Natural Inhibitors Of Angiotensin-converting Enzyme Research Articles

Peptide derived C. striata albumin as a natural angiotensin-converting enzyme inhibitor

As one of the most popular sources for fish albumin, Channa striata has been considered as a promising substitute for human albumin. However, scientific information regarding its genomic and proteomic is very limited, making its identification rather complicated. In this study, we aimed to isolate, characterize, and examine the bioactivity of protein and peptide derivatives of C. striata albumin. Fractionation of albumin from C. striata extract was conducted using Cohn Process and the yield was evaluated. The peptides were further produced by enzymatic hydrolysis. All these proteins were studied using tricine-SDS PAGE and tested for in vitro ACE inhibition. Dry weights of the Fraction-5, where the albumin was more abundant and purer, was 3.8 ± 2.1%. Based on tricine-SDS PAGE analysis, two bands of protein, e.g., approximately 10 and 13 kDa, were detected with highest intensity found in Fraction-5, which might be albumin of C. striata. An increasing trend of ACE inhibition by the fractions was observed, ranging from 7.09 to 22.99%. The highest ACEI activity was found in peptides from alcalase hydrolysis with molecular size <3 kDa (56.65 ± 2.32%, IC50 36.93 μg/mL). This value was also statistically significant compared with the non-hydrolyzed Fraction-5 and Parental Fraction, which were 23.48 ± 3.11% (P < 0.05) and 13.02 ± 0.68% (P < 0.01), respectively. Taken together, these findings suggest a promising potential of peptide-derived C. striata albumin for natural antihypertensive agents.

Cordyceps militaris Inhibited Angiotensin-Converting Enzyme through Molecular Interaction between Cordycepin and ACE C-Domain.

One of the most important therapeutic modalities for the management of hypertension is the inhibition of the angiotensin-converting enzyme (ACE). Cordyceps militaris has received substantial attention because to its therapeutic potential and biological value. To gather information about the antihypertensive properties of C. militaris, the ACE inhibitory activity was evaluated. An ethanolic extract of the fruiting body of C. militaris was obtained, and the extract was separated by UHPLC method with a fluorescence detector for the quantification of cordycepin and adenosine. The ethanolic extract had a considerably higher cordycepin level. Additionally, an in vitro kinetic analysis was carried out to find out how much C. militaris extract inhibited ACE. This extract exhibited non-competitive inhibition on ACE. The Ki value of the C. militaris extract against ACE was found to be 8.7 µg/mL. To the best of our knowledge, this is the first report of the analysis of a protein cavity together with molecular docking carried out to comprehend the intermolecular interactions between cordycepin and the ACE C-domain, which impact the spatial conformation of the enzyme and reduce its capacity to break down the substrate. According to a molecular docking, hydrogen bonding interactions between the chemicals and the ACE S2’ subsite are primarily responsible for cordycepin inhibition at the ACE C domain. All these findings suggest that C. militaris extract are a kind of natural ACE inhibitor, and cordycepin has the potential as an ACE inhibitor.

An exploration of angiotensin-converting enzyme (ACE) inhibitory peptides derived from gastrointestinal protease hydrolysate of milk using a modified bioassay-guided fractionation approach coupled with in silico analysis

An improved bioassay-guided fractionation was performed to effectively screen angiotensin-I converting enzyme inhibitory (ACEI) peptides from milk protein hydrolysate. The aqueous normal phase liquid chromatography, namely hydrophilic interaction liquid chromatography (HILIC), was used as a format of solid-phase extraction (SPE) short column for the first fractionation, then the HILIC-SPE fraction with the best ACEI activity (IC50 = 61.75 ± 5.74 µg/mL; IC50 = half-maximal inhibitory concentration) was obtained when eluted by 95% acetonitrile + 0.1% formic acid (fraction F1). The best HILIC-SPE fraction was further fractionated using reversed-phase (RP)-SPE short column. The best RP-SPE fraction was obtained when eluted by 20% acetonitrile + 0.1% formic acid (fraction P3) with an ACEI activity of IC50 36.22 ± 1.18 µg/mL. After the 2-step fractionation, the IC50 value of fraction P3 significantly decreased by 8.92-fold when compared with the crude hydrolysate. Several peptides were identified from fraction P3 using liquid chromatography-tandem mass spectrometry. The in silico analysis of these identified sequences based on the BIOPEP database predicted that HLPLPLL (HL-7) was the most active peptide against angiotensin-converting enzyme (ACE). The HL-7 derived from β-casein showed a potent ACEI activity (IC50 value is 16.87 ± 0.3 µM). The contents of HL-7 in the gastrointestinal protease hydrolysate and RP-SPE fraction originated from 1 mg of milk proteins were quantified using a multiple reaction monitoring mode upon liquid chromatography-tandem mass spectrometry analysis to give 19.86 ± 1.14 pg and 14,545.8 ± 572.9 pg, respectively. Besides, the kinetic study indicated that HL-7 was a competitive inhibitor and the result was rationalized using the docking simulation. The study demonstrated an efficient screening of ACEI peptides from commercially available milk powders using a simple SPE process instead of a sophisticated instrument such as HPLC. Moreover, the potent ACEI peptide HL-7 uncovered by this method could be a natural ACE inhibitor.

