Identification, functional gastrointestinal stability and molecular docking studies of lentil peptides with dual antioxidant and angiotensin I converting enzyme inhibitory activities

Selenium-chelating corn oligopeptide as a potential antioxidant supplement: investigation of the protein conformational changes and identification of the antioxidant fragment composition

A selenium-chelating corn oligopeptide (Se-COP) with high protein and low molecular weight was prepared as a selenium supplement. We utilized infrared (IR), ultraviolet (UV), and circular dichroism (CD) spectroscopy, 1-anilinonaphthalene-8-sulfonate (ANS)-binding fluorescence spectra, and isothermal titration calorimetry (ITC) to analyze and describe Se-COP and its reactions. It was concluded that the chelation reaction was a spontaneous process driven by enthalpy and entropy, with ΔH=3.79 × 104 ± 4075 cal/mol, ΔS = 146 cal/mol, ΔG = –23356.30 ± 126.94 cal/mol, binding constant Ka = 1.18 × 104 ± 855 M–1, and binding site number n = 0.13 ± 0.0126, and described as coordination bonds forming and hydrophobic interaction, as well as protein conformational changes including secondary and tertiary hydrophobic structure. Se-COP had strong antioxidant capacity, and mass spectrometry (MS) was used to identify the antioxidant peptide fragment, which was characterized as LLPPY and quantified at 428.95 ng/mg. This study indicated that Se-COP prepared by chelation may be a Se supplement with antioxidant capacity that can be applied in functional foods or ingredients.

The Effect of Sprouting in Lentil (Lens culinaris) Nutritional and Microbiological Profile

Biological and vegetarian raw food products, in particular based on legume sprouts, are an increasing food trend, due to their improved nutritional value when compared to seeds. Herein, protein and mineral profiles were studied in 12 lentil varieties, with varieties Du Puy, Kleine Schwarze, Rosana, Flora, Große Rote and Kleine Späths II demonstrating the highest protein percentages. After sprouting, protein percentages increased significantly in 10 of the 12 varieties, with the highest increases ranging between 20–23% in Dunkelgrün Marmorierte, Du Puy, Große Rote and Kleine Späths II varieties. While Fe concentration was significantly decreased in three varieties (Samos, Große Rote and Kleine Späths II), Zn and Mn were positively impacted by sprouting (p ≤ 0.05). Magnesium concentration was not affected by sprouting, while Ca and K had percentage increases between 41% and 58%, and 28% and 30%, respectively, in the best performing varieties (Kleine Schwarze, Dunkelgrün Marmorierte, Samos and Rosana). Regardless of the associated nutritional benefits, issues pertaining to sprouts microbiological safety must be ensured. The best results for the disinfection protocols were obtained when combining the seed treatment with SDS reagent followed by an Amukine application on the sprouts, which did not affect germination rates or sprout length. The increasing levels of sprout consumption throughout the world require efficient implementation of safety measures, as well as a knowledge-based selection for the nutritional quality of the seeds.

Bioactive Peptide Tempe Made from Mucuna pruriens (L) DC as an Inhibitor of Angiotensin-I-Converting Enzyme (ACE) in a Digestion Simulation

Mucuna pruriens (L) DC tempe is a food that functions as an inhibitor of the angiotensin-I-converting enzyme (ACE). The purpose of this research was to study the activity of M. pruriens tempe peptides during the digestive process in vitro with pepsin-pancreatin, and absorption of peptides in the small intestine using the inverted intestinal sac method. Our results show that M. pruriens had the highest ACE-inhibiting activity after digestion in vitro after fermentation for 72 h (F72). F72 peptide absorption (%) and ACE-inhibitory activity of the absorbed peptides did not significantly differ between the different segments of the small intestine (duodenum, jejunum, and ileum). These results demonstrate that F72 tempe maintains ACE-inhibitory activity in each segment of the small intestine after both digestion and absorption.

Legume Proteins as a Promising Source of Anti-Inflammatory Peptides

Legume proteins are precursors of bioactive components, such as peptides. In the present paper, different types of legume as sources of bioactive peptides and hydrolysates are considered and discussed based on their anti-inflammatory effect. Peptides with anti-inflammatory activity were included from in vitro and in vivo studies. Current strategies for obtaining bioactive peptides, as well as their structure and impact on health, were also reviewed. It was discovered that peptides derived from legume protein, mainly soybean and bean, can regulate several inflammatory markers, which include prostaglandin E2 (PGE2), nitric oxide (NO), inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX- 2), cytokines, and chemokines. So far, lunasin, VPY and γ-glutamyl peptides have been identified with anti-inflammatory activity but their mechanisms have not been fully elucidated. Furthermore, it is necessary to gather more information about hydrolysates containing peptides and single peptides with antiinflammatory activity. Considering the wide diversity, legume may be promising components to produce peptides efficient to ameliorate inflammatory disorders.

