Highest ACE-inhibitory Activity Research Articles

Isolation of novel ACE-inhibitory peptide from naked oat globulin hydrolysates in silico approach: Molecular docking, in vivo antihypertension and effects on renin and intracellular endothelin-1.

Naked oat globulin was hydrolyzed by alcalase, flavourzyme, pepsin, and trypsin in sequence. The hydrolysates (NOGH) were purified using gel chromatography, reversed-phase high performance liquid chromatography (RP-HPLC). Finally, fraction D7d with the highest ACE-inhibitory was subjected to liquid chromatography-mass spectrometry analysis and 14 peptides were identified. Of which, peptide SSYYPFK (890.4Da) was chose to synthesize based on in silico analysis. The SSYYPFK demonstrated high ACE-inhibitory activity (IC50 : 91.82µM) with competitive inhibition mode, and could effectively (P <0.05) lower the systolic blood pressure and diastolic pressure of spontaneously hypertensive rats at the concentration of 100 to 150mg/kg body weight. Molecular docking simulation demonstrated that SSYYPFK could bind with the active site S1 of ACE via short hydrogen bonds. It could remain the ACE-inhibitory activity after simulated gastrointestinal hydrolysis. Moreover, SSYYPFK showed acceptable renin and endothelin-1 suppressing capacity (47.59% and 27.88% at 1.5mg/mL, respectively). These results indicated that SSYYPFK may have similar antihypertensive mechanism with captopril, and could be develop to natural antihypertensive products. PRACTICAL APPLICATION: One novel ACE-inhibitory peptide SSYYPFK (890.4Da) was identified from naked oat globulin hydrolysates. It exhibited relatively high renin and intracellular endothelin-1 suppressing capacity, and could effectively (P <0.05) lower the systolic blood pressure and diastolic pressure of spontaneously hypertensive rats. This peptide could be used as natural and safe nutraceuticals and/or functional ingredients.

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.

Integrated approach for obtaining bioactive peptides from whey proteins hydrolysed using a new proteolytic lactic acid bacteria

In this study, we investigated the ability of Enterococcus faecalis 2/28, isolated from artisan cheese, to release biopeptides from whey proteins. We used an in silico approach for predicting the bioactivities of peptides generated by E. faecalis. The results of the in vitro study showed that the whey protein hydrolysates (WPHs) obtained had angiotensin-I-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) inhibitory activities, with inhibition of ACE being stronger than that of DPP-IV. To identify peptides that may be potential inhibitors of ACE, WPH with the highest ACE inhibitory activity was analysed using Sephadex G-75 gel filtration chromatography, Superdex peptide 10/300 GL size exclusion chromatography, and liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS). Among the identified peptides were ACE-inhibitory peptides (LDAQSAPLR, LKGYGGVSLPEW, and LKALPMH), antimicrobial peptides (AASDISLLDAQSAPLR, IIAEKTKIPAVF, IDALNENK, and VLVLDTDYK), DPP-IV-inhibitory peptides (LKALPMH, LKPTPEGDLEIL, LKGYGGVSLPE, LKPTPEGDLE, ILDKVGINY, and VLVLDTDYK), proliferation stimulating peptide (IDALNENK), and cytotoxic peptide (LIVTQTMK).

Isolation of Novel ACE-Inhibitory and Antioxidant Peptides from Quinoa Bran Albumin Assisted with an In Silico Approach: Characterization, In Vivo Antihypertension, and Molecular Docking

Albumin is the major fraction of quinoa protein that is characterized as having high nutritional value. However, until now, scant information is available on the bioactivity of quinoa albumin or its hydrolysates. To promote its usage, we extracted albumin in this study from quinoa bran assisted with cellulase and hemicellulose, and hydrolyzed it by alcalase and trypsin to produce bioactive peptides. The hydrolysates (QBAH) were purified by gel filtration and reversed-phase high-performance liquid chromatography (RP-HPLC), followed by identification using liquid chromatography–mass spectrometry (LC-MS/MS). Furthermore, based on in silico analysis, one angiotensin-I converting enzyme (ACE)-inhibitory and antioxidant peptide, RGQVIYVL (946.6 Da), and two antioxidant peptides, ASPKPSSA (743.8 Da), and QFLLAGR (803.5 Da), from QBAH were synthesized. RGQVIYVL showed a high ACE-inhibitory activity (IC50 = 38.16 μM) with competitive mode of inhibition, and showed significant antihypertensive effect in spontaneously hypertensive rats at a concentration of 100–150 mg/kg body weight (bw). Molecular docking simulation showed that it could interact with the active ACE site via hydrogen bonds with high binding power. Moreover, RGQVIYVL, ASPKPSSA, and QFLLAGR all demonstrated high ·OH scavenging activity (IC50 = 61.69–117.46 μM), ABTS+ scavenging activity (58.29–74.28%) and Fe2+ chelating ability (32.54–82.48% at 0.5 mg/mL). They could also retain activity after gastrointestinal enzyme digestion. These results indicate that quinoa albumin is a potential source of bioactive peptides possessing antioxidant and ACE-inhibitory activities.

