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

Identification and Molecular Docking Analysis of Angiotensin-Converting Enzyme Inhibitors from Finger Millet (Eleusine coracana)

Hypertension remains a significant global health concern, contributing significantly to cardiovascular diseases and mortality rates. The inhibition of angiotensin-converting enzyme (ACE) plays a crucial role in alleviating high blood pressure. We investigated the potential of finger millets (Eleusine coracana) as a natural remedy for hypertension by isolating and characterizing its ACE-inhibitory compound. First, we evaluated the ACE-inhibitory activity of the finger millet ethanol extract and subsequently proceeded with solvent fractionation. Among the solvent fractions, the ethyl acetate fraction exhibited the highest ACE inhibitory activity and was further fractionated. Using preparative high-performance liquid chromatography, the ethyl acetate fraction was separated into four subfractions, with fraction 2 (F2) exhibiting the highest ACE inhibitory activity. Subsequent 1 H-nuclear magnetic resonance (NMR) and 13 C-NMR analyses confirmed that the isolated compound from F2 was catechin. Furthermore, molecular docking studies indicated that catechin has the potential to act as an ACE inhibitor. These findings suggest that finger millets, particularly as a source of catechin, have the potential to be used as a natural antihypertensive.

A traditional Korean fermented food, Gochujang exerts anti-hypertensive effects, regardless of its high salt content by regulating renin-angiotensin-aldosterone system in SD rats

The current study aimed to investigate the distinct outcomes of table salt and salt in Gochujang on blood pressure (BP). Animals were divided into 3 groups, including normal diet (NS, 0.5 % NaCl), high-salt diet (HS, normal diet with 8 % NaCl), or high-salt Gochujang diet (HSG, normal diet with Gochujang containing 8 % NaCl). Compared to the NS groups, the HS group showed significantly increased systolic blood pressure (SBP), while the HSG group did not elevate SBP. The HS group had lower serum angiotensin II and aldosterone levels than the NS group, while the HSG group showed higher levels of those parameters than the HS group. The renal mRNA expression related to the renin-angiotensin-aldosterone system (RAAS) was significantly higher in the HS group than the NS group, while the HSG group had markedly lower expression of those markers. The urinary and fecal Na+/K+ proportion was higher in both HS and HSG groups relative to the NS group, but the HSG group showed a decreased Na+/K+ ratio in urine and feces compared to the HS group. Moreover, the HS group had a significantly upregulated mRNA level of Na+/HCO3- co-transporter (Slc4a4) in the kidney than the NS group, whereas the HSG group showed downregulated mRNA expression of Slc4a4 compared to the HS group. This study demonstrates that Gochujang has anti-hypertensive effects regardless of its high salt content and provide the evidence regarding the distinct impacts between salt in Gochujang and the table salt.

In silico and in vivo experiment of soymilk peptide (tetrapeptide - FFYY) for the treatment of hypertension

Enzyme-Treated Soymilk (ETS) was produced from Commercial Soymilk (CSM) with the treatment of proteinase PROTIN SD-NY10 (Bacillus amyloliquefaciens). Previously, we have isolated novel peptides from ETS but data related to isolated-peptides are scant. In this study, bio-informatics and in vivo analysis of isolated-peptides showed strong binding affinity to the active site of the Angiotensin Converting Enzyme (ACE). Among four peptides, tetrapeptide Phe-Phe-Tyr-Tyr (FFYY) showed strong binding affinity and inhibitory activity to the ACE-enzyme (binding affinity -9.5 Kcal/mol and inhibitory concentration of 1.9 µM respectively) as well as showed less toxicity compared to other peptides. The animal experiment revealed that single oral dose of FFYY (80 µg/kg body weight/day) effectively ameliorates the systolic, diastolic and mean blood pressure in the spontaneously hypertensive rat (SHR) model. Chronic oral administration of FFYY (80 µg/kg body weight/day for 3 weeks) reduced the systolic blood pressure elevation and ACE activity without any adverse side effects on the physiological and biological parameters of SHR. In conclusion, both in silico and in vivo experiments of soymilk-isolated FFYY peptide showed a promising option as a potential alternative for hypertension treatment without adverse side effects on SHR.

