Angiotensin I-converting Enzyme Inhibitor Research Articles

In vitro anti-hypertensive activity of Jasminum grandiflorum subsp. floribundum (Oleaceae) in relation to its metabolite profile as revealed via UPLC-HRMS analysis

Jasminum is an important genus in the olive family (Oleaceae), comprising about 200 species distributed all over the world. In the current study, the methanolic extract of Jasminum grandiflorum subsp. floribundum aerial parts and its respective fractions; dichloromethane and n-butanol fractions were analyzed using ultra-performance liquid chromatography coupled to high resolution mass (UPLC-HRMS) for profiling and characterization of the plant metabolites. More than seventy metabolites were identified belonging to different classes including phenolic acids, flavonoids, secoiridoids, iridoids, lignans, fatty acids, and triterpenes. The samples were also assessed for their angiotensin-I-converting enzyme (ACE) and renin inhibitory activity along with their antioxidant potential using five complementary assays: TAC (total antioxidant capacity), DPPH (1,1-diphenyl-2-picrylhydrazyl), ABTS (2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid), FRAP (ferric reducing antioxidant power) and iron reducing power. The results revealed that the n-butanol fraction showed a potent ACE and renin inhibition as compared to Lisinopril and Aliskiren standard drugs (24.66 ± 2.41 ng/mL vs. 18.37 ± 1.21 ng/mL and 141.14 ± 5.28 ng/mL vs. 447.87 ± 3.2 ng/mL, respectively) and also a strong antioxidant activity. Interestingly, the secoiridoids, dominated metabolites detected in the n-butanol fraction, revealed the potential of them for management of the hypertension diseases. The total extract and fractions were also standardized using HPLC analysis of the major secoiridoid glycoside; oleuropein. Finally, J. grandiflorum standardized extract could be considered as a target for further studies to discover a new therapeutic anti-hypertensive drug.

Nicotianamine-rich foods for improving the learning and memory functions and as an effective preventing agent of hypertension

Hypertension is considered one of the most serious long-term medical conditions. Angiotensin I-converting enzyme (ACE), as one of the most important targets for hypertension drugs. It converts angiotensin I to vasopressor angiotensin II through a catalytic hydrolysis process. ACE has been found in higher amounts in the brain cells of Alzheimer disease patients. Brain-penetrating ACE inhibitors (ACEI) decreased the impact of Alzheimer disease in elderly hypertensive patients. It is expected that the inclusion of ACEI-rich foods has a potential to eliminate these health issues. Therefore, this study explored the occurrence of ACEI in food extracts combining an ACE inhibition assay with LC/ESIMS quantification analysis, showing that naturally occurring nicotianamine (NA), ubiquitously present in higher plants, is an important constituent in ACEI active foods. Furthermore, oral administration of NA and NA-rich food extracts improved spatial learning and memory functions in rats, in addition to hypertensive relief. Thus, NA is suggested to be a brain-penetrating ACEI, while the inclusion of NA-rich foods will contribute to the “quality of life” of patients with Alzheimer disease by relieving hypertension and dementia.

In Vitro Modeling of Bradykinin-Mediated Angioedema States.

Kinins (peptides related to bradykinin, BK) are formed from circulating substrates, the kininogens, by the action of two proteases, the kallikreins. The only clinical application of a BK receptor ligand, the B2 receptor antagonist icatibant, is the treatment of the rare hereditary angioedema (HAE) caused by the deficiency of C1-esterase inhibitor (C1-INH). Less common forms of HAE (genetic variants of factor XII, plasminogen, kininogen) are presumably mediated by increased BK formation. Acquired forms of BK-mediated angioedema, such as that associated with angiotensin-I converting enzyme (ACE) inhibition, are also known. Antibody-based analytical techniques are briefly reviewed, and support that kinins are extremely short-lived, prominently cleared by ACE. Despite evidence of continuous activation of the kallikrein–kinin system in HAE, patients are not symptomatic most of the time and their blood or plasma obtained during remission does not generate excessive immunoreactive BK (iBK), suggesting effective homeostatic mechanisms. HAE-C1-INH and HAE-FXII plasmas are both hyperresponsive to fibrinolysis activation. On another hand, we suggested a role for the alternate tissue kallikrein–kinin system in patients with a plasminogen mutation. The role of the BK B1 receptor is still uncertain in angioedema states. iBK profiles under in vitro stimulation provide fresh insight into the physiopathology of angioedema.

