (30.11%, 82.01%, 26.44%) due to the presence of hydrophobic, aromatic acids (F, W) and acidic amino acids (E, D), decreasing ROS by providing hydrogen atom and chelating metal ions. Furthermore, the antioxidant properties of synthetic EDEQKFWGK still significant despite in vitro digestion because of the production of smaller active peptide. Additionally, it could increase SOD, CAT, GSH-Px to resist oxidative damage in HepG2 cells by inhibiting ROS (O₂ ^- , OH·), forming complexes to prevent OH· from destroying DNA and binding to ARE to promote antioxidase expression. Thereby, the novel peptide EDEQKFWGK from porcine plasma had much stable antioxidant properties and hade great potential in formulating functional foods. PRACTICAL APPLICATIONS: This research isolated a novel antioxidant peptide. Moreover, the antioxidant effects of peptide were confirmed under the in vitro digestion model and oxidative damage HepG2 cells model. The results showed the antioxidant peptide could play better effect after digestion and protect the cells from oxidative damage. These data could expand the sequence data of antioxidant peptides and promote the high-value utilization of PPH.

In Silico Selection and Evaluation of Pugnins with Antibacterial and Anticancer Activity Using Skin Transcriptome of Treefrog (Boana pugnax)

In order to combat bacterial and cancer resistance, we identified peptides (pugnins) with dual antibacterial l-anticancer activity from the Boana pugnax (B. pugnax) skin transcriptome through in silico analysis. Pugnins A and B were selected owing to their high similarity to the DS4.3 peptide, which served as a template for their alignment to the B. pugnax transcriptome, as well as their function as part of a voltage-dependent potassium channel protein. The secondary peptide structure stability in aqueous medium was evaluated as well, and after interaction with the Escherichia coli (E. coli) membrane model using molecular dynamics. These pugnins were synthesized via solid-phase synthesis strategy and verified by Reverse phase high-performance liquid chromatography (RP-HPLC) and mass spectrometry. Subsequently, their alpha-helix structure was determined by circular dichroism, after which antibacterial tests were then performed to evaluate their antimicrobial activity. Cytotoxicity tests against cancer cells also showed selectivity of pugnin A toward breast cancer (MFC7) cells, and pugnin B toward prostate cancer (PC3) cells. Alternatively, flow cytometry revealed necrotic cell damage with a major cytotoxic effect on human keratinocytes (HaCaT) control cells. Therefore, the pugnins found in the transcriptome of B. pugnax present dual antibacterial-anticancer activity with reduced selectivity to normal eukaryotic cells.

Structural Changes and Evolution of Peptides During Chill Storage of Pork

In this work, we investigated changes in protein structures in vacuum-packed pork during chill storage and its impact on the in vitro protein digestion. Longissimus dorsi muscles were vacuum packed and stored at 4°C for 3 days. Samples were subjected to Raman spectroscopy, in vitro digestion and nano LC-MS/MS. The 3 d samples had lower α-helix content, but higher β-sheet, β-turn, and random coil contents than the 0 d samples (P < 0.05). SDS-PAGE revealed significant protein degradation in the 3 d samples and the differences in digested products across the storage time. Proteome analysis indicated that the 3 d samples had the higher susceptibility to digestion. Increasing protein digestibility was mainly attributed to the degradation of myofibrillar proteins. Thus, exposure of more enzymatic sites in loose protein structure during chill storage could increase protein degradation in meat.

Collagen Peptides from Swim Bladders of Giant Croaker (Nibea japonica) and Their Protective Effects against H2O2-Induced Oxidative Damage toward Human Umbilical Vein Endothelial Cells

Five different proteases were used to hydrolyze the swim bladders of Nibea japonica and the hydrolysate treated by neutrase (collagen peptide named SNNHs) showed the highest DPPH radical scavenging activity. The extraction process of SNNHs was optimized by response surface methodology, and the optimal conditions were as follows: a temperature of 47.2 °C, a pH of 7.3 and an enzyme concentration of 1100 U/g, which resulted in the maximum DPPH clearance rate of 95.44%. Peptides with a Mw of less than 1 kDa (SNNH-1) were obtained by ultrafiltration, and exhibited good scavenging activity for hydroxyl radicals, ABTS radicals and superoxide anion radicals. Furthermore, SNNH-1 significantly promoted the proliferation of HUVECs, and the protective effect of SNNH-1 against oxidative damage of H2O2-induced HUVECs was investigated. The results indicated that all groups receiving SNNH-1 pretreatment showed an increase in GSH-Px, SOD, and CAT activities compared with the model group. In addition, SNNH-1 pretreatment reduced the levels of ROS and MDA in HUVECs with H2O2-induced oxidative damage. These results indicate that collagen peptides from swim bladders of Nibea japonica can significantly reduce the oxidative stress damage caused by H2O2 in HUVECs and provides a basis for the application of collagen peptides in the food industry, pharmaceuticals, and cosmetics.

Novel bioactive peptides from enzymatic hydrolysate of Sardinelle (Sardinella aurita) muscle proteins hydrolysed by Bacillus subtilis A26 proteases

Sardinelle protein hydrolysate (SPH), prepared by treatment with Bacillus subtilis A26 proteases, was found to exhibit antibacterial, antioxidant and ACE-inhibitory activities. SPH, with a degree of hydrolysis of 4%, was fractionated by size exclusion chromatography on a Sephadex G-25 into five major fractions (F1-F5). F2, which exhibited the highest antibacterial and ACE-inhibitory activities, and F4, which exhibited the highest antibacterial and antioxidant activities, were further fractionated by reverse phase-high performance liquid chromatography (RP-HPLC) and then analysed using nano-ESI-LC-MS/MS to identify the sequences of peptides. Eight peptides were identified in the sub-fraction F2-A, nine peptides in the sub-fraction F4-B, and 45 peptides in F4-C. Identified peptides were found to share sequences with previously described bioactive peptides based on Biopep database. The results of this study suggest that SPH is a good source of natural bioactive peptides. Hence, it can be used as a potential ingredient in nutraceutical field.