Structural and molecular bases of angiotensin-converting enzyme inhibition by bovine casein-derived peptides: an in silico molecular dynamics approach

The angiotensin-converting enzyme (ACE) plays a key role in blood pressure regulation process, and its inhibition is one of the main drug targets for the treatment of hypertension. Though various peptides from milk proteins are well-known for their ACE-inhibitory capacity, research devoted to understand the molecular bases of such property remain scarce, specifically for such peptides. Therefore, in this work, computational molecular docking and molecular dynamics calculations were performed to enlighten the intermolecular interactions involved in ACE inhibition by six different casein-derived peptides (FFVAPFPEVFGK, FALPQYLK, ALNEINQFYQK, YLGYLEQLLR, HQGLPQEVLNENLLR and NAVPITPTLNR). Two top ranked docking poses for each peptide (one with N- and the other C-terminal peptide extremity oriented towards the ACE active site) were selected for dynamic simulations (50 ns; GROMOS53A6 force field), and the results were correlated to in vitro ACE inhibition capacity. Two molecular features appeared to be essential for peptides to present high ACE inhibition capacity in vitro: i) to interact with the S1 active site residues (Ala354, Glu384, and Tyr523) by hydrogen bonds; ii) to interact with Zn²⁺ coordinated residues (His383, His387, and Glu411) by short-lenght hydrogen bonds, as observed in the cases of ALNEINQFYQK (IACE = 80.7%), NAVPITPTLNR (IACE = 80.7%), and FALPQYLK (IACE = 79.0%). Regardless of the temporal stability of these strong interactions, they promoted some disruption of Zn²⁺ tetrahedral coordination during the molecular dynamics trajectories, and were pointed as the main reason for the greatest ACE inhibition by these peptides. On the other hand, peptides with intermediate inhibition capacity (50% < I_ACE < 45%) interacted mainly by weaker interactions (e.g.: electrostatic and hydrophobic) with the Zn²⁺ coordinated residues, and were not able to change significantly its tetrahedral coordination structure. These findings may: i) assist the discrimination in silico of "good" and "bad" ACE-inhibitory peptides from other food sources, and/or ii) aid in designing de novo new molecules with ACE-inhibitory capacity. Communicated by Ramaswamy Sarma.

Egg-White-Derived Antioxidant Peptide as an Efficient Nanocarrier for Zinc Delivery through the Gastrointestinal System

An antioxidant peptide derived from egg white, Asp-His-Thr-Lys-Glu (DHTKE), possesses specific amino acids related to zinc delivery. This study aimed to demonstrate the molecular basis of interactions between the egg white peptide (DHTKE) and zinc ions and investigate the effect of the DHTKE-Zn complex on zinc delivery through the gastrointestinal system. Approximately one DHTKE molecule can bind one zinc ion (n = 1.048 ± 0.085) through its carboxyl, amino, and imidazole nitrogen groups on Asp, His, and Glu. The formed DHTKE-Zn complex presented uniformly distributed globular particles with a particle size of 100-500 nm and underwent dissociation and re-chelation during gastrointestinal digestion. Moreover, the DHTKE peptide mostly remained stable, with a retention rate of 98.32% under gastrointestinal digestion, although one degradation product (DHTK) was identified by nanoscale liquid chromatography-electrospray ionization-tandem mass spectrometry in the gastrointestinal digests; the effectiveness of DHTKE-Zn digests on enhancing absorption of zinc was comparable to that of the initial complex.

Novel ACE Inhibitory Peptides Derived from Simulated Gastrointestinal Digestion in Vitro of Sesame (Sesamum indicum L.) Protein and Molecular Docking Study

The aim of this study was to isolate and identify angiotensin I-converting enzyme (ACE) inhibitory peptides from sesame protein through simulated gastrointestinal digestion in vitro, and to explore the underlying mechanisms by molecular docking. The sesame protein was enzymatically hydrolyzed by pepsin, trypsin, and α-chymotrypsin. The degree of hydrolysis (DH) and peptide yield increased with the increase of digest time. Moreover, ACE inhibitory activity was enhanced after digestion. The sesame protein digestive solution (SPDS) was purified by ultrafiltration through different molecular weight cut-off (MWCO) membranes and SPDS-VII (< 3 kDa) had the strongest ACE inhibition. SPDS-VII was further purified by NGC Quest™ 10 Plus Chromatography System and finally 11 peptides were identified by Nano UHPLC-ESI-MS/MS (nano ultra-high performance liquid chromatography-electrospray ionization mass spectrometry/mass spectrometry) from peak 4. The peptide GHIITVAR from 11S globulin displayed the strongest ACE inhibitory activity (IC50 = 3.60 ± 0.10 μM). Furthermore, the docking analysis revealed that the ACE inhibition of GHIITVAR was mainly attributed to forming very strong hydrogen bonds with the active sites of ACE. These results identify sesame protein as a rich source of ACE inhibitory peptides and further indicate that GHIITVAR has the potential for development of new functional foods.