A comparative study of compositional, antioxidant capacity, ACE-inhibition activity, RP-HPLC peptide profile and volatile compounds of herbal artisanal cheeses

The effect of aromatic herbs on the RP-HPLC peptide profile, angiotensin I-converting enzyme-inhibitory (ACE-i) activity, antioxidant capacity and volatile compounds in artisanal cheeses was investigated. Three representative artisanal cheeses (white brined, beaten and Kashkaval cheeses) were produced using aromatic herbs (Mentha longifolia, Origanum vulgare, Thymus longicaulis, Alium sativum, Petroselinum crispum, Capsicum annuum). Compared with control group, herbal cheeses (except white cheese with garlic and parsley) revealed a significant increase in antioxidant activity. The highest ACE-i activity was noticed in 60 days of ripening with a mean value of 98.72% in goat beaten cheese and 97.78% in Kashkaval cheese enriched with peppers. One hundred and one volatile compounds, mainly acids, esters and alcohols, were identified in significantly higher amounts in cheeses made with herbs and contributed to the development of the overall aroma perception.

Comparative Study of Angiotensin I-Converting Enzyme (ACE) Inhibition of Soy Foods as Affected by Processing Methods and Protein Isolation

Angiotensin converting enzyme (ACE) converts angiotensin I into the vasoconstrictor angiotensin II and eventually elevates blood pressure. High blood pressure is a major risk factor for heart disease and stroke. Studies show peptides present anti-hypertensive activity by ACE inhibition. During food processing and digestion, food proteins may be hydrolyzed and release peptides. Our objective was to determine and compare the ACE inhibitory potential of fermented and non-fermented soy foods and isolated 7S and 11S protein fractions. Soy foods (e.g., soybean, natto, tempeh, yogurt, soymilk, tofu, soy-sprouts) and isolated proteins were in vitro digested prior to the determination of ACE inhibitory activity. Peptide molecular weight distribution in digested samples was analyzed and correlated with ACE inhibitory capacity. Raw and cooked soymilk showed the highest ACE inhibitory potential. Bacteria-fermented soy foods had higher ACE inhibitory activity than fungus-fermented soy food, and 3 day germinated sprouts had higher ACE inhibition than those germinated for 5 and 7 days. The 11S hydrolysates showed higher ACE inhibitory capacity than 7S. Peptides of 1–4.5 kDa showed a higher contribution to reducing IC50. This study provides evidence that soy foods and isolated 7S and 11S proteins may be used as functional foods or ingredients to prevent or control hypertension.

Development and Characterization of Orally Disintegrating Tablets Containing a Captopril-Cyclodextrin Complex.

Captopril is the first angiotensin I-converting enzyme inhibitor widely used for the treatment of hypertension. Based on the well-known benefits of cyclodextrin inclusion complexes, the present study investigated the ability of β-cyclodextrin to include captopril. Solid inclusion complexes of captopril with β–cyclodextrin in a 1:2 molar ratio were prepared by using the paste method of complexation. For comparison purposes, a simple physical mixture with the same molar ratio was also prepared. Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and simultaneous thermal analysis were used to characterize the raw materials, physical mixture and solid inclusion complex. In order to provide the drug in a more accessible and patient-compliant form following masking its bitter taste, as well as ensuring the appropriate release kinetics, the investigated complex was formulated as orally disintegrating tablets. The study of captopril dissolution in both compendial and simulated saliva media suggested the Noyes Whitney model as the best mathematical model to describe the release phenomena. A clinical study on healthy volunteers also highlighted the taste improvement of the new formulation as compared to conventional tablets.