The necessity of walnut proteolysis based on evaluation after in vitro simulated digestion: ACE inhibition and DPPH radical-scavenging activities

This study aimed to evaluate the necessity of enzymatic hydrolysis for walnut peptide preparation based on a novel evaluation approach. Defatted walnut meal hydrolysate (DWMH) was prepared by hydrolyzing defatted walnut meal (DWM) with alcalase, and gastrointestinal digestion of DWM and DWMH was simulated in vitro using pepsin and pancreatin. The peptide and free amino acid (FAA) contents, angiotensin-I-converting enzyme (ACE) inhibitory activity, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity and molecular weight distributions of DWM, DWMH and their gastric and gastrointestinal digestive fluids were compared. Results showed that DWM could be well digested. High peptide content (21.66 mg/mL) with MW < 3000 Da and more FAAs (8.09 mg/mL) were observed in DWM digests. In addition, DWM digests had high ACE inhibitory activity (42.9%) and DPPH radical-scavenging activity (62.58%), which showed no significant difference when compared with DWMH digests. The above results indicate that enzymatic hydrolysis seems unnecessary for the production of walnut peptides; at the least, hydrolysis with alcalase was unnecessary for producing peptides with significant ACE inhibitory and DPPH radical-scavenging activities.

Angiotensin converting enzyme inhibitory peptide fractions from Tibet wild peach kernel protein hydrolysates

In this study, the peach kernel proteins were extracted and treated with alkaline proteinase to generate peach kernel protein hydrolysate (PKH), which showed angiotensin converting enzyme (ACE) inhibition activity. The hydrolysate was separated into four fractions and their anti-ACE activities were investigated. Our results showed that all PKHs had anti-ACE activity, and the lowest molecular weight fraction PKH4 had the highest ACE inhibitory activity. Lineweaver–Burk plots illustrated that the inhibition types of PKH3 and PKH4 were non-competitive. The Ki of PKH4 was lower than Ki of PKH3; suggesting PKH4 had high affinity to ACE. Amino acid composition analysis showed that the best anti-ACE peptide PKH4 possessed high levels of hydrophobic amino acids, branched-chain amino acids, and aromatic amino acids. In summary, our findings demonstrated that high anti-ACE activity is negatively related to the size of the PKHs and possibly the composition of amino acids, and the PKH4 was the best ACE inhibitor. Further, peach kernel peptides can be developed as a functional food for patients with hypertension.

Jack bean as tempe ingredients: The safety study and fate of protein against gastrointestinal enzymes

This study evaluated the change of hydrogen cyanide (HCN) content and concanavalin A (Con A) activity during the processing of jack bean tempe. In addition, the fate of protein of cooked tempe following in vitro gastrointestinal digestion was also investigated. The jack bean tempe was prepared by the step of the soaking-boiling-soaking-boiling-fermentation process. The mature tempe was harvested on 48 h of fermentation and followed by the cooking process for 10 min (T10) and 20 min (T20). The results showed the soaking, soaking-boiling, soaking-boiling-soaking, and soaking-boiling-soaking-boiling were able to decrease the HCN content of jack bean as much as 3.98; 85.88; 92.88 and 97.95%, respectively. It did not significantly change during fermentation with content for mature tempe was as low as 0.71 ppm, which is categorized as a safe level according to FAO. The haemagglutination assay of Con A showed the protein extracted from raw jack bean provided red blood cell clotting, while it was not found in the protein extracted from boiled jack bean and jack bean tempe. In the in vitro digestion model, both T10 and T20 samples showed that there was no significant change in peptides content before and after hydrolysis using pepsin (p<0.05). The action of gastrointestinal enzymes improved the released of the bioactive peptides which have the ability to inhibit angiotensin – I – converting enzyme (ACE). It can be concluded that the jack bean was the safe protein source for consumption as tempe. Furthermore, the protein of cooked tempe was highly hydrolyzed following in vitro gastrointestinal digestion produced bioactive peptides with high ACE inhibitory activity.

