Purification and Identification of Novel Myeloperoxidase Inhibitory Antioxidant Peptides from Tuna (Thunnas albacares) Protein Hydrolysates

Characterization of two novel angiotensin converting enzyme-inhibitory peptides from yellow tuna peptides: Inhibitory mechanism, transport route and network pharmacology analysis

Angiotensin-converting enzyme inhibitory peptides (ACEIPs) from natural food sources are effective alternatives for treating hypertension. This study aims to screen highly active ACEIPs from yellow tuna peptides, and to elucidate their inhibitory mechanism, stability, transport mechanism and potential antihypertensive mechanism by a multiple approach. Two novel ACEIPs STHPHF (IC50 = 30.71 μg/mL) and LTFSY (IC50 = 20.72 μg/mL) were screened by bio-activity guided approach and de novo sequencing. Inhibition kinetics and molecular docking indicated that STHPHF demonstrated a mixed inhibitor, whereas LTFSY acted as a competitive inhibitor of ACE. STHPHF and LTFSY bound to different active pockets of ACE mainly through hydrogen bonding and hydrophobic interactions. In addition, these two peptides exhibited good stability at 20-100 °C and at pH 2-10, but showed certain activity loss during gastrointestinal digestion, whereas LTFSY has better digestive stability than STHPHF. Caco-2 cells monolayer model assays indicated that LTFSY is mainly absorbed through bypass transport, and possesses an efflux mode related to multidrug-resistant protein. Network pharmacology and molecular docking analysis suggested that LTFSY regulates hypertension by multiple pathway and multi-target mode, AGTR1, MAPK8, NOS3, and RHOA maybe the major targets. This study highlights the promising potential of peptide LTFSY for lowering blood pressure.

Determination of the Inhibitory Potential of Chalcones on Myeloperoxidase Enzyme Activity: In vitro and Molecular Docking Studies

Myeloperoxidase (MPO) is a highly abundant hemoprotein in neutrophils and monocytes. It has a crucial function in immunological surveillance and the body's defensive systems. Nevertheless, there is a strong correlation between elevated MPO activity and the development and advancement of inflammatory processes. Chalcone derivatives serve as fundamental components of pharmaceutical raw materials, which have been extensively utilized for the treatment of several ailments. In this study, it was studied the effect of some chalchones on MPO activity. Chalcones (1-6) strongly inhibited MPO with IC50s in the micromolar range of 0.05-0.828 µM. In particular, 4,4'-difluorochalcone (3) exhibited the best MPO inhibitory impact with IC50 of 0.05 µM. Additionally, molecular docking experiments were conducted to predict the binding affinities and interactions of the chalcone derivatives with the MPO active site. The docking results revealed that all tested compounds exhibited favorable binding energies, with ΔG Vina values ranging from -7.6 to -8.4 kcal/mol. Compound 3 demonstrated the strongest binding affinity (-8.4 kcal/mol), forming key hydrogen bonds with Gln91 and His95, and halogen interactions with the fluorine atoms, which may account for its enhanced inhibitory activity. These combined in vitro and in silico results suggest that chalcone derivatives hold significant potential as therapeutic candidates targeting MPO.

Exploring the separation, characterization and antioxidant activity of proteins and peptides from selected seagrasses in Palk Bay region of Tamil Nadu in India

In this study, five seagrass species Halodule uninervis, Thalassia hemprichii, Enhalus acoroides, Cymodocea serrulata, and Syringodium isoetifolium collected from the Mandapam coastal region of Rameswaram (Palk Bay region), Tamil Nadu, India, were selected to identify the antioxidant-rich proteins/peptides. The primary objective was to identify the proteins/peptides present in these seagrass filtrates extracted by using four different pH-based buffer extracts and to assess their antioxidant activity. Among the various buffer extracts, 0.1 M Citrate buffer (pH 5.5) exhibited the highest proteins/peptides recovery in all species. Of these, S. isoetifolium showed the highest recovery percentage (20.18 %) in the 10 kDa filtrate. Notably, the 3 kDa filtrate of S. isoetifolium demonstrated the highest antioxidant activity (83 %). The peptides sequences in all five seagrass samples were identified by MALDI - TOF MS analysis, Furthermore, in silico protein-peptide docking studies were conducted to assess the interaction of the identified peptides with key antioxidant-related targets, including superoxide dismutase, xanthine oxidase, inducible nitric oxide synthase, keap 1 protein, and myeloperoxidase. With all these targets, the peptide derived from S. isoetifolium exhibited better binding affinity. This study emphasized that the potential peptides identified from seagrass are the natural antioxidant sources that can be used to treat disorders linked to oxidative stress.