Screening and Constructing of Novel Angiotensin I-Converting Enzyme Inhibiting Peptides from Walnut Protein Isolate and Their Mechanisms of Action: A Merged In Silico and In Vitro Study

Angiotensin I-converting enzyme (ACE)-inhibiting peptides were isolated from walnut protein isolate (WPI) using ultrasound-assisted extraction. This study aimed to assess the impact of ultrasonic pretreatment on the physicochemical properties of WPI. The optimal extraction conditions for WPI were determined as a 15-min ultrasonic treatment at 400 W. Subsequently, the hydrolysate exhibiting the highest in vitro ACE-inhibiting activity underwent further processing and separation steps, including ultrafiltration, ion exchange chromatography, liquid chromatography-tandem mass spectrometry, ADMET screening, and molecular docking. As a result of this comprehensive process, two previously unidentified ACE-inhibiting peptides, namely Tyr-Ile-Gln (YIQ) and Ile-Tyr-Gln (IYQ), were identified. In addition, a novel peptide, Ile-Lys-Gln (IKQ), was synthesized, demonstrating superior ACE-inhibiting activity and temperature stability. In silico analysis estimated an in vivo utilization rate of 21.7% for IKQ. These peptides were observed to inhibit ACE through an anti-competitive mechanism, with molecular docking simulations suggesting an interaction mechanism involving hydrogen bonding. Notably, both IYQ and IKQ peptides exhibited no discernible toxicity to HUVECs cells and promoted nitric oxide (NO) generation. These findings underscore the potential of ultrasonicated WPI in the separation of ACE-inhibiting peptides and their utility in the development of novel ACE inhibitors for functional food applications.

Structure Characterization and Antihypertensive Effect of an Antioxidant Peptide Purified from Alcalase Hydrolysate of Velvet Antler

Recently, interest in food-derived bioactive peptides as promising ingredients for the prevention and improvement of hypertension is increasing. The purpose of this study was to determine the structure and antihypertensive effect of an antioxidant peptide purified from velvet antler in a previous study and evaluate its potential as a various bioactive peptide. Molecular weight (MW) and amino acid sequences of the purified peptide were determined by quadrupole time-of-flight electrospray ionization mass spectroscopy. The angiotensin I-converting enzyme (ACE) inhibition activity of the purified peptide was assessed by enzyme reaction methods and in silico molecular docking analysis to determine the interaction between the purified peptide and ACE. Also, antihypertensive effect of the purified peptide in spontaneously hypertensive rats (SHRs) was investigated. The purified antioxidant peptide was identified to be a pentapeptide Asp-Asn-Arg-Tyr-Tyr with a MW of 730.31 Da. This pentapeptide showed potent inhibition activity against ACE (IC₅₀ value, 3.72 μM). Molecular docking studies revealed a good and stable binding affinity between purified peptide and ACE and indicated that the purified peptide could interact with HOH2570, ARG522, ARG124, GLU143, HIS387, TRP357, and GLU403 residues of ACE. Furthermore, oral administration of the pentapeptide significantly reduced blood pressure in SHRs. The pentapeptide derived from enzymatic hydrolysate of velvet antler is an excellent ACE inhibitor. It might be effectively applied as an animal-based functional food ingredient.

Novel angiotensin I-converting enzyme (ACE) inhibitory peptides from walnut protein isolate: Separation, identification and molecular docking study

Walnut protein isolate was hydrolyzed using alcalase® to obtain angiotensin-I-converting enzyme (ACE) inhibitory (ACEI) peptides. The components with high ACEI activity were successfully purified from walnut protein isolate hydrolysates (WPIH) by ultrafiltration and G-25 gel chromatography. The 1520 peptides were identified by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Then the screening model of ACEI peptides was established by in silico approach. It was found that four ACEI active peptides (PPKP, YPQY, YLPP, and PKPP) were obtained with IC₅₀ values ranging from 506 to 89 μmol/L, among which PPKP had the highest ACEI activity (IC₅₀  = 89 ± 1 μmol/L). The four peptides mentioned above were novel, non-toxic, and resistant to gastrointestinal digestion. The molecular docking studies showed that the ACEI effect of ACEI peptide was mainly due to the interaction with residues of Gln281 and His353 in the ACE active pockets. In vivo availability of ACEI peptides showed that the probability of PPKP binding to ACE was 37.9% in the human body. Our studies suggest that the ACEI peptides derived from the WPIH can be considered functional foods that can prevent hypertension. PRACTICAL APPLICATIONS: Hypertension is a significant risk factor for cardiovascular and cerebrovascular disease, the leading cause of death worldwide. This study used a cost-effective method to isolate and identify potential ACEI peptides from the walnut meal. Since the walnut meal is often discarded in the processing of walnut products and thus pollutes the environment, the preparation of walnut meal into ACEI peptides can reduce the impact of hypertension on people and reduce environmental pollution. The experimental results show that walnut ACEI peptides are a safe and healthy nutritional product.