Comparative peptidomic profile and bioactivities of cooked beef, pork, chicken and turkey meat after in vitro gastro-intestinal digestion

This study was designed to investigate the potential contribution of bioactive peptides to the biological activities related to the consumption of pork, beef, chicken and turkey meat following in vitro gastro-intestinal digestion. After extraction of the peptidic fractions from digested samples, the bioactivities were evaluated by in vitro antioxidant activity as well as angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) inhibition assays. Pork and turkey meat appeared to be the best sources of antioxidant peptides. Pork was found to be the best source of DPP-IV-inhibitory peptides whereas chicken meat supplied peptides with the highest ACE-inhibitory activity. The comprehensive analysis of the peptidomic profile of digested samples was performed by nano-LC-ESI-QTOF MS/MS analysis. A total of 217, 214, 257 and 248 peptides were identified in digested pork, beef, chicken and turkey meat, respectively. Chicken and turkey meat showed the highest similarity in peptide sequences with 202 common peptides. Sixty-two peptides matched with sequences with previously demonstrated biological activity. In particular, 35 peptides showed ACE-inhibitory activity and 23 DPP-IV inhibitory activity. Twenty-two bioactive peptides were commonly released from the different types of meat. The relative amount of identified bioactive peptides were positively correlated to the biological activities of the different digested meats. Biological significanceThe present study describes for the first time a comprehensive peptide profile of four types of meat after in vitro gastro-intestinal digestion. The peptide inventory was used to identify 62 bioactive peptides with ACE- and DPPIV-inhibitory and antioxidant activities. The bioactivity analysis revealed interesting and significant differences between the studied meats. The originality of this work lay in the description of intrinsic differences in physiological functions after the ingestion of meat proteins from different species. In a context in which the current research scene relates meat consumption to the onset of chronic pathologies, this peptide profiling and bioactivity analysis shed light on the possible health benefits of peptides released from meat proteins. In fact, this paper represents a sort of detailed peptide list that may help to predict which peptides could be generated after meat intake and detectable at gastro-intestinal level. It also provides a thorough investigation of novel biological activities associated to meat protein hydrolysates, giving a new positive aspect to meat consumption.

Angiotensin Converting Enzyme (ACE) Inhibitory Activity of Peptide Fraction of Germinated Pigeon Pea (&lt;i&gt;Cajanus cajan&lt;/i&gt; (L.) Millsp.)

During the germination process, seeds can release various types of peptides due to the degradation of storage proteins. Some of these peptides can have biological activity (bioactive peptides). The objective of this study was to determine the ACE inhibitory activity of germinated pigeon pea peptide extract at various germination times and to carry out the fractionation to the extract to get the most active peptide fraction. The results showed that the highest activity of peptide extract was found on the 4th-day germination of pigeon pea with an IC50 value of 63.46 μg/mL. The peptide extract was further fractionated by centrifugal ultrafiltration method and it was found that the peptide fraction &lt; 3 kDa had the highest ACE inhibitory activity with an IC50 value of 57.79 μg/mL. The result of identification with the LCMS method to the fraction was able to detect 4 types of the peptide with a molecular weight of 230.304, 294.303, 441.436, and 570.591 Da. These results suggested that the peptide fraction of germinated pigeon pea has the potency as an ACE inhibitory nutraceutical.

Yoghurt-Type Gels from Skim Sheep Milk Base Enriched with Whey Protein Concentrate Hydrolysates and Processed by Heating or High Hydrostatic Pressure.