Evaluation of the Antibacterial and Antioxidant Properties of Chemical Constituents of the Roots of Woodfordia uniflora: An Integrated Approach of Experimental and Computational Study

Woodfordia uniflora is a medicinal plant used for the treatment of malaria, toothache, and stomach problems. The root parts of the plant are also used for healing liver disorders. Silica gel chromatography separation of CH2Cl2/MeOH (1:1) and MeOH extracts of roots of W. uniflora result in the isolation of three compounds, namely, bergenin (1), β-sitosterol (2), and epigallocatechin 3-gallate (3), reported herein for the first time from the plant. The structure of the isolated compounds was elucidated using NMR (1D and 2D) techniques. Disk diffusion and DPPH assay were used to evaluate the antibacterial and antioxidant activities, respectively. Molecular docking was done by the AutoDock Vina 4.2 program. The pharmacokinetics and toxicity profile of compounds were predicted by Swiss ADME and Pro Tox II online servers. GC-MS analysis roots of W. uniflora result in the identification of five compounds, of which palmitic acid (34.9%) was the major constituent. The antibacterial activity result indicated that the oil extract had promising activity against P. aeruginosa, E. coli, S. pyogenes, and S. aureus with IZ of 14.3 ± 0.81, 15.0 ± 0.0, 15.6 ± 0.47, and 17.6 ± 0.47 mm, respectively, at 5 mg/mL, compared to ciprofloxacin (1Z 27-30.0 ± 0.0 mm) at 30 μg/mL. MeOH and CH2Cl2/MeOH (1:1) extract showed inhibition against E. coli (IZ of 13.6 ± 0.47 mm) and P. aeruginosa (IZ of 10.0 ± 0.0 mm), respectively, at 200 mg/mL. Bergenin (1) and β-sitosterol (2) also displayed maximum inhibition of E. coil (IZ of 11.6 ± 0.47) and S. aureus (11.0 ± 0.0 mm), respectively, at 5 mg/mL. The antioxidant activity results showed that CH2Cl2/MeOH (1:1) and MeOH extracts, bergenin (1), and compound 3 displayed potent scavenging DPPH radical with a percentage of inhibition of 76.8 ± 0.12, 77.8 ± 0.08, 71.4 ± 0.08, and 91.2 ± 0.16, respectively, compared to ascorbic acid (93.2% ± 0.04%) at 100 μg/mL. The molecular docking analysis showed that all compounds (1-3) exhibited minimum binding energy toward PDB ID: 1HD2 (-5.2 to -6.3 kcal/mol), compared to ascorbic acid (-5.6 kcal/mol), and toward PDB ID: 1DNU (-8.0 to -10.7 kcal/mol) receptors, compared to ascorbic acid (-5.7 kcal/mol). Toward the PDB ID: 4FM9 receptor, β-sitosterol (2) and compound 3 exhibited the best binding free energy of -9.1 and -9.8 kcal·mol, respectively, compared to vosaroxin (-7.8 kcal/mol). The drug-likeness analysis result indicated that bergenin (1) and β-sitosterol (2) obeyed four and five criteria of Lipinski's rule, respectively, and are more likely to be administered orally. The in silico toxicity analysis showed none of the compounds would be cytotoxic, mutagenic, or hepatotoxic. The in vitro antioxidant and antibacterial results supported by in silico analysis demonstrated that the roots of W. uniflora have the potential to be therapeutic agents for bacterial infections and free radical-inducing diseases.