Whey-Derived Peptides Interactions with ACE by Molecular Docking as a Potential Predictive Tool of Natural ACE Inhibitors

Several milk/whey derived peptides possess high in vitro angiotensin I-converting enzyme (ACE) inhibitory activity. However, in some cases, poor correlation between the in vitro ACE inhibitory activity and the in vivo antihypertensive activity has been observed. The aim of this study is to gain insight into the structure-activity relationship of peptide sequences present in whey/milk protein hydrolysates with high ACE inhibitory activity, which could lead to a better understanding and prediction of their in vivo antihypertensive activity. The potential interactions between peptides produced from whey proteins, previously reported as high ACE inhibitors such as IPP, LIVTQ, IIAE, LVYPFP, and human ACE were assessed using a molecular docking approach. The results show that peptides IIAE, LIVTQ, and LVYPFP formed strong H bonds with the amino acids Gln 259, His 331, and Thr 358 in the active site of the human ACE. Interestingly, the same residues were found to form strong hydrogen bonds with the ACE inhibitory drug Sampatrilat. Furthermore, peptides IIAE and LVYPFP interacted with the amino acid residues Gln 259 and His 331, respectively, also in common with other ACE-inhibitory drugs such as Captopril, Lisinopril and Elanapril. Additionally, IIAE interacted with the amino acid residue Asp 140 in common with Lisinopril, and LIVTQ interacted with Ala 332 in common with both Lisinopril and Elanapril. The peptides produced naturally from whey by enzymatic hydrolysis interacted with residues of the human ACE in common with potent ACE-inhibitory drugs which suggests that these natural peptides may be potent ACE inhibitors.

A biotechnological approach for the production of branched chain amino acid containing bioactive peptides to improve human health: A review

Improper nutrition provokes many types of chronic diseases and health problems, which consequently are associated with particularly high costs of treatments. Nowadays, consumer's interest in healthy eating is shifting towards specific foods or food ingredients. As a consequence, bioactive peptides as a promising source of health promoting food additives are currently an intensely debated topic in research. Process design is still on its early stages and is significantly influenced by important preliminary decisions. Thus, parameters like peptide bioactivity within the product, selection of the protein source, enzyme selection for hydrolysis, peptide enrichment method, as well as stability of the peptides within the food matrix and bioavailability are sensitive decision points, which have to be purposefully coordinated, as they are directly linked to amino acid content and structure properties of the peptides. Branched chain amino acids (BCAA) are essential components for humans, possessing various important physiologic functions within the body. Incorporated within peptide sequences, they may induce dual functions, when used as nutraceuticals in functional food, thus preserving the foodstuff and prevent several widespread diseases. Furthermore, there is evidence that consuming this peptide-class can be a nutritional support for elderly people or improve human health to prevent diseases caused by incorrect nutrition. Based on the knowledge about the role of BCAA within various peptide functions, discussed in the review, special attention is given to different approaches for systematic selection of the protein source and enzymes used in hydrolysis, as well as suitable peptide enrichment methods, thereby showing current trends in research.

Comparison of an angiotensin-I-converting enzyme inhibitory peptide from tilapia (Oreochromis niloticus) with captopril: inhibition kinetics, in vivo effect, simulated gastrointestinal digestion and a molecular docking study

BACKGROUND

In order to utilize tilapia skin gelatin hydrolysate protein, which is normally discarded as industrial waste in the process of fish manufacture, we study the in vivo and in vitro angiotensin-I-converting enzyme (ACE) inhibitory activity of the peptide Leu-Ser-Gly-Tyr-Gly-Pro (LSGYGP). The aim was to provide a pharmacological basis of the development of minimal side effects of ACE inhibitors by comparative analysis with captopril in molecular docking.

RESULTS

This peptide from protein-rich wastes showed excellent ACE inhibitory activity (IC₅₀  = 2.577 μmol L^-1 ) and exhibited a mixed noncompetitive inhibitory pattern with Lineweaver-Burk plots. Furthermore, LSGYGP and captopril groups both showed significant decreases in blood pressure after 6 h and maintained good digestive stability over 4 h. Molecular bond interactions differentiate competitive captopril upon hydrogen bond interactions and Zn(II) interaction. The C-terminal Pro generates three interactions (hydrogen bonds, hydrophilic interactions and Van der Waals interactions) in the peptide and effectively interacts with the S1 and S2 pockets of ACE.

CONCLUSION

LSGYGP, with an IC₅₀ value of 2.577 μmol L^-1 , has an antihypertensive effect in spontaneously hypertensive rats. Through comparison with captopril, this study revealed that LSGYGP may be a potential food-derived ACE inhibitory peptide and could act as a functional food ingredient to prevent hypertension. © 2019 Society of Chemical Industry.