An objective of the present study was the enrichment of skim sheep yoghurt milk base with hydrolysates (WPHs) of whey protein concentrate (WP80) derived from Feta cheesemaking. Moreover, the use of high hydrostatic pressure (HP) treatment at 600 MPa/55 °C/10 min as an alternative for heat treatment of milk bases, was studied. In brief, lyophilized trypsin and protamex hydrolysates of WP80 produced under laboratory conditions were added in skim sheep milk. The composition and heat treatment conditions were set after the assessment of the heat stability of various mixtures; trisodium citrate was used as a chelating agent, when needed. According to the results, the conditions of heat treatment were more important for the physical properties of the gel than the type of enrichment. High pressure treatment resulted in inferior gel properties, irrespective of the type of enrichment. Supplementation of skim sheep milk with whey protein hydrolysates at >0.5% had a detrimental effect on gel properties. Finally, skim sheep milk base inoculated with fresh traditional yoghurt, resulted in yoghurt-type gels with high counts of Lb. delbrueckii subsp. bulgaricus and Str. thermophilus -close to the ideal 1:1- and with a high ACE inhibitory activity >65% that were not essentially affected by the experimental factors.

Purification, Characterization and Evaluation of Inhibitory Mechanism of ACE Inhibitory Peptides from Pearl Oyster (Pinctada fucata martensii) Meat Protein Hydrolysate.

Angiotensin-I-converting enzyme (ACE) inhibitory peptides derived from natural products have shown a blood pressure lowering effect with no side effects. In this study, two novel ACE inhibitory peptides (His-Leu-His-Thr, HLHT and Gly-Trp-Ala, GWA) were purified from pearl oyster (Pinctada fucata martensii) meat protein hydrolysate with alkaline protease by ultrafiltration, polyethylene glycol methyl ether modified immobilized metal ion affinity medium, and reverse-phase high performance liquid chromatography. Both peptides exhibited high ACE inhibitory activity with IC50 values of 458.06 ± 3.24 μM and 109.25 ± 1.45 μM, respectively. Based on the results of a Lineweaver-Burk plot, HLHT and GWA were found to be non-competitive inhibitor and competitive inhibitor respectively, which were confirmed by molecular docking. Furthermore, the pearl oyster meat protein hydrolysate exhibited an effective antihypertensive effect on SD rats. These results conclude that pearl oyster meat protein is a potential resource of ACE inhibitory peptides and the purified peptides, HLHT and GWA, can be exploited as functional food ingredients against hypertension.

Identification of bioactive peptides from brewers’ spent grain and contribution of Leu/Ile to bioactive potency

Abstract Brewer's spent grain (BSG) is a co-product of the brewing industry and is a potentially rich source of bioactive peptides. A BSG protein hydrolysate, manufactured at a semi-pilot scale, mediated significant hypotensive effects 6 h after ingestion in spontaneously hypertensive rats. This hydrolysate was fractionated and further analysed by UPLC-ESI-MS/MS for peptide identification. The peptides, IPY and LPY demonstrated the highest antioxidant activity (0.37 ± 0.02 and 0.34 ± 0.02 µmol Trolox equivalents µM peptide−1, respectively), IPLQP and LPLQP had the highest ACE inhibitory activity (IC50: 3.10 ± 0.60 and 3.17 ± 0.60 µM, respectively) while IPVP had the highest DPP-IV inhibitory activity (IC50: 38.67 ± 5.94 µM). Overall, peptides containing I had higher in vitro bioactivities when compared to peptides having L. Novel BSG peptides were identified with potential for application as naturally derived ingredients for the management of cardiovascular disease and type 2 diabetes.

Purification and Characterization of Angiotensin I Converting Enzyme Inhibitory Peptide from Sand eel Protein Hydrolysates

Among the mechanisms associated with hypertension, angiotensin I converting enzyme (ACE) plays an important role in the regulation of blood pressure. The purpose of this study is purification and characterization of an ACE inhibitory peptide derived from enzymatic hydrolysates of sand eel (Hypoptychus dybowskii) protein. Among six hydrolysates, the trypsin hydrolysate had the highest ACE inhibitory activity. A peptide with the strongest ACE inhibitory activity was isolated from the trypsin hydrolysate using consecutive chromatography. The IC50 value of the purified ACE inhibitory peptide was 89.3 μM. Amino acid sequence of the purified peptide was identified to be Pro-Asp-His-Gly-Leu-Tyr-Val, with molecular weight of 907 Da and the Lineweaver-Burk plots suggest that it acts as a competitive inhibitor against ACE. Taken together, these results suggest that sand eel protein hydrolysate are a satisfactory source to inhibit ACE with the potential applications in physiologically functional foods with antihypertensive activity.