Regulation of redox enzymes by nutraceuticals: a review of the roles of antioxidant polyphenols and peptides

Redox enzymes are essential components of the cellular defence system against oxidative stress, which is a common factor in various diseases. Therefore, understanding the role of bioactive nutraceuticals in modulating the activity of these enzymes holds immense therapeutic potential. This paper provides a comprehensive review of the regulation of redox enzymes in cell and animal models by food-derived bioactive nutraceuticals, focusing on polyphenols and peptides. Specifically, this paper discusses the regulation of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), NAPDH oxidase, xanthine oxidase (XO), myeloperoxidase (MPO), and haem oxygenase (HO) in cell and animal models. Polyphenols, which are abundant in fruits, vegetables, and beverages, have diverse antioxidant properties, including direct scavenging of reactive oxygen species and regulation of transcription factors such as nuclear factor erythroid 2-related factor 2, which leads to the increased expression of the redoxenzymes SOD, HO, and GPx. Similarly, bioactive peptides from various food proteins can enhance antioxidative enzyme activity by regulating gene expression and directly activating the enzyme CAT. In other cases, an antioxidative response requires the downregulation or inhibition of the redox enzymes XO, MPO, and NAPDH oxidase. This paper highlights the potential of bioactive nutraceuticals in mitigating oxidative stress-related diseases and their mechanisms in modulating the redox enzyme expression or activity. Furthermore, the review highlights the need for further research to uncover new therapeutic strategies using nutraceuticals for enhancing cellular antioxidant defence mechanisms and improving health outcomes.

Tuna sidestream valorization: a circular blue bioeconomy approach

Tuna is an economically significant seafood, harvested throughout the world, and is heavily traded due to its high nutritional quality and consumer acceptance. Tuna meat is rich in essential nutrients such as amino acids, polyunsaturated fatty acids (PUFA), and trace minerals. The huge volume of solid and liquid sidestreams generated during the processing stages of tuna is creating environmental and socioeconomic challenges in coastal areas. Different products such as fish meal, protein hydrolysates, collagen, enzymes, oil, and bone powder can be produced from tuna sidestreams. Using different nutrient recovery technologies like enzymatic hydrolysis, chemical processing, and green technologies, various categories of product value chains can be created in line with the conventional processing industry. This review attempts to provide a route map for the tuna industry for achieving the circular blue-bioeconomic objectives and reorient the irregular utilization pattern into a sustainable and inclusive path.

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

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

Novel and efficient techniques in the discovery of antioxidant peptides

As a research hotspot in food science and nutrition, antioxidant peptides can function by scavenging free radicals, inhibiting peroxides, and chelating metal ions. Therefore, how to efficiently discover and screen antioxidant peptides has become a key issue in research and production. Traditional discovery methods are time-consuming and costly, but also challenging to resolve the quantitative structure-activity relationship of antioxidant peptides. Several novel techniques, including artificial intelligence, molecular docking, bioinformatics, quantum chemistry, phage display, switchSENSE, surface plasmon resonance, and fluorescence polarization, are emerging rapidly as solutions. These techniques possess efficient capability for the discovery of antioxidant peptides, even with the potential for high-throughput screening. In addition, the quantitative structure-activity relationship can be resolved. Notably, combining these novel techniques can overcome the drawbacks of a single one, thus improving efficiency and expanding the discovery horizon. This review has summarized eight novel and efficient techniques for discovering antioxidant peptides and the combination of techniques. This review aims to provide scientific evidence and perspectives for antioxidant peptide research.

Antioxidative, Glucose Management, and Muscle Protein Synthesis Properties of Fish Protein Hydrolysates and Peptides

The marine environment is an excellent source for many physiologically active compounds due to its extensive biodiversity. Among these, fish proteins stand out for their unique qualities, making them valuable in a variety of applications due to their diverse compositional and functional properties. Utilizing fish and fish coproducts for the production of protein hydrolysates and bioactive peptides not only enhances their economic value but also reduces their potential environmental harm, if left unutilized. Fish protein hydrolysates (FPHs), known for their excellent nutritional value, favorable amino acid profiles, and beneficial biological activities, have generated significant interest for their potential health benefits. These hydrolysates contain bioactive peptides which are peptide sequences known for their beneficial physiological effects. These biologically active peptides play a role in metabolic regulation/modulation and are increasingly seen as promising ingredients in functional foods, nutraceuticals and pharmaceuticals, with potential to improve human health and prevent disease. This review aims to summarize the current in vitro, cell model (in situ) and in vivo research on the antioxidant, glycaemic management and muscle health enhancement properties of FPHs and their peptides.