Production and characterization of chicken blood hydrolysate with antihypertensive properties

Chicken blood has limited utilization despite its high protein content. Production of a blood hydrolysate exhibiting angiotensin I-converting enzyme (ACE)–inhibitory activity would be means of valorizing chicken blood. The optimized conditions used to produce chicken blood corpuscle hydrolysate (BCH) by Alcalase were 51.1°C, 4% enzyme, and pH 9.6 for 6 h, resulting in a 35.8% degree of hydrolysis and 37.7% ACE inhibition at a peptide concentration of 0.2 mg/mL. The permeate of a 1-kDa membrane, BCH-III, showed a 2.5-fold increase in ACE inhibition compared with that of BCH. BCH-III was resistant to in vitro gastrointestinal digestion, whereas the BCH digesta exhibited an increased ACE-inhibitory activity after digestion. Both BCH and BCH-III were rich in hydrophobic amino acids. A single administration of BCH and BCH-III to spontaneously hypertensive rats at concentrations of 600 and 100 mg/kg, respectively, lowered the systolic blood pressure by −57.7 and −70.9 mmHg, respectively, 6 h after oral administration compared with the control group. The blood pressure–lowering effect of the 600 mg/kg BCH dose was comparable with that of the 100 mg/kg BCH-III dose after 4 wk of oral administration. Both BCH and BCH-III could be developed for use as nutraceutical products with antihypertensive effects.

Hydrolysates from tuna cooking juice as an anti-hypertensive agent

Tuna cooking juice containing 4% protein was hydrolyzed using a commercial protease, Orientase from Bacillus subtilis, to prepare hydrolysate (OAH) that inhibits angiotensin I-converting enzyme (ACE). The systolic blood pressure (SBP) dropped by 18 mmHg in spontaneously hypertensive rats (SHR) 2hr after being orally administered the hydrolysate at 0.25g hydrolysate/kg body weight, and reduced, from 172 mmHg to 150 and 142 mmHg for those administered with lyophilized OAH at 0.5 and 1.0 g/kg body weight, respectively. This indicated that the lowering effect on SBP was dose-dependent. Constituents derived from the gel filtration of OAH with molecular weight ranging from 240-565 Da exerted an obvious effect on SBP. Although the reduced SBP in SHR gradually returned to the original level, the reduction effect lasted for 2-10 hr, depending on the dose. The SBP of SHR fed on a normal diet increased gradually to 215 mmHg by the age of 15 weeks, while it decreased, then increased to and stayed at, respectively, 200, 205 and 215 mmHg for those fed on diets containing 2.5, 1.25 or 0.25% lyophilized OAH. This result showed that proteins in tuna cooking juice are potential source of ACE-inhibiting agent, and thus may be useful to regulate the blood pressure.

Angiotensin I-converting enzyme inhibitory activity of protein hydrolysates from tuna broth

Angiotensin I-converting enzyme (ACE) inhibitors have a potent antihypertensive effect in both humans and animals. Various peptides derived from food proteins were found to have ACE inhibitory activity. For determining ACE inhibitory activity, protein hydrolysates were prepared from tuna broth (contain 4% water-soluble protein) using various commercial proteases. Orientase hydrolysate (OAH) exhibited the most potent inhibitory activity on ACE. The best hydrolysis conditions with respect to inhibition of ACE were 3hr of incubation at 50°C, pH 6.5, with enzyme (1.0% orientase) to substrate (tuna broth) of 1/25 (v/v). Preparation under these conditions yielded activity (IC50 12.52 ± 0.02 mg/mL). Fractionation of the orientase, hydrolysate on a Sephadex G-25 gel filtration chromatograph resulted in the production of more active inhibitors. The active fractions were peptides of molecular weights < 1,000 Da. The most active fraction had an IC50 value of 0.21 ± 0.01 mg/mL. This fraction was rich in basic amino acids and aromatic amino acids [peptides with molecular mass (< 565 Da)].

