Purification and identification of a novel hypotensive and antioxidant peptide from porcine plasma

Two Antihypertensive and Antioxidant Peptides Derived from Alaska Pollack (Theragra chalcograma) Skin: In Silico, In Vitro, and In Vivo Investigation

This study aimed to identify and characterize two novel dual-functional peptides with antihypertensive and antioxidant activities from byproducts of Alaska pollock skin (APS). Results showed that fifty-nine peptides were identified from APS, of which two peptides, GP1 (GSAGPAGPSGPRGP) and GP2 (LGDARNSPAPP), were predicted to exhibit the highest angiotensin-converting enzyme (ACE) inhibitory and antioxidant activities. GP1 and GP2 demonstrated favorable ACE inhibitory activities (IC50 values of 0.166 and 0.177 mmol/L, respectively) and significantly reduced blood pressure in hypertensive rats. Additionally, both peptides effectively scavenged 2,2'-casino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, with EC50 values of 0.273 and 0.629 mg/mL and protected HepG2 cells against H2O2-induced damage. Molecular docking revealed that the peptides interacted with amino acid residues within the active pocket and at the entrance channel of ACE, displaying mixed-competitive inhibition patterns. These peptides could also bind to the Kelch domain of Kelch-like ECH associating protein (Keap1), thereby promoting nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated transcriptional activation of antioxidant enzymes through the Keap1-Nrf2 pathway. The dual ACE inhibitory and antioxidant properties of APS peptides, coupled with high gastrointestinal stability, validated their utilization as multifunctional ingredients in antihypertensive functional foods, nutraceuticals, and peptide-based hydrogel development.

Antioxidant potential of peptides from poultry hemoglobin via probiotic-assisted hydrolysis: Deciphering mechanisms at the cellular level and through molecular dynamics simulations

Achieving the therapeutic goal of treating diseases by effectively controlling the excessive accumulation of intracellular free radicals is still very challenging, which motivates researchers to develop efficient novel antioxidant peptides from sustainable resources continuously. This study first pioneered a probiotic-assisted enzymatic hydrolysis of hemoglobin, which obtained 149 peptides. Two antioxidant peptides were rapidly screened using advanced molecular dynamics simulation techniques, revealing their molecular interaction mechanisms with Keap1. It was found that GLWGKV occupied six binding sites for Keap1 to form hydrogen bonds with Nrf2, whereas LIVYPW occupied two binding sites, and the binding free energy of GLWGKV to Keap1 was lower binding more stable. Cellular experiments confirmed that GLWGKV up-regulated the expression of related proteins and increased antioxidant enzyme activities, thereby attenuating H2O2-induced oxidative damage in Caco-2 cells. This research increases the economic added value of animal blood and demonstrates its great potential for development in functional foods.

Bioactive Peptides and Evaluation of Cardiac Cytoprotective Effects of Red Millet Yellow Wine as Functional Food

Red millet yellow wine, a functional beverage fermented from grain, has physiological functions including relieving cardiovascular diseases. However, the active components and mechanism of red millet yellow wine largely remain to be elucidated. In this study, bioactive peptides in red millet yellow wine and the cardiac cytoprotective effects were first investigated. A single-factor test and response surface method were used to optimize the solvent precipitation method to purify bioactive peptides. The final peptide content was up to 72.23%. Analysis of liquid chromatography-tandem mass spectrometry indicated a high antioxidative potential of the identified peptides. Multiple activity assays in vitro revealed that red millet yellow wine (1 mg/mL), particularly peptides (0.1 mg/mL), could protect H9c2 cells from H2O2-induced oxidative damage, thereby improving cell viability. At the mechanistic level, the antioxidant effect of bioactive peptides was achieved through strengthening antioxidative stress capacity and attributed to the activation of the Sirt1/Nrf2 pathway, indicating that peptides may be the main active components responsible for the cardiac cytoprotective effects of red millet yellow wine. These results are expected to provide a reference for further exploration of the health benefits of red millet yellow wine.

The Antioxidant Effects of Trypsin-Hydrolysate Derived from Abalone Viscera and Fishery By-Products, and the Angiotensin-I Converting Enzyme (ACE) Inhibitory Activity of Its Purified Bioactive Peptides

Abalone is a rich source of nutrition, the viscera of which are discarded as by-product during processing. This study explored the biological activities of peptides derived from abalone viscera (AV). Trypsin-hydrolysate of AV (TAV) was purified into three fractions using a Sephadex G-10 column. Nine bioactive peptides (VAR, NYER, LGPY, VTPGLQY, QFPVGR, LGEW, QLQFPVGR, LDW, and NLGEW) derived from TAV-F2 were sequenced. LGPY, VTPGLQY, LGEW, LDW, and NLGEW exhibited antioxidant properties, with IC50 values of 0.213, 0.297, 0.289, 0.363, and 0.303 mg/mL, respectively. In vitro analysis determined that the peptides VAR, NYER, VTPGLQY, QFPVGR, LGEW, QLQFPVGR, and NLGEW inhibited ACE, with IC50 values of 0.104, 0.107, 0.023, 0.023, 0.165, 0.004, and 0.146 mg/mL, respectively. The binding interactions of ACE-bioactive peptide complexes were investigated using docking analysis with the ZDCOK server. VTPGLQT interacted with HIS513 and TYR523, and QLQFPVGR interacted with HIS353, ALA354, GLU384, HIS513, and TYR523, contributing to the inhibition of ACE activity. They also interacted with amino acids that contribute to stability by binding to zinc ions. QFPVGR may form complexes with ACE surface sites, suggesting indirect inhibition. These results indicate that AV is a potential source of bioactive peptides with dual antioxidant and anti-hypertensive dual effects.

Purification, Identification and Molecular Docking of Novel Antioxidant Peptides from Walnut (Juglans regia L.) Protein Hydrolysates

Walnut protein isolate (WPI) was hydrolyzed using Alcalase for 0, 30, 60, 90, 120 and 150 min to investigate the effect of different hydrolysis times on the structure and antioxidant properties of walnut proteins. The identified peptides HADMVFY, NHCQYYL, NLFHKRP and PSYQPTP were used to investigate the structure-activity relationship by using LC-MS/MS and molecular docking. The kinetic equations DH = 3.72ln [1 + (6.68 E₀/S₀ + 0.08) t] were developed and validated to explore the mechanism of WIP hydrolysis by Alcalase. Structural characteristics showed that the UV fluorescence intensity and endogenous fluorescence intensity of the hydrolysates were significantly higher than those of the control. FTIR results suggested that the secondary structure gradually shifted from an ordered to a disordered structure. Enzymatic hydrolysis containing much smaller molecule peptides than WPI was observed by molecular weight distribution. In vitro, an antioxidant test indicated that Alcalase protease hydrolysis at 120 min showed more potent antioxidant activity than hydrolysates at other hydrolysis times. In addition, four new antioxidant peptides were identified by LC-MS/MS. Molecular docking indicated that these peptides could interact with ABTS through interactions such as hydrogen bonding and hydrophobic interactions. Thus, WPI hydrolysates could be used as potential antioxidants in the food and pharmaceutical industries.