Novel Antioxidant Self-Assembled Peptides Extracted from Azumapecten farreri Meat: In Vitro- and In Silico-Assisted Identification

Previous studies have found that the self-assembled supramolecules of Azumapecten farreri meat peptides have antioxidant effects. Therefore, this study aims to isolate and identify novel antioxidant peptides with self-assembly characteristics and analyze their structure-activity relationship through molecular docking and molecular dynamics simulation. The in vitro results show that as the purification steps increased, the antioxidant activity of peptides became stronger. Additionally, the purification step did not affect its pH-responsive self-assembly. Using LC-MS/MS, 298 peptide sequences were identified from the purified fraction PF1, and 12 safe and antioxidant-active peptides were acquired through in silico screening. The molecular docking results show that they had good binding interactions with key antioxidant-related protein ligands (KEAP1 (Kelch-like ECH-associated protein 1) and MPO (myeloperoxidase)). The peptide QPPALNDSYLYGPQ, with the lowest docking energy, was selected for a 100 ns molecular dynamics simulation. The results show that the peptide QPPALNDSYLYGPQ exhibited excellent stability when docked with KEAP1 and MPO, thus exerting antioxidant effects by regulating the KEAP1-NRF2 pathway and inhibiting MPO activity. This study further validates the antioxidant and self-assembling properties of the self-assembled supramolecules of Azumapecten farreri meat peptide and shows its potential for developing new, effective, and stable antioxidants.

Valorization of Yellowfin Tuna Tails: From Proteolytic Enzyme Production to Gelatin and Antioxidant Hydrolysate Extraction

This study investigates the valorization potential of yellowfin tuna (Thunnus albacares) tails to produce high-value commercial products. Firstly, the tuna tails were placed in a perforated stainless-steel cylinder, and hydraulic pressure was applied to separate the skin from the muscle in the tails. The extracted muscle was then utilized as a nitrogen source for the growth of the proteolytic enzyme producer Bacillus subtilis, while the skins were employed for gelatin extraction. The proteases from B. subtilis were partially purified and used to produce antioxidant peptides from the obtained gelatin. The gelatin formed a gel upon cooling, with gelling and melting temperatures of 16 °C and 22 °C, respectively, and a Bloom strength of approximately 160. Response Surface Methodology (RSM) was employed to determine the optimal hydrolysis conditions to achieve the highest antioxidant activity (35.96% measured as DPPH radical scavenging activity), which were 50 °C and 6.5 IU of enzyme. The findings emphasize the importance of an integrated approach to maximize the value of tuna by-products, promoting sustainability within the framework of a circular bioeconomy. Overall, these results contribute to the efficient utilization of tuna by-products, waste reduction, and enhanced economic viability of the tuna industry.

Statistical Characterization of Food-Derived α-Amylase Inhibitory Peptides: Computer Simulation and Partial Least Squares Regression Analysis

α-Amylase inhibitory peptides are used to treat diabetes, but few studies have statistically characterized their interaction with α-amylase. This study performed the molecular docking of α-amylase with inhibitory peptides from published papers. The key sites, side chain chargeability, and hydrogen bond distribution characteristics were analyzed. Molecular dynamics simulated the role of key sites in complex stability. Moreover, partial least squares regression (PLSR) was used to analyze the contribution of different amino acids in the peptides to inhibition. The results showed that, for the α-amylase molecule, His201 and Gln63, with the highest interaction numbers (INs, 15, 15) and hydrogen bond values (HBVs, 11.50, 10.33), are the key sites on α-amylase, and amino acids with positively charged side chains were important for inhibitory activity. For the inhibitory peptides, Asp and Arg had the highest HBVs, and amino acids with charged side chains were more likely to form hydrogen bonds and exert inhibitory activity. In molecular dynamics simulations, peptides involving key binding sites formed more stable complexes with α-amylase than α-amylase alone, suggesting enhanced inhibitory effects. Further, PLSR results showed that amino acids close to the N-terminus of the inhibitory peptide, located in the third and fifth positions, were significantly correlated with its inhibitory activity. In conclusion, this study provides a new approach to developing and screening α-amylase inhibitors.