One peptide derived from hen ovotransferrin as pro-drug to inhibit angiotensin converting enzyme

Angiotensin I-converting enzyme (ACE) inhibitory peptide was derived from hen ovotransferrin and identified as Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr. It produced a concentration-dependent inhibition of ACE activity in vitro with an IC50 value of 102.8 μM. After hydrolysis by ACE, the product (Lys-Val-Arg-Glu-Gly-Thr) has an IC50 value of 9.1 μM that was about 11-fold lower of the parent peptide. Thus, Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr can be considered as a pro-drug. Moreover, Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr and Lys-Val-Arg-Glu-Gly-Thr were intravenously administered into spontaneously hypertensive rats (SHR) to monitor the time-course change of systolic blood pressure. We found that Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr and its hydrolyzed product produced the maximal reduction of systolic blood pressure at 40 min and 20 min after injection, respectively. This 20 min delay might be considered as the time required for conversion of prodrug into Lys-Val-Arg-Glu-Gly-Thr, the true ACE inhibitor. In conclusion, the obtained results suggest that Lys-Val-Arg-Glu-Gly-Thr-Thr-Tyr works as the pro-drug of Lys-Val-Arg-Glu-Gly-Thr to inhibit ACE activity in vivo.

Production of angiotensin I-converting enzyme inhibitor derived from egg white protein hydrolysates using a membrane reactor

Egg white proteins (EWP) were hydrolyzed with four proteolytic enzymes, including Thermolysin, Alcalase, Esperase and Chymotrysin, to produce hydrolysates with angiotensin I-converting enzyme (ACE) inhibitory activity. The result indicated that EWP hydrolyzed for 0.5-24 hr with Thermolysin produced the highest ACE inhibitory activity among the four enzymes. Therefore, EWP-Thermolysin hydrolysate was produced and further fractionated using several membranes with molecular weight cut-off (MWCO) of 10,000, 3,000 and 1,000 daltons, sequentially. The 1 kDa permeate obtained from the hydrolysate treatment using 1,000 daltons MWCO membrane could further reduce its IC50 value from 54.1 to 17.2 μg protein/mL. A lower IC50 value represented higher ACE inhibitory activity. The operation stability study showed that the membrane reactor system could maintain a steady production of EWP-Thermolysin hydrolysate over 8 hr. The gastrointestinal protease in vitro effect on the ACE inhibitory activity of 1 kDa permeate indicated that gastrointestinal proteases have no significant effect (p＞0.05) on the ACE inhibitory activity of 1 kDa permeate.

In vitro antioxidant and angiotensin I-converting enzyme inhibitory properties of peptides derived from corn gluten meal

Corn gluten meal (CGM) was hydrolyzed by Alcalase 2.4L and Protex 7L to obtain low-molecular-weight peptides. The antioxidant and angiotensin-I-converting enzyme (ACE) inhibitory activities of the peptides were determined by 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radical scavenging activity, the JHH7 cell oxidative stress model, and the ACE inhibition assay, respectively. Corn peptides (CPs) had strong antioxidant capacity to scavenge ABTS radicals (1.44 ± 0.11 mmol/g), and significantly reduced reactive oxygen species and malondialdehyde levels in oxidized JHH7 cells, increasing superoxide dismutase, catalase, and glutathione peroxidase activities by 26.20%, 147.52%, and 43.20%, respectively, at the concentration of 800 μg/mL. CPs had high ACE inhibitory activity, with an IC50 value of 0.27 ± 0.05 mg/mL. Next, the CPs were separated by reverse-phase high-performance liquid chromatography. Twelve fractions were collected, and their ABTS free radical scavenging and ACE inhibitory activities were determined. Fractions 1, 2, 3, 4, and 9 showed higher ABTS free radical scavenging and ACE inhibitory activities. Twelve peptides were identified from active fractions by liquid chromatography–tandem mass spectrometry (LC–MS/MS) as Leu-Ser-Pro-Tyr, Leu-Asn-Ser-Pro-Ala-Tyr, Tyr-Gly-Pro-Gln, Pro-Pro-Tyr, Ala-Tyr-Pro-Glu, Thr-Tyr-Ser-Gly-Pro-Lys, Ala-Tyr-Pro-Gly-Pro-Gln, Leu-Ala-Tyr-Pro-Gln, Ala-Tyr-Leu-Gln-Gln-Gln, Ser-Ala-Pro, Asn-Ala-Pro, and Val-Asn-Ala-Pro. These peptides exhibited good ABTS free radical scavenging and ACE inhibitory activities. Therefore, CPs may have potential applications in the food industry as functional material additives.