Computational and Pharmacogenomic Insights on Hypertension Treatment: Rational Drug Design and Optimization Strategies

Background::

Hypertension is a prevalent cardiovascular complication caused by genetic and nongenetic factors. Blood pressure (BP) management is difficult because most patients become resistant to monotherapy soon after treatment initiation. Although many antihypertensive drugs are available, some patients do not respond to multiple drugs. Identification of personalized antihypertensive treatments is a key for better BP management.

Objective::

This review aimed to elucidate aspects of rational drug design and other methods to develop better hypertension management.

Results::

Among hypertension-related signaling mechanisms, the renin-angiotensin-aldosterone system is the leading genetic target for hypertension treatment. Identifying a single drug that acts on multiple targets is an emerging strategy for hypertension treatment, and could be achieved by discovering new drug targets with less mutated and highly conserved regions. Extending pharmacogenomics research to include patients with hypertension receiving multiple antihypertensive drugs could help identify the genetic markers of hypertension. However, available evidence on the role of pharmacogenomics in hypertension is limited and primarily focused on candidate genes. Studies on hypertension pharmacogenomics aim to identify the genetic causes of response variations to antihypertensive drugs. Genetic association studies have identified single nucleotide polymorphisms affecting drug responses. To understand how genetic traits alter drug responses, computational screening of mutagenesis can be utilized to observe drug response variations at the protein level, which can help identify new inhibitors and drug targets to manage hypertension.

Conclusions::

Rational drug design facilitates the discovery and design of potent inhibitors. However, further research and clinical validation are required before novel inhibitors can be clinically used as antihypertensive therapies.

Design and evaluation of four novel tripeptides as potent angiotensin converting enzyme (ACE) inhibitors with anti-hypertension activity

The current study investigated the angiotensin-converting enzyme (ACE) inhibitory activity of 4 synthetic tripeptides. All the peptides showed enzyme inhibitory activity, especially two promising ones, TTP (Thea-Thea-Pro) and gAgAP (GABA-GABA-Pro), with IC₅₀ values of 0.92 and 3.4 μmol/L, respectively. Enzyme inhibition kinetics determined by Lineweaver-Burk plots revealed that TTP and gAgAP were competitive inhibitors with Ki values of 0.87 and 3.12 μmol/L, respectively. Molecular docking experiments confirmed that the higher inhibitory potency of TTP and gAgAP might be attributed to the formation of several critical hydrogen bonds with the active site residues in ACE. We further demonstrated that TTP and gAgAP initiated a rapid and significant decrease in systolic blood pressure (SBP) in spontaneously hypertensive rats (SHRs). TTP treatment lowered SBP to the same extent as captopril, although the duration of anti-hypertensive effect was shorter in TTP group than that observed in captopril group. Moreover, the transcription levels of angiotensin II receptor type 1 (agtr1) and miR-132/-212 were downregulated in SHRs after administration of TTP and gAgAP. In particular, TTP treatment caused a comparable reduction of agtr1 levels compared to captopril treatment, while miR-132/212 expression was significantly decreased. These results showed that compound TTP might be served as a potential antihypertensive candidate.

Bioactive stability of microalgal protein hydrolysates under food processing and storage conditions

The stability of antioxidant protein hydrolysates from Spirulina sp. LEB 18 was evaluated under food processing conditions and after in vitro digestion. Protein hydrolysates with degrees of hydrolysis of 50.6% and 60% were obtained after 90 and 120 min of reaction, respectively, with Protemax 580 L. The results indicated that the antioxidant activity of protein hydrolysates was maintained following application of heat treatment (- 18 °C, 63 °C, and 100 °C). Moreover, the ability of protein hydrolysates to inhibit the 2,2-diphenyl-1-picrylhydrazyl radical was increased by nearly 25% upon exposure to acidified media (pH 4 and pH 6). In general terms, the protein hydrolysates were bioavailable after digestion with pepsin and pancreatin. This study supports the incorporation of bioactive peptides from microalgae into functional foods by demonstrating the maintenance of their biological activities in the face of food processing conditions and gastrointestinal digestion.

Solid-state fermentation as an efficient strategy for the biotransformation of lentils: enhancing their antioxidant and antidiabetic potentials

Background

Fermentation is a classic industrial process that can be applied as an efficient strategy to increase the release of bioactive compounds with antioxidant and antidiabetic activities.

Methods

This work reported the effects of solid-state fermentation (SSF) performed using strains of Aspergillus oryzae and Aspergillus niger on the antioxidant (DPPH, ABTS and FRAP) and in vitro antidiabetic (inhibition of α-amylase and α-glucosidase activities) potential of lentils.