Bioactive Peptides: An Understanding from Current Screening Methodology

Bioactive peptides with high potency against numerous human disorders have been regarded as a promising therapy in disease control. These peptides could be released from various dietary protein sources through hydrolysis processing using physical conditions, chemical agents, microbial fermentation, or enzymatic digestions. Considering the diversity of the original proteins and the complexity of the multiple structural peptides that existed in the hydrolysis mixture, the screening of bioactive peptides will be a challenge task. Well-organized and well-designed methods are necessarily required to enhance the efficiency of studying the potential peptides. This article, hence, provides an overview of bioactive peptides with an emphasis on the current strategy used for screening and characterization methods. Moreover, the understanding of the biological activities of peptides, mechanism inhibitions, and the interaction of the complex of peptide–enzyme is commonly evaluated using specific in vitro assays and molecular docking analysis.

Purification of Angiotensin-Converting Enzyme (ACE) from Sheep Kidney and Inhibition Effect of Reduced Nicotinamide Adenine Dinucleotide (NADH) on Purified ACE Activity

Angiotensin-converting enzyme (ACE, EC 3.4.15.1) is a significant enzyme that regulates blood pressure. ACE inhibitors are often used in the treatment of hypertension. In this work, ACE was purified and characterized in one step with affinity chromatography from sheep kidneys. ACE was 10305-fold purified and specific activity was 19,075 EU/mg protein. The molecular weight and purity of ACE were found with SDS-PAGE and observed two bands at about 60 kDa and 70 kDa on the gel. The effects of reduced nicotinamide adenine dinucleotide (NADH), an antioxidant compound, on purified ACE activity were also researched. NADH on ACE activity showed an inhibition effect. The inhibition type of NADH was determined to be non-competitive inhibition by the Lineweaver-Burk chart and IC₅₀ and K_i values for NADH were 244.33 and 175.08 µM, respectively. These results suggest that antioxidant substances might be efficient in preventing hypertension.

Novel Angiotensin-I Converting Enzyme Inhibitory Peptides Isolated From Rice Wine Lees: Purification, Characterization, and Structure-Activity Relationship

The bioactive peptides that can inhibit angiotensin-I converting enzyme (ACE, EC. 3. 4.15.1) are considered as possible cures of hypertension. Food-derived angiotensin-I converting enzyme inhibitory (ACEi) peptides have gained more attention because of their reduced side effects. In this study, we reported the method for purifying ACEi peptides from the lees of traditional Chinese rice wine and evaluated the product's biochemical properties. After three steps of reversed-phase high-performance liquid chromatography (RP-HPLC), for the first time, we isolated, purified, and identified two novel peptides: LIIPQH and LIIPEH, both of which showed strong ACEi activity (IC₅₀-values of 120.10 ± 9.31 and 60.49±5.78 μg/ml, respectively). They were further categorized as mixed-type ACE inhibitors and were stable against both ACE and gastrointestinal enzymes during in vitro digestion. Together, these results suggest that the rice wine lees that produced as a by-product during rice wine production can be utilized in various fields related to functional foods and antihypertensive medicine.