Tuna trimmings (Thunnas albacares) hydrolysate alleviates immune stress and intestinal mucosal injury during chemotherapy on mice and identification of potentially active peptides

In this study, Tuna trimmings (Thunnas albacares) protein hydrolysate (TPA) was produced by alcalase. The anti-tumor synergistic effect and intestinal mucosa protective effect of TPA on S180 tumor-bearing mice treated with 5-fluorouracil (5-FU) chemotherapy were investigated. The results showed that TPA can enhance the anti-tumor effect of 5-FU chemotherapy, as evident by a significant reduction in tumor volume observed in the medium and high dose TPA+5-FU groups compared to the 5-FU group (p < 0.001). Moreover, TPA significantly elevated the content of total protein and albumin in all TPA dose groups (p < 0.01, p < 0.001), indicating its ability to regulate the nutritional status of the mice. Furthermore, histopathological studies revealed a significant increase in the height of small intestinal villi, crypt depth, mucosal thickness, and villi area in the TPA+5-FU groups compared to the 5-FU group (p < 0.05), suggesting that TPA has a protective effect on the intestinal mucosa. Amino acid analysis revealed that TPA had a total amino acid content of 66.30 g/100 g, with essential amino acids accounting for 30.36 g/100 g. Peptide molecular weight distribution analysis of TPA indicated that peptides ranging from 0.25 to 1 kDa constituted 64.54%. LC-MS/MS analysis identified 109 peptide sequences, which were predicted to possess anti-cancer and anti-inflammatory activities through database prediction. Therefore, TPA has the potential to enhance the antitumor effects of 5-FU, mitigate immune depression and intestinal mucosal damage induced by 5-FU. Thus, TPA could be serve as an adjuvant nutritional support for malnourished patients undergoing chemotherapy.

A review on the processing of functional proteins or peptides derived from fish by-products and their industrial applications

To understand the production and characteristics of protein hydrolysates pertaining to individual fish species, we selected and analyzed the most important commercial fish species according to the market value based on the Statistics on International Exports of Fishery Commodities by Food and Agriculture Organization. Accordingly, salmon, shrimp, cod, tuna, squid, and herring are marine species with high global value. Peptides obtained from their by-products were predominant in hydrophobic amino acids such as alanine, phenylalanine, methionine, proline, valine, tyrosine, tryptophan, leucine, and isoleucine. Bioactive peptides are short with a length of 2-20 amino acids. They remain inactive when they are within their parent proteins. Low molecular weight (0.3-8 kDa) peptides from hydrolyzed protein are easily digestible, readily absorbed by the body and are water-soluble. The hydrophobic nature contributes to their bioactivity, which facilitates their interactions with the membrane lipid bilayers. Incomplete hydrolysis results in low yields of hydrophobic amino acids. The glycosylation type of the resulting peptide fragment determines the different applications of the hydrolysate. The degree of conservation of the glycosidic residues and the size of the peptides are influenced by the method used to generate these hydrolysates. Therefore, it is crucial to explore inexpensive novel methodologies to generate bioactive peptides. According to the current studies, a unified approach (in silico estimation coupled with peptidomics) can be used for the identification of novel peptides with diverse physiological and technological functions. From an industrial perspective, the reusability of immobilized enzymes and membrane separation techniques (e.g., ultrafiltration) on marine by-products can offer low operating costs and higher yield for large-scale production of bioactive peptides. This review summarizes the production processes and essential characteristics of protein hydrolysates from fish by-products and presents the advances in their application.