Results

The results showed that the profiles of the biological activities of the extracts obtained from the fermented samples varied greatly with respect to both the microorganism involved and the fermentation time. The extracts obtained from the fermented lentils by A. oryzae after 72 h and by A. niger after 48 h using the FRAP assay showed the most remarkable changes in the antioxidant activity, increasing by 107 and 81%, respectively, compared to the nonfermented lentils. The lentil extracts produced by fermentation with A. niger after 48 h were able to inhibit the α-glucosidase activity by up to 90%, while a maximal inhibition of amylase (~ 75%) was achieved by the lentil extract obtained after 24 h of fermentation with A. oryzae. The content of the total phenolic compounds (TPCs) and the identification of them in lentil extracts correlated well with the improvement of the biological activities.

Conclusion

These results suggested that SSF was feasible to obtain extracts of fermented lentils with improved antioxidant and antidiabetic properties. Additionally, these results indicated that the proper choice of microorganism is crucial to direct the process for the production of compounds with specific biological activities.

Isolation and Characterization of Angiotensin Converting Enzyme Inhibitory Peptides from Peach Seed Hydrolysates: In Vivo Assessment of Antihypertensive Activity

A peptide fraction with molecular masses below 3 kDa (PSH-3 kDa) from a peach seed hydrolysate demonstrated high angiotensin converting enzyme (ACE) inhibitory activity (concentration to inhibit 50% ACE (IC₅₀) = 16.4 μg/mL) in our previous work. This work proposes a further study of this highly active fraction. RP-HPLC enabled two fractions (F3 and F4) with high inhibitory activity (IC₅₀ = 2.0 ± 0.5 and 1.2 ± 0.2 μg/mL, respectively) to be isolated. Peptide analysis by LC-Q-TOF-MS/MS using reverse-phase and hydrophilic interaction chromatography enabled 33 peptides within both fractions to be identified. Among them, peptide isoleucine-tyrosine-serine-proline-histidine (IYSPH) showed the highest capacity. The lack of cytotoxicity of peptides was demonstrated in three different cell lines (HeLa, HT-29, and HK-2). Oral administration of PSH-3 kDa fraction or peptide IYSPH caused a significant systolic blood pressure reduction (-30 mmHg) on spontaneously hypertensive rats after 3-6 h treatment.

Seed Protein of Lentils: Current Status, Progress, and Food Applications

Grain legumes are widely recognized as staple sources of dietary protein worldwide. Lentil seeds are an excellent source of plant-based proteins and represent a viable alternative to animal and soybean proteins for food processing formulations. Lentil proteins provide not only dietary amino acids but are also a source of bioactive peptides that provide health benefits. This review focuses on the current knowledge of seed protein, extraction and isolation methods, bioactive peptides, and food applications of lentil protein. Lentil is the most rapidly expanding crop for direct human consumption, and has potential for greater impact as a protein source for food processing applications. Improvements in lentil protein quality, amino acid composition, and processing fractions will enhance the nutritional quality of this rapidly expanding crop globally.

How Fermentation Affects the Antioxidant Properties of Cereals and Legumes

The major role of antioxidant compounds in preserving food shelf life, as well as providing health promoting benefits, combined with the increasing concern towards synthetic antioxidants, has led the scientific community to focus on natural antioxidants present in food matrices or resulting from microbial metabolism during fermentation. This review aims at providing a comprehensive overview of the effect of fermentation on the antioxidant compounds of vegetables, with emphasis on cereals- and legumes- derived foods. Polyphenols are the main natural antioxidants in food. However, they are often bound to cell wall, glycosylated, or in polymeric forms, which affect their bioaccessibility, yet several metabolic activities are involved in their release or conversion in more active forms. In some cases, the antioxidant properties in vitro, were also confirmed during in vivo studies. Similarly, bioactive peptides resulted from bacterial and fungal proteolysis, were also found to have ex vivo protective effect against oxidation. Fermentation also influenced the bioaccessibility of other compounds, such as vitamins and exopolysaccharides, enabling a further improvement of antioxidant activity in vitro and in vivo. The ability of fermentation to improve food antioxidant properties strictly relies on the metabolic activities of the starter used, and to further demonstrate its potential, more in vivo studies should be carried out.

Discovery and Study of Novel Antihypertensive Peptides Derived from Cassia obtusifolia Seeds

Antihypertensive peptides were screened from thermolysin hydrolysate of Cassia obtusifolia seeds (Jue Ming Zi) using two independent bioassay-guided fractionations, reversed-phase high-performance liquid chromatography (RP-HPLC), and strong cation-exchange (SCX) liquid chromatography coupled with angiotensin I-converting enzyme (ACE) inhibitory assay. The identical peptide in the most active RP-HPLC and SCX fractions was simultaneously de novo sequenced as FHAPWK with high-resolution mass spectrometry. FHAPWK (IC₅₀ = 16.83 ± 0.90 μM) was further identified as a competitive inhibitor and a true inhibitor on ACE by a Lineweaver-Burk plot and preincubation experiment, respectively. The molecular docking simulation indicated that FHAPWK could interact with several key residues of the ACE active site, which is consistent with the result of the inhibitory kinetics study. Moreover, its antihypertensive effect was demonstrated using the animal model of spontaneously hypertensive rats. It is concluded that FHAPWK is the first reported antihypertensive peptide derived from thermolysin hydrolysate of C. obtusifolia seeds.