Identification and Characterization of Edible Cricket Peptides on Hypertensive and Glycemic In Vitro Inhibition and Their Anti-Inflammatory Activity on RAW 264.7 Macrophage Cells

Recent studies continue to demonstrate the potential of edible insects as a protein base to obtain bioactive peptides applicable for functional food development. This study aimed at identifying antihypertensive, anti-glycemic, and anti-inflammatory peptides derived from the in vitro gastrointestinal digests of cricket protein hydrolysates. After sequential fractionation, the protein digest subfraction containing the lowest molecular weight (<0.5 kDa), hydrophobic (C18) and cationic peptides (IEX) was found responsible for the most bioactivity. The cationic peptide fraction significantly reduced (p < 0.05) α-amylase, α-glucosidase, and angiotensin converting enzyme (ACE) activity in vitro, and also inhibited the expression of NF-κB in RAW 264.7 macrophage cells. A total of 28 peptides were identified with mass spectrometry (LC–MS/MS) and de novo sequencing from the potent fraction. Three novel peptides YKPRP, PHGAP, and VGPPQ were chosen for the molecular docking studies. PHGAP and VGPPQ exhibited a higher degree of non-covalent interactions with the enzyme active site residues and binding energies comparable to captopril. Results from this study demonstrate the bioactive potential of edible cricket peptides, especially as ACE inhibitors.

Physicochemical characterisation, molecular docking, and drug-likeness evaluation of hypotensive peptides encrypted in flaxseed proteome

In this study, hypotensive peptides derived from mature flaxseed protein sequences were predicted in silico using BIOPEP-UWM with nine proteases, three each from digestive, plant and microbial sources. The physicochemical properties of 2256 ACE-inhibitory peptides and 267 renin-inhibitory peptides (including seven (7) peptides with dual inhibitory activities against both ACE and renin enzymes) were assessed in silico using the ‘Peptides’ package of R. The hypotensive peptides showed relatively low molecular weight (mol. wt.) range (132 = mol. wt. ≤ 442 Da); broad range of isoelectric point (3.61 = pI ≤ 12.50); both high (>2) and low (≤2) Boman indices, and a variety of hydrophobicity indices (hydrophilic, hydrophobic and amphipathic properties). Following this, the seven peptides with dual ACE and renin inhibitory activities were selected for molecular docking with the respective enzyme receptors. The binding energies of the seven hypotensive peptides with ACE and renin respectively ranged from −36.82 to −25.94 kJ/mol, and −33.05 to −27.61 kJ/mol; and compared well with values recorded for inhibitor drugs, captopril (−26.78 kJ/mol) and aliskiren (−34.73 kJ/mol). The seven peptides inhibited ACE through hydrogen bonds, electrostatic and hydrophobic interactions; and renin, mainly through hydrogen bonds and hydrophobic interactions. In silico prediction of adsorption, digestion, metabolism, excretion and toxicity (ADME/Tox) profile based on physicochemical properties and Lipinski's rule-of-five showed that the peptides were non-toxic and had desirable drug-like properties (flexibility, lipophilicity, molecular weight, gastrointestinal absorption, and bioavailability). This study provides insight into the molecular interactions of hypotensive peptides with their physiological targets, and the potential to develop the bioactive peptides from flaxseed proteins.

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Flaxseed proteins were assessed in silico as source of hypotensive peptides.

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Plant proteases were most suitable to release hypotensive peptides in silico.

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Hypotensive peptides had molecular docking features similar to captopril and aliskiren.

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In silico-derived hypotensive

peptides were non-toxic, and had drug-like properties.

Antihypertensive Effects of Virgin Olive Oil (Unfiltered) Low Molecular Weight Peptides with ACE Inhibitory Activity in Spontaneously Hypertensive Rats

The low molecular weight peptide composition of virgin olive oil (VOO) is mostly unknown. We hypothesised that unfiltered VOO could possess low molecular weight peptides with antihypertensive activity. We produced unfiltered VOO and obtained a water-soluble peptide extract from it. The peptides were separated by size-exclusion using fast protein liquid chromatography, and the low molecular weight fraction was analysed by nanoscale liquid chromatography-Orbitrap coupled with tandem mass spectrometry and de novo sequencing. We selected 23 peptide sequences containing between 6 and 9 amino acids and molecular masses ranging 698–1017 Da. Those peptides were chemically synthesised and their angiotensin-converting enzyme (ACE) inhibitory activity was studied in vitro. Seven peptides showed a strong activity, with half maximal inhibitory concentration (IC50) <10 µm. The antihypertensive effects of the four most active synthesised ACE inhibitor peptides were studied in spontaneously hypertensive rats (SHR). Acute oral administration of synthetic peptides RDGGYCC and CCGNAVPQ showed antihypertensive activity in SHR. We conclude that unfiltered VOO naturally contains low molecular weight peptides with specific ACE inhibitory activity and antihypertensive effects in SHR.