Effect of cooking and simulated gastrointestinal digestion on the activity of generated bioactive peptides in aged beef meat

Ageing is widely used in the meat industry to improve tenderness mainly as a result of the breakdown of muscular proteins through the action of endopeptidases during storage time.

Development of an analytical strategy for the identification of potential bioactive peptides generated by in vitro tryptic digestion of fish muscle proteins

In the last years, food proteins and peptides are attracting great attention because of the emergence of a new field, that of food-derived bioactive peptides. This paper presents a comparison and evaluation of four different experiments for the identification of sarcoplasmic and myofibrillar fish peptides. This study is aimed at the development of a simple and fast method for the identification of peptides that could arise from fish meat if trypsin was the only digestive enzyme acting on fish meat proteins. In particular, we tested the use of ultrafiltration membranes with a molecular weight cutoff of 3,000 Da. Data analysis has shown that the experiment in which there is neither precipitation nor an ultrafiltration step performed better and allowed the identification of a larger number of peptides and potential antimicrobial peptides (AMPs); this workflow provided 473 and 398 total identified peptides and 44 and 18 AMPs for sarcoplasmic and myofibrillar extracts, respectively. This protocol is found to be faster and more straightforward than the other three tested workflows. The developed strategy could be also useful for other food matrices and could provide information about food quality and safety control.

Isolation and identification of antioxidative peptides from frog (Hylarana guentheri) protein hydrolysate by consecutive chromatography and electrospray ionization mass spectrometry

Frog (Hylarana guentheri) proteins were hydrolyzed by papain and Flavourzyme to obtain antioxidative peptides. The antioxidant activities of the frog protein hydrolysates (FPHs) were measured, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50=9.94±0.13 mg/mL), reducing power (0.39±0.01 at 5.0 mg/mL), and oxygen radical absorbance capacity (ORAC) value (789.15±75.10 μmol Trolox equivalents/g). The hydrolysates were purified by ultrafiltration, ion exchange chromatography, gel filtration chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). Through analysis of ESI-MS/MS, two dipeptides were identified as Leu/Ile-Lys (259.1607 Da) and Phe-Lys (293.1446 Da), respectively.

Effect of probiotic-fermented, genetically modified soy milk on hypercholesterolemia in hamsters

BACKGROUND/PURPOSE

The rapid progress of biotechnology and molecular biology has led to genetically modified (GM) crops becoming a part of agricultural production. There are concerns that the issues of the functional ingredients in GM products have not been addressed, such as the bioactivities of soy proteins and isoflavones. This study aimed to investigate the effects of probiotic-fermented GM soy milk on hypercholesterolemia, and atherosclerotic risks in hamsters.

METHODS

One hundred and twelve male Golden Syrian hamsters (Mesocricetus auratus) were randomly assigned into 14 groups of 8 animals each. Normal- and high-cholesterol experimental diets were supplemented with GM or non-GM soy milk with or without probiotic-fermentation for 8 weeks. Serum and fecal lipid levels were measured. Moreover, aortic plaque in artery were stained, and thiobarbituric acid reactive substance content, super oxide dismutase activity and caralase activity were determined.

RESULTS

GM or non-GM soy milk with or without probiotic-fermentation significantly decreased (p < 0.05) serum TC levels, compared with a high-cholesterol diet group. TC levels in hamsters fed GM soy milk were not significantly different from TC levels in the non-GM soy milk group (p > 0.05). GM soy milk groups can reduce risk of developing atherosclerosis through lowered oxidative stress and reduced atherosclerotic plaque formation in the aorta, and are thus at least equivalent to non-GM soy milk.

CONCLUSION

GM soy milk with or without probiotic-fermentation can improve hypercholesterolemia and reduce the risk of atherosclerosis, and is considered substantially equivalent to non-GM soy milk in terms of these bioactive functions.

Optimization of hydrolysis conditions, isolation, and identification of neuroprotective peptides derived from seahorse Hippocampus trimaculatus

Hippocampus trimaculatus is one of the most heavily traded seahorse species for traditional medicine purposes in many countries. In the present study, we showed neuroprotective effects of peptide derived from H. trimaculatus against amyloid-β42 (Aβ42) toxicity which are central to the pathogenesis of Alzheimer's diseases (AD). Firstly, H. trimaculatus was separately hydrolyzed by four different enzymes and tested for their protective effect on Aβ42-induced neurotoxicity in differentiated PC12 cells. Pronase E hydrolysate exerted highest protection with cell viability value of 88.33 ± 3.33 %. Furthermore, we used response surface methodology to optimize pronase E hydrolysis conditions and found that temperature at 36.69 °C with the hydrolysis time 20.01 h, enzyme to substrate (E/S) ratio of 2.02 % and pH 7.34 were the most optimum conditions. Following several purification steps, H. trimaculatus-derived neuroprotective peptides (HTP-1) sequence was identified as Gly-Thr-Glu-Asp-Glu-Leu-Asp-Lys (906.4 Da). HTP-1 protected PC12 cells from Aβ42-induced neuronal death with the cell viability value of 85.52 ± 2.22 % and up-regulated pro-survival gene (Bcl-2) expressions. These results suggest that HTP-1 has the potential to be used in treatment of neurodegenerative diseases, particularly AD. Identification, characterization, and synthesis of bioactive components derived from H. trimaculatus have the potential to replace or at least complement the use of seahorse as traditional medicine, which further may become an approach to minimize seahorse exploitation in traditional medicine.