Identification and Characterization of Gastrointestinal-Resistant Angiotensin-Converting Enzyme Inhibitory Peptides from Egg White Proteins

Egg proteins are recognized as excellent sources of bioactive peptides, such as angiotensin-converting enzyme inhibitory (ACEi) peptides. Oral administration of a thermolysin-digested egg white hydrolysate (T-EWH) caused a significant blood pressure reduction in spontaneously hypertensive rats; a further ACEi assay implied that its ACEi activity was enhanced after in vitro gastrointestinal (GI) digestion. These results indicated that T-EWH contained ACEi peptides resisting GI digestion and/or being further released during GI digestion. Therefore, the objective of this study was to identify these responsible ACEi peptides from T-EWH. The conventionally activity-guided fractionation was applied, coupled with a synchronized GI digestion throughout, during which both peptide yield and ACEi activity before and after the GI digestion were measured. Finally, six ACEi peptides (LAPYK, LKISQ, LKYAT, INKVVR, LFLIKH, and LGHWVY) with good GI resistance were identified with IC₅₀ values <20 μM, especially LKYAT (0.09 μM). The structure-activity relationship of these peptides was discussed. The discovery of GI-resistant ACEi peptides could further support the application of egg white proteins as functional food ingredients.

Antihypertensive Effect in Vivo of QAGLSPVR and Its Transepithelial Transport Through the Caco-2 Cell Monolayer

The peptide QAGLSPVR, which features high angiotensin-I-converting enzyme (ACE) inhibitory activity, was identified in our previous study. In this study, the in vivo antihypertensive effect of QAGLSPVR was evaluated. Results showed that QAGLSPVR exerts a clear antihypertensive effect on spontaneously hypertensive rats (SHRs), and the systolic and diastolic blood pressures of the rats remarkably decreased by 41.86 and 40.40 mm Hg, respectively, 3 h after peptide administration. The serum ACE activities of SHRs were determined at different times, and QAGLSPVR was found to decrease ACE activities in serum; specifically, minimal ACE activity was found 3 h after administration. QAGLSPVR could be completely absorbed by the Caco-2 cell monolayer, and its transport percentage was 3.5% after 2 h. The transport route results of QAGLSPVR showed that Gly-Sar and wortmannin exert minimal effects on the transport percentage of the peptide (p> 0.05), thus indicating that QAGLSPVR transport through the Caco-2 cell monolayer is not mediated by peptide transporter 1 or transcytosis. By contrast, cytochalasin D significantly increased QAGLSPVR transport (p< 0.05); thus, QAGLSPVR may be transported through the Caco-2 cell monolayer via the paracellular pathway.

Enzymatic soy protein hydrolysis: A tool for biofunctional food ingredient production

This work aimed to evaluate the digestive stability of the peptides previously identified from a Corolase PP soy protein hydrolysate (SPH) and to respond to the uncertainty about the merit of controlled hydrolysis. For this purpose, we applied an empirical and theoretical analysis, determining peptide sequences, oxygen radical scavenging (ORAC) and ACE inhibitory (iACE) activities, and the effect of hydrolysis on solubility. Results showed that during digestion most of SPH peptides were degraded as smaller ones. However, both SPH bioactivities improved significantly after digestion (3.9 ± 0.1 μmol TE/mg protein for ORAC and IC50 = 52 ± 4μg protein/mL for iACE) with similar values for soy protein isolate (SPI). With respect to solubility, the controlled hydrolysis considerably increased this functional property. In conclusion, the results indicated that controlled enzymatic hydrolysis of SPI with Corolase PP produced an ingredient more apt to be incorporated in certain nutritional or nutraceutical formulations.

Preparation and identification of novel inhibitory angiotensin-I-converting enzyme peptides from tilapia skin gelatin hydrolysates: inhibition kinetics and molecular docking

Tilapia skin gelatin was hydrolyzed by successive simulated gastrointestinal digestion, and the hydrolysates were further separated by transport across a Caco-2 cell monolayer. Angiotensin-I-converting enzyme inhibitory (ACEI) peptides were separated by successive chromatographic steps from the transport hydrolysates. We have identified two key ACEI peptides, namely VGLPNSR (741.4133 Da) and QAGLSPVR (826.4661 Da) with IC50 values of ACEI activity of 80.90 and 68.35 μM, respectively. Lineweaver-Burk plots indicated that the inhibitory ACE kinetics of the two peptides were noncompetitive. Molecular docking simulation showed that the two peptides could interact with the ACE site via hydrogen bonds with high binding power. However, the hydrogen bonds were not formed with the key amino acid residues in the active site of ACE. This finding was in accordance with the noncompetitive inhibition. This study established a novel approach to identify key ACEI peptides and suggested the use of tilapia peptides as functional food ingredients to prevent hypertension.