Carnosine and Kidney Diseases: What We Currently Know?

Carnosine (beta-alanyl-L-histidine) is an endogenously synthesised dipeptide which is present in different human tissues e.g. in the kidney. Carnosine is degraded by enzyme serum carnosinase, encoding by CNDP1 gene. Carnosine is engaged in different metabolic pathways in the kidney. It reduces the level of proinflammatory and profibrotic cytokines, inhibits advanced glycation end products' formation, moreover, it also decreases the mesangial cell proliferation. Carnosine may also serve as a scavenger of peroxyl and hydroxyl radicals and a natural angiotensin-converting enzyme inhibitor. This review summarizes the results of experimental and human studies concerning the role of carnosine in kidney diseases, particularly in chronic kidney disease, ischemia/reperfusion-induced acute renal failure, diabetic nephropathy and also drug-induced nephrotoxicity. The interplay between serum carnosine concentration and serum carnosinase activity and polymorphism in the CNDP1 gene is discussed. Carnosine has renoprotective properties. It has a promising potential for the treatment and prevention of different kidney diseases, particularly chronic kidney disease which is a global public health issue. Further studies of the role of carnosine in the kidney may offer innovative and effective strategies for the management of kidney diseases.

AN IN VITRO STUDY OF CINNAMOMUM ZEYLANICUM AS NATURAL INHIBITOR OF ANGIOTENSIN-CONVERTING ENZYME (ACE) ON SHEEP (OVIS ARIES) TISSUES

ABSTRACTObjective: The present study was aimed to find the angiotensin-converting enzyme (ACE) inhibitory activity using the methanolic extract ofCinnamomum zeylanicum (as a natural inhibitor) on sheep tissues as the enzyme source.Methods: Hippuryl-histidyl-leucine (HHL) as a substrate, tissue ACE activity was measured spectrophotometrically at 228 nm. For an incubationperiod of 30 minutes at 37°C, the linearity of ACE activity of kidney, lung, and testis enzyme was established. A known medicinal plant C. zeylanicumwas used as natural inhibitor of ACE. In this enzyme assay, inhibitory effect of methanolic extract of C. zeylanicum on kidney, lung and testicular ACEwas determined. ACE activity was confirmed by captopril, a standard inhibitor of ACE.Results: In the presence of a methanolic extract of C. zeylanicum (10:1), ACE activity was determined and this has inhibited ACE activity verysignificantly. C. zeylanicum leaves extract has reduced sheep kidney, lung, and testis ACE activity by 70.06%, 12.63%, and 20.23%, respectively.Conclusion: Significant inhibition was observed in the kidney ACE than in lung and testis ACE activity. This can propose that there may be a possiblerole in controlling blood pressure or reduction in cardiovascular diseases. Some plants with the great medicinal property may be considered aspromising sources of natural inhibitors of ACE for medicine and commercial uses. This comprehensive study may show numerous beneficial effects asa potential therapeutic agent for lowering blood pressure.Keywords: Angiotensin-converting enzyme, Natural angiotensin-converting enzyme inhibitor, Kinetic assay, Hippuryl-histidyl-leucine, Cinnamomumzeylanicum, Cardiovascular diseases.

The Use of Convallaria and Crataegus in the Treatment of Cardiac Dysfunction

Herbal medicines have been effectively used for the treatment of cardiovascular diseases for many years. Herbs such as&nbsp;Convallaria&nbsp;(Lily of the Valley) root and&nbsp;Crataegus&nbsp;(Hawthorne) have shown significant benefits as adjunctive or stand alone therapies for the treatment of cardiac disorders such as arrhythmia, mitral valve prolapse and shortness of breath.&nbsp;Convallaria&nbsp;has been used for the treatment of congestive heart failure and cardiomyopathy, whereas&nbsp;Crataegus&nbsp;contains flavonoids with anti-inflammatory, anti-oxidant and protective cardiac effects.&nbsp;Crataegus&nbsp;functions as a natural angiotensin converting enzyme inhibitor, and it is therefore beneficial for the treatment of hypertension.&nbsp;Convallaria&nbsp;and&nbsp;Crataegus&nbsp;have been used in combination with other herbal remedies such as&nbsp;Selenocereus&nbsp;(Night Blooming Cereus),&nbsp;Leonorus&nbsp;(Motherwort),&nbsp;Melissa&nbsp;(Lemon Balm),&nbsp;Lepidium&nbsp;(Maca), and&nbsp;Ginkgo&nbsp;(Ginkgo).&nbsp;Convallaria&nbsp;may interact with digoxin and should not be used during pregnancy, whereas&nbsp;Crataegus&nbsp;is a safe herb when used as indicated. Although accidental poisoning resulting from the ingestion of&nbsp;Convallaria&nbsp;has been reported, toxicity from this medicinal herb is rare because of its poor absorption and short half life. Studies have shown that at the appropriate doses,&nbsp;Convallaria&nbsp;and&nbsp;Crataegus&nbsp;are safe and effective alternative treatments for the management of cardiac dysfunction.