Bioactive Protein Hydrolysate Obtained from Canned Sardine and Brewing By-products: Impact of Gastrointestinal Digestion and Transepithelial Absorption

A sardine protein hydrolysate (SPH) was prepared by hydrolysis of sarcoplasmic proteins from canned sardine by-product with proteases from brewer’s spent yeast (BSY). The SPH presented in vitro angiotensin converting enzyme-inhibitory (ACE-I) and ferric reducing antioxidant potential (FRAP). However, the challenge before in vivo efficacy studies is to understand the impact of ultrafiltration (UF), simulated gastrointestinal (GI) digestion, and the intestinal cell permeability. Thus, this work was carried out to study the influence of these parameters on SPH bioactivity; two predictive models for human intestinal absorption were compared. Results showed that ACE-I and antioxidant activities were improved after UF of SPH through a 10 kDa cut-off membrane; simulated GI increased the FRAP value whereas the ACE-I remained similar. The apparent permeability coefficients of < 10 kDa fraction evaluated using Caco-2 and Caco-2/HT29-MTX cell models were 5.89 × 10−6 cm/s and 10.93 × 10−6 cm/s, respectively. Mass spectrometry revealed that molecules with m/z between 1000 and 5000 were transported across Caco-2/HT29-MTX cell monolayer. Basolateral permeates presented antioxidant activity but no ACE-I activity was detected. These results suggest that SPH prepared by BSY proteases is promising as functional ingredient with enhanced antioxidant activity and justifies further in vivo studies to confirm its pharmacological efficacy.

Production of an antihypertensive peptide from milk by the brown rot fungus Neolentinus lepideus

Fermented milk has been shown to have beneficial effects on human health exerted through its bioactive peptides. The lactose-fermenting brown rot fungus Neolentinus lepideus has been shown to ferment milk; however, its ability to produce bioactive peptides has not been explored. This study, therefore, aimed to investigate the ability N. lepideus for the production of antihypertensive peptides in fermented milk and to characterize the peptides. Here we have used 9% skim milk as the substrate and fermented it with the mycelia of N. lepideus. The fermented milk exhibited higher angiotensin I-converting enzyme (ACE) inhibitory activity as compared to the commercially available sour milk containing Ile-Pro-Pro and Val-Pro-Pro. As a result of isolation and purification by reverse-phase high-performance liquid chromatography, followed by peptide sequencing and MS analysis, the dipeptide Tyr-Pro (YP) was identified as an active peptide. The concentration of YP in the fermented milk reached up to 450 μg/ml, which was > twofold higher than the IC50 for ACE inhibition. Subsequently, the antihypertensive effect of YP was validated through intravenous injection of the peptide, which exhibited a significant lowering of blood pressure in a rat model of genetic hypertension. In addition, the transcriptomic analysis revealed the probable role of the carboxypeptidases for the increased yield of YP. These results together indicated that the fermentation with basidiomycete fungus could be a viable approach to produce bioactive peptides, and may, therefore, be applicable in the development of a cost-effective mass production system for functional peptides.

Current genetic engineering strategies for the production of antihypertensive ACEI peptides.

Hypertension is a major and highly prevalent risk factor for various diseases. Among the most frequently prescribed antihypertensive first-line drugs are synthetic angiotensin I-converting enzyme inhibitors (ACEI). However, since their use in hypertension therapy has been linked to various side effects, interest in the application of food-derived ACEI peptides (ACEIp) as antihypertensive agents is rapidly growing. Although promising, the industrial production of ACEIp through conventional methods such as chemical synthesis or enzymatic hydrolysis of food proteins has beenproven troublesome. We here provide an overview ofcurrent antihypertensive therapeutics, focusing on ACEI, and illustrate how biotechnology and bioengineering can overcome the limitations ofACEIp large-scale production. Latest advances in ACEIp research and current genetic engineering-based strategies for heterologous production of ACEIp (and precursors) are also presented. Cloning approaches include tandem repeats of single ACEIp, ACEIp fusion to proteins/polypeptides, joining multivariate ACEIp into bioactive polypeptides, and producing ACEIp-containing modified plant storage proteins. Although bacteria have been privileged ACEIp heterologous hosts, particularly when testing for new genetic engineering strategies, plants and microalgae-based platforms are now emerging. Besides being generally safer, cost-effective and scalable, these "pharming" platforms can perform therelevant posttranslational modifications and produce (and eventually deliver) biologically active protein/peptide-based antihypertensive medicines.