Effects of a combined intervention with a lentil protein hydrolysate and a mixed training protocol on the lipid metabolism and hepatic markers of NAFLD in Zucker rats

Metabolic syndrome is a cluster of metabolic alterations characterized by central obesity, dyslipidemia, elevated plasma glucose, insulin resistance (IR) and non-alcoholic fatty liver disease (NAFLD). In this study, a combined intervention of a lentil protein hydrolysate and a mixed training protocol was assessed in an animal experimental model of genetic obesity and metabolic syndrome. Thirty-two male obese and 32 lean Zucker rats were divided into eight different experimental groups. Rats performed a mixed exercise protocol or had a sedentary lifestyle and were administered a lentil protein hydrolysate or placebo. Daily food intake, weekly body weight gain, plasma parameters of glucose and lipid metabolisms, body composition, hepatic weight, total fat content and fatty acid profile, as well as gene expression of lipogenic and lipolytic nuclear transcription factors and their target genes were measured. Obese Zucker rats exhibited higher body and liver weight and fat content than did their lean counterparts. Such alterations were related to modifications in aerobic capacity, plasma biochemical parameters of glucose and lipid metabolisms, hepatic fatty acid profile and gene expression of nuclear transcription factors SREBP1c, PPARα, LXR and associated lipogenic and lipolytic enzymes. The interventions tested did not affect body weight gain but improved aerobic capacity, reduced hepatomegalia and steatosis associated with NAFLD and relieved the adverse effects produced by this condition in glucose and lipid metabolisms through the modulation in the expression of different genes involved in diverse metabolic pathways.

Antihypertensive Effects of Two Novel Angiotensin I-Converting Enzyme (ACE) Inhibitory Peptides from Gracilariopsis lemaneiformis (Rhodophyta) in Spontaneously Hypertensive Rats (SHRs)

A variety of biologically active products have been isolated from Gracilariopsis lemaneiformis. In the present study, two novel angiotensin-converting enzyme (ACE) inhibitory peptides, FQIN [M(O)] CILR, and TGAPCR, were screened and identified from G. lemaneiformis protein hydrolysates by LC-MS/MS. The IC50 values of FQIN [M(O)] CILR and TGAPCR were 9.64 ± 0.36 μM and 23.94 ± 0.82 μM, respectively. In the stability study, both peptides showed stabilities of pH, temperature, simulated gastrointestinal digestion, and ACE hydrolysis. The Lineweaver–Burk plot showed that the two peptides were noncompetitive inhibitors of ACE. Molecular docking simulated the intermolecular interactions of two peptides and ACE, and the two peptides formed hydrogen bonds with the active pockets of ACE. However, FQIN [M(O)] CILR was more closely linked to the active pockets of ACE, thereby exerting better ACE inhibition. Spontaneously hypertensive rats (SHRs) were studied with an oral dose of 10 mg/kg body weight. Both peptides reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP) in SHRs, of which FQIN [M(O)] CILR was able to reduce the systolic blood pressure by 34 mmHg (SBP) (p < 0.05). Therefore, FQIN [M(O)] CILR was an excellent ACE inhibitory peptide.

Identification and In Silico Prediction of Anticoagulant Peptides from the Enzymatic Hydrolysates of Mytilus edulis Proteins

Mytilus edulis is a typical marine bivalve mollusk. Many kinds of bioactive components with nutritional and pharmaceutical activities in Mytilus edulis were reported. In this study, eight different parts of Mytilus edulis tissues, i.e., the foot, byssus, pedal retractor muscle, mantle, gill, adductor muscle, viscera, and other parts, were separated and the proteins from these tissues were prepared. A total of 277 unique peptides from the hydrolysates of different proteins were identified by UPLC-Q-TOF-MS/MS, and the molecular weight distribution of the peptides in different tissues was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The bioactivity of the peptides was predicted through the Peptide Ranker database and molecular docking. Moreover, the peptides from the adductor muscle were chosen to do the active validation of anticoagulant activity. The active mechanism of three peptides from the adductor muscle, VQQELEDAEERADSAEGSLQK, RMEADIAAMQSDLDDALNGQR, and AAFLLGVNSNDLLK, were analyzed by Discovery Studio 2017, which also explained the anticoagulant activity of the hydrolysates of proteins from adductor muscle. This study optimized a screening and identification method of bioactive peptides from enzymatic hydrolysates of different tissues in Mytilus edulis.