Carnosine, carnosinase and kidney diseases

Carnosine (beta-alanyl-L-histidine) is an endogenously synthesized dipeptide which is present in different human tissues, including the kidney. Carnosine is hydrolyzed by the enzyme carnosinase. There are two carnosinase homologues: serum secreted carnosinase and non-specific cytosolic dipeptidase, encoded by the genes CNDP1 and CNDP2 respectively and located on chromosome 18q22.3. Carnosine functions as a radical oxygen species scavenger and as a natural angiotensin converting enzyme inhibitor. Carnosine inhibits advanced glycation end product formation and reduces the synthesis of matrix proteins such as fibronectin and collagen type VI of podocytes and mesangial cells. In experimental studies it was shown that carnosine reduces the level of proinflammatory and profibrotic cytokines. It is suggested that carnosine is a naturally occurring anti-aging substance in human organisms with a beneficial effect on the cardiovascular system. This paper reports the results of studies concerning carnosine's role in kidney diseases, particularly in ischemia/reperfusion induced acute renal failure, diabetic nephropathy, gentamicin-induced nephrotoxicity and also in blood pressure regulation. The correlations between serum carnosine and serum carnosinase activity and polymorphism in the CNDP1 gene are analyzed. The role of CNDP1 gene polymorphism in the development of diabetic nephropathy and non-diabetic chronic kidney disease is discussed. Carnosine is engaged in different metabolic pathways. It has nephroprotective features. Further studies of carnosine metabolism and its biological properties, particularly those concerning the human organism, are required.

Bj-PRO-5a, a natural angiotensin-converting enzyme inhibitor, promotes vasodilatation mediated by both bradykinin B2 and M1 muscarinic acetylcholine receptors

Bradykinin-potentiating peptides (BPPs) or proline-rich oligopeptides (PROs) isolated from the venom glands of Bothrops jararaca (Bj) were the first natural inhibitors of the angiotensin-converting enzyme (ACE) described. Bj-PRO-5a (<EKWAP), a member of this structurally related peptide family, was essential for the development of captopril, the first site-directed ACE inhibitor used for the treatment of human hypertension. Nowadays, more Bj-PROs have been identified with higher ACE inhibition potency compared to Bj-PRO-5a. However, despite its modest inhibitory effect of ACE inhibition, Bj-PRO-5a reveals strong bradykinin-potentiating activity, suggesting the participation of other mechanisms for this peptide. In the present study, we have shown that Bj-PRO-5a induced nitric oxide (NO) production depended on muscarinic acetylcholine receptor M1 subtype (mAchR-M1) and bradykinin B2 receptor activation, as measured by a chemiluminescence assay using a NO analyzer. Intravital microscopy based on transillumination of mice cremaster muscle also showed that both bradykinin B2 receptor and mAchR-M1 contributed to the vasodilatation induced by Bj-PRO-5a. Moreover, Bj-PRO-5a-mediated vasodilatation was completely blocked in the presence of a NO synthase inhibitor. The importance of this work lies in the definition of novel targets for Bj-PRO-5a in addition to ACE, the structural model for captopril development.

Angiotensin-converting enzyme inhibition studies by natural leech inhibitors by capillary electrophoresis and competition assay.

A protocol to follow the processing of angiotensin I into angiotensin II by rabbit angiotensin-converting enzyme (ACE) and its inhibition by a novel natural antagonist, the leech osmoregulator factor (LORF) using capillary zonal electrophoresis is described. The experiment was carried out using the Beckman PACE system and steps were taken to determine (a) the migration profiles of angiotensin and its yielded peptides, (b) the minimal amount of angiotensin II detected, (c) the use of different electrolytes and (d) the concentration of inhibitor. We demonstrated that LORF (IPEPYVWD), a neuropeptide previously found in leech brain, is able to inhibit rabbit ACE with an IC(50) of 19.8 micro m. Interestingly, its cleavage product, IPEP exhibits an IC(50) of 11.5 micro m. A competition assay using p-benzoylglycylglycylglycine and insect ACE established that LORF and IPEP fragments are natural inhibitors for invertebrate ACE. Fifty-four percent of insect ACE activity is inhibited with 50 micro m IPEP and 35% inhibition with LORF (25 mm). Extending the peptide at both N- and C-terminus (GWEIPEPYVWDES) and the cleavage of IPEP in IP abolished the inhibitory activity of both peptides. Immunocytochemical data obtained with antisera raised against LORF and leech ACE showed a colocalization between the enzyme and its inhibitor in the same neurons. These results showed that capillary zonal electrophoresis is a useful technique for following enzymatic processes with small amounts of products and constitutes the first evidence of a natural ACE inhibitor in invertebrates.