Effect of simulated gastrointestinal digestion of bioactive peptide from pigeon pea (Cajanus cajan) tempe on angiotensin-I converting enzyme inhibitory activity

Purpose The purpose of this paper is to understand the effect of hydrolysis by pepsin and pancreatin on the angiotensin-I-converting enzyme (ACE) inhibitory activity of bioactive peptide from pigeon pea tempe and the absorption of pigeon pea tempe peptide by using the everted gut sac method. Design/methodology/approach The tempe was prepared by inoculating Raprima (Rhizopus oligosporus) on hulled-cooked pigeon pea for 48 h. The extraction was performed using the ultrasonic method at 40 kHz frequency and 100% ultrasonic power for 10 min. The extracted protein was placed in simulated gastrointestinal digestion using consecutive pepsin–pancreatin for 240 min. The hydrolysates were fractionated using a dialysis tube, and its absorption was assessed using the everted Sprague–Dawley rat gut sac. Findings The tempe protein from the hydrolyzed pigeon pea exhibited higher ACE inhibitory (71.53%) activity than that from the boiled pigeon pea (53.04%) (p = 0.028). The bioactive peptide of the digested pigeon pea tempe consisted of low-molecular-weight peptides (&lt;1 kDa). The fraction also showed the highest ACE inhibition activity among the others (IC50 = 0.61 mg/mL, p = 0.021). Bioactive peptides from pigeon pea tempe were absorbed well in the small intestine, mainly in the jejunum. The activity of the absorbed peptides did not change considerably. Originality/value The activity of bioactive peptide of pigeon pea tempe was comparatively stable during digestion. It exhibited activity even after absorption in the small intestine. Thus, pigeon pea tempe can serve as an antihypertensive peptide source and alternative food for maintaining/reducing blood pressure.

The effects of Lycium barbarum water extract and fish collagen on milk proteolysis and in vitro angiotensin I-converting enzyme inhibitory activity of yogurt.

Plain and Lycium barbarum yogurt were made in the presence and absence of fish collagen. Yogurt samples were analyzed for acidification, milk protein proteolysis, angiotensin I-converting enzyme (ACE) inhibitory activity, and sensory evaluation during refrigerated storage for up to 21 days. The o-phthaldialdehyde peptides amount of L. barbarum yogurt both in the presence and absence of fish collagen were significantly increased during 14 days of storage. SDS-PAGE showed improvement in whey proteins degradation of L. barbarum yogurt with/without fish collagen after 3 weeks of storage. L. barbarum yogurt in absence of fish collagen was acting as a great ACE inhibitor reached up to 85% on day 7 of storage. The incorporation of L. barbarum and/or fish collagen affected to a small extent the overall sensory characteristics of yogurt. Yogurt supplemented with L. barbarum and/or fish collagen may lead to the improvement in the production and formulation of yogurt differing in their anti-ACE activity.

Angiotensin-Converting Enzyme Inhibitor Protects Against Cisplatin Nephrotoxicity by Modulating Kinin B1 Receptor Expression and Aminopeptidase P Activity in Mice.