In Vitro and in Vivo Studies on the Angiotensin-Converting Enzyme Inhibitory Activity Peptides Isolated from Broccoli Protein Hydrolysate.

In the present study we purified and identified peptides from broccoli protein hydrolysates and evaluated their angiotensin-converting enzyme (ACE) inhibitory activity in vitro and hypotensive effect in vivo. Three ACE inhibitory peptides were isolated and identified as IPPAYTK, LVLPGELAK, and TFQGPPHGIQVER, and their inhibitory IC50 values were 23.5, 184.0, and 3.4 μM, respectively. We then investigated the effect of gastrointestinal digestion on ACE inhibitory activity. We detected almost two times the ACE inhibitory activity of the peptide LVLPGELAK following simulated digestion than prior to digestion. LVLPGE and LAK, two novel peptides exhibiting high ACE inhibitory activity, were discovered following digestion and possessed IC50 values of 13.5 and 48.0 μM, respectively. The hypotensive effect of the peptides was assessed after oral administration to spontaneous hypertensive rats (SHRs). We found that LVLPGE and LAK demonstrated a significant hypotensive effect in vivo. Protein from broccoli may thus constitute a potential antihypertensive peptide source.

Formation of ACE-inhibitory peptides during fermentation of jack bean tempe inoculated by usar Hibiscus tiliaceus leaves starter

Jack bean is one of the potential legumes as a source of ACE-inhibitory peptides in tempe fermentation due to its high protein content and amino acids composition. A traditional inoculum for tempe fermentation is usar from Hibiscus tiliaceus leaves. The aim of this study was to investigate the optimum tempe fermentation time inoculated using usar on the formation of ACE-inhibitory peptides. The study applied the prolonged tempe fermentation (120 h) at room temperature (+30°C). The change of pH, soluble protein, protease activity, and ACE-inhibitory activity during tempe fermentation were determined using standard methods. There were significant differences (α=0.05) in pH, proteolytic activity, soluble protein content, and ACE-inhibitory activity during tempe fermentation. The highest protease activity was produced at 96 h of fermentation while the highest soluble protein content was produced at 120 h of fermentation with the value of 12.71 unit/g and 3.65 mg/mL, respectively. The highest ACE-inhibitory activity was reached at 72 h of fermentation (53.89 %). Conclusion: The optimum fermentation time of the formation of ACE-inhibitory peptide was at 72 h of fermentation.

In vitro Angiotesin-1-converting enzyme, α-amylase and α-glucosidase inhibitory and antioxidant activities of Luffa cylindrical (L.) M. Roem seed protein hydrolysate

In recent times, researchers have explored food derived peptides to circumvent the side effects of synthetic drugs. This study therefore examined the amino acid constituents, in vitro antioxidant activities, angiotensin-1-converting enzyme (ACE), α-glucosidase and α-amylase inhibition kinetics of protein hydrolysate obtained from the seed of Luffa cylindrica. The peptide yield by pepsin (16.93 ± 0.28%) and trypsin (13.20 ± 1.02%) were significantly lower than that of Alcalase (34.04 ± 1.96%). Alcalase hydrolysate however displayed the highest ferric reducing antioxidant capacity (FRAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and H2O2 scavenging activities (0.63%, 85.88% and 41.69% respectively), while the highest superoxide scavenging activity was shown by peptic hydrolysate (57.89%). The ACE inhibition by the hydrolysates with IC50 of 0.32–0.93 mg/mL, increased as the concentration of the peptic hydrolysate increased with the highest ACE-inhibitory activity (74.99 ± 0.43%) at 1.2 mg/mL of peptic hydrolysate. Tryptic and Alcalase hydrloysates exhibited a strong α-amylase inhibition having 27.96 ± 0.06% and 36.36 ± 0.71% inhibitory capacity respectively with IC50 of 1.02–3.31 mg/mL. Alcalase hydrolysates demonstrated the strongest inhibition (65.81 ± 1.95%), followed by tryptic hydrolysates (54.53 ± 0.52%) in a concentration-dependent inhibition of α-glucosidase (IC50, 0.48–0.80 mg/mL). Kinetic analysis showed that ACE-inhibition by different concentrations of Alcalase, pepsin and trypsin hydrolysates is uncompetitive, mixed-type and non-competitive respectively. α-Amylase was non-competitively inhibited while α-glucosidase was un-competitively inhibited by all the hydrolysates. The total amino acid concentration for Alcalase, trypsin and pepsin hydrolysates was 53.51g/100g, 75.40g/100g and 85.42g/100g of Luffa cylindrica seed protein hydrolysate respectively, with glutamate being the most concentrated essential amino acid in all the three hydrolysates. From these results, it can be deduced that Luffa cylindrica seed Alcalase and tryptic protein hydrolysates may play critical and indispensible role as bio-tools in diabetes and hypertension treatment.

Kinetics of angiotensin -1 converting enzyme inhibition and antioxidative properties of Azadirachta indica seed protein hydrolysates

Neem (Azadirachta indica) seed protein hydrolysates were investigated for in vitro antioxidant and angiotensin 1-converting enzyme (ACE)-inhibitory activities. Neem seed proteins were hydrolysed using pepsin, trypsin and Alcalase. The degree of pepsin hydrolysis of neem seed protein was significantly higher (p < 0.05) than those of trypsin and Alcalase hydrolysis. Proteolytic hydrolysis of the isolate resulted in hydrolysates with improved Arg/Lys ratio, with pepsin hydrolysates still being able to maintain an acceptable level of essential amino acids comparable to that of the isolate. At 2.5 mg/mL, pepsin neem seed protein hydrolysate (NSPH) demonstrated the strongest antioxidant activity with 67.15 % and 50.07 % DPPH- and superoxide anion radical-scavenging activities, respectively, while trypsin NSPH had the highest ferric-reducing power. Using N-[3-(2-furyl)acryloyl]-L-phenylalanyl-glycyl-glycine (FAPGG) as substrate, NSPHs strongly inhibited ACE (69.20–80.39 %) in a concentration-dependent manner. Pepsin NSPH had higher ACE-inhibitory activity than trypsin and Alcalase NSPHs. Kinetic studies showed the mechanism of ACE inhibition to be mixed-type with Ki values of 0.62, 0.84, 1.5 for pepsin, trypsin and alcalase NSPH, respectively. These results suggest that NSPH can be used as a potential nutraceutical with antioxidant capacity and inhibitory activity against ACE.

Angiotensin-converting enzyme inhibitory peptides from Lactobacillus delbrueckii QS306 fermented milk

Angiotensin-converting enzyme inhibitory peptides were isolated and identified from milk fermented using Lactobacillus delbrueckii QS306. The peptide with the highest angiotensin-converting enzyme inhibitory activity (C5) was purified using ultrafiltration with 10 and 3 kDa molecular mass cut-off membranes, Sephadex G-15 (Sigma-Aldrich, St. Louis, MO) gel filtration chromatography, reversed-phase HPLC, and Orbitrap Elite (Thermo Fisher Scientific Inc., Waltham, MA) liquid chromatography-tandem mass spectrometry. We obtained peptide LPYPY by microbial fermentation, which was derived from κ-casein f (AA 77-81). We synthesized LPYPY using an Fmoc solid-phase synthesis method and explored the secondary structure of the pentapeptide. The half maximal inhibitory concentration for the angiotensin-converting enzyme inhibitory activity of LPYPY was 12.87 μg/mL. The results provide additional information for ongoing research and the development of functional foods having antihypertensive effects.

A novel angiotensin-I converting enzyme inhibitory peptide derived from the glutelin of vinegar soaked black soybean and its antihypertensive effect in spontaneously hypertensive rats.

Vinegar soaked black soybean is a traditional Chinese food widely used for the treatment of hypertension. While its pharmacodynamic substance was not fully unveiled. It contained abundant glutelin, thus the purpose of this study was to obtain potent antihypertensive peptides from vinegar soaked black soybean. Black soybean was soaked with vinegar and then glutelin was first catalyzed by alcalase. Ultrafiltration, ion exchange chromatography and reversed-phase high performance liquid chromatography were sequentially applied to separate and purify the angiotensin-I converting enzyme (ACE) inhibitory peptides from glutelin hydrolysates. As a result, the fraction L1-4 with the highest ACE inhibitory activity (