Extracts of black garlic exhibits gastrointestinal motility effect

In this studied, extracts of black garlic on the improvement of gastrointestinal function, antioxidant activity, total polyphenols, total flavonoids and total polysaccharides were evaluated. Results showed that the black garlic n-butanol fraction extract (BA) had significantly increased effect within small intestine in vitro, while the ethyl acetate fractions had no significant effect on small intestine in vitro. Increase of 5-HT₄ content effectively stimulated the gastrointestinal peristalsis, which enhanced its gastrointestinal tract emptying, and promoted defecation. As for antioxidant activity test, the water extract was more effective in SOD activity test, DPPH radical scavenging rates, ferric reducing antioxidant power and reducing power. In addition, the water fraction was simulated by gastric acid digestion and hydrolysis, and the small intestine was isolated after acid hydrolysis (AW). It was found that the water fraction extract after acid hydrolysis did significantly improve the intestinal contraction rate. In short, extract of black garlic could effectively promote gastrointestinal motility and promote defecation. The active compounds were highly polar ingredients since water extract of black garlic exhibits most significant effect on improving gastrointestinal function.

pH-controlled fermentation in mild alkaline conditions enhances bioactive compounds and functional features of lentil to ameliorate metabolic disturbances

Lentil fermentation has a promising potential as a strategy for development of multifunctional ingredients targeting metabolic syndrome (MetS). Response surface methodology was applied to optimize lentil fermentation and study its effects on generation of peptides, soluble phenolics and bioactivities. Fermentation using Lactobacillus plantarum and Savinase® 16 L was carried out at different pH (6.5-8.5) and times (5.5-30 h). Analysis of variance was performed to evaluate linear, quadratic and interaction effects between fermentation parameters. pH positively affected peptides, soluble phenolic compounds and antioxidant activity whereas a negative impact on lipase inhibitory activity was observed (p < .0001). Time showed positive effect on proteolysis and negatively affected angiotensin I-converting enzyme inhibitory activity of fermented lentil (p < .0001). Multivariate optimization led to high levels of peptides, soluble phenolics and bioactivity of fermented lentil at pH 8.5 and 11.6 h. In conclusion, this study might contribute to the development of functional ingredients from lentil for MetS management.

Peptides Derived from Foods as Supportive Diet Components in the Prevention of Metabolic Syndrome

Metabolic syndrome (MSyn) includes physiological, biochemical, clinical, and metabolic abnormalities, leading to an increase in health problems like obesity, dyslipidemia, cardiovascular diseases, and diabetes, which contribute to an increase in mortality rate. One of the main factors having a key impact on our health is the food we consume. Thus, scientists work towards the discovery of novel bioactive compounds with therapeutic potential to address MSyn. According to scientific reports, peptides derived from food proteins exhibit bioactivities important for the prevention of MSyn diseases; that is, they regulate blood pressure and glycemia; reduce cholesterol level and body mass; and scavenge free radicals. The aim of this review is to study the potential role of peptides in the prevention of MSyn. Particularly peptides which exhibit the following activities: antihypertensive [angiotensin-converting enzyme (ACE) inhibition (EC 3.4.15.1)], antidiabetic [dipeptidyl peptidase IV (DPP-IV) (EC 3.4.14.5)/α-glucosidase (EC 3.2.1.20)/α-amylase (EC 3.2.1.1) inhibition)], cholesterol level reduction, antioxidative, and obesity prevention, were studied. If possible, special attention is paid in the review to the bioactivities of peptides that were measured in vivo. Some examples of peptides showing dual or multiple action against MSyn targets are presented. Moreover, using the database of bioactive peptide sequences (BIOPEP) we made a list of peptides serving simultaneous functions in counteracting MSyn dysfunctions. Such an approach may simplify the discovery of MSyn preventive peptides, as well as highlight some of them as potent bioactive ingredients that may be incorporated into foods. Moreover, the research strategy involving the in silico and in vitro/in vivo methodologies may be useful in the production of food protein hydrolysates supporting the treatment of MSyn dysfunctions.

Exploration of the molecular interactions between angiotensin-I-converting enzyme (ACE) and the inhibitory peptides derived from hazelnut (Corylus heterophylla Fisch.)

The mechanism of action of food-derived angiotensin-I-converting enzyme (ACE) inhibitory peptides has not been completely elucidated. In the present study, ion-exchange chromatography, gel filtration chromatography, reverse phase-high performance liquid chromatography, and liquid chromatography-electrospray ionization-tandem mass (LC-ESI-MS/MS) were employed for purifying and identifying the ACE inhibitory peptides from hazelnut. To understand the mode of action of these peptides, ACE inhibition kinetics, in vitro and in vivo bioavailability assays, active site analysis, and interaction between the inhibitory peptides and ACE were investigated. The results identified novel ACE inhibitory peptides Ala-Val-Lys-Val-Leu (AVKVL), Tyr-Leu-Val-Arg (YLVR), and Thr-Leu-Val-Gly-Arg (TLVGR) with IC₅₀ values of 73.06, 15.42, and 249.3 μM, respectively. All peptides inhibited the ACE activity via a non-competitive mode. The binding free energies of AVKVL, YLVR, and TLVGR for ACE were -3.46, -6.48, and -7.37 kcal/mol, respectively. The strong inhibition of ACE by YLVR may be attributed to the formation of cation-pi interactions.