Cisplatin is a highly effective chemotherapeutic agent. However, its use is limited by nephrotoxicity. Enalapril is an angiotensin I-converting enzyme inhibitor used for the treatment of hypertension, mainly through the reduction of angiotensin II formation, but also through the increase of kinins half-life. Kinin B1 receptor is associated with inflammation and migration of immune cells into the injured tissue. We have previously shown that the deletion or blockage of kinin B1 and B2 receptors can attenuate cisplatin nephrotoxicity. In this study, we tested enalapril treatment as a tool to prevent cisplatin nephrotoxicity. Male C57Bl/6 mice were divided into 3 groups: control group; cisplatin (20 mg/kg i.p) group; and enalapril (1.5 mg;kg i.p) + cisplatin group. The animals were treated with a single dose of cisplatin and euthanized after 96 h. Enalapril was able to attenuate cisplatin-induced increase in creatinine and urea, and to reduce tubular injury and upregulation of apoptosis-related genes, as well as inflammatory cytokines in circulation and kidney. The upregulation of B1 receptor was blocked in enalapril + cisplatin group. Carboxypeptidase M expression, which generates B1 receptor agonists, is blunted by cisplatin + enalapril treatment. The activity of aminopeptidase P, a secondary key enzyme able to degrade kinins, is restored by enalapril treatment. These findings were confirmed in mouse renal epithelial tubular cells, in which enalaprilat (5 μM) was capable of decreasing tubular injury and inflammatory markers. We treated mouse renal epithelial tubular cells with cisplatin (100 μM), cisplatin+enalaprilat and cisplatin+enalaprilat+apstatin (10 μM). The results showed that cisplatin alone decreases cell viability, cisplatin plus enalaprilat is able to restore cell viability, and cisplatin plus enalaprilat and apstatin decreases cell viability. In the present study, we demonstrated that enalapril prevents cisplatin nephrotoxicity mainly by preventing the upregulation of B1 receptor and carboxypeptidase M and the increased concentrations of kinin peptides through aminopeptidase activity restoration.

Anti-Hypertensive Activity of Novel Peptides Identified from Olive Flounder (Paralichthys olivaceus) Surimi.

There is a growing interest in the health benefits of functional foods. A benefit that has been long sought is the control of hypertension through dietary approaches. Hypertension has been implicated as a risk factor for cardiovascular disease and is therefore of clinical significance. Here, we aim to demonstrate the antihypertensive activity of novel peptides derived from surimi, a functional food ingredient made from refined fish myofibrillar proteins. Three peptides, Ile-Val-Asp-Arg (IVDR), Trp-Tyr-Lys (WYK), and Val-Ala-Ser-Val-Ile (VASVI), were isolated from surimi made from the olive flounder (Paralichthys olivaceus). Our results show that IVDR, WYK, and VASVI exhibited high Angiotensin I-converting Enzyme (ACE) inhibition activity. These peptides are also shown to increase phosphorylation of protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS), and significantly promote nitric oxide (NO) production in human umbilical vein endothelial cells. Oral administration of the peptides decreased blood pressure in spontaneously hypertensive rats (SHRs), thereby confirming that the peptides derived from surimi perform antihypertensive activity via the Akt/eNOS pathway. These results indicate that surimi made from P. olivaceus contains novel antihypertensive peptides that could be used to enhance the health benefits of food ingredients.

Improvement of chicken plasma protein hydrolysate angiotensin I-converting enzyme inhibitory activity by optimizing plastein reaction.

Chicken plasma protein hydrolysate (CPPH) was prepared by trypsin with angiotensin I‐converting enzyme (ACE) inhibitory activity of 53.5% ± 0.14% and the degree of hydrolysis (DH) of 16.22% ± 0.21% at 1 mg·ml−1; then, five proteases, including pepsin, trypsin, papain, alcalase, and neutrase, were employed to improve ACE inhibitory ability by catalyzing plastein reaction. The results indicated that trypsin‐catalyzed plastein reaction showed the highest ACE inhibitory activity. The exogenous amino acids of leucine, histidine, tyrosine, valine, and cysteine were selected to modify the CPPH. The leucine‐modified plastein reaction released the highest ACE inhibitory activity. The effects of four reaction parameters on plastein reaction were studied, and the optimal conditions with the purpose of obtaining the most powerful ACE inhibitory peptides from modified products were obtained by response surface methodology (RSM). The maximum ACE inhibition rate of the modified hydrolysate reached 82.07% ± 0.03% prepared at concentration of hydrolysates of 30%, reaction time of 4.9 hr, pH value of 8.0, temperature of 40°C, and E/S ratio of 5,681.62 U·g−1. The results indicated that trypsin‐catalyzed plastein reaction increased ACE inhibitory activity of chicken plasma protein hydrolysates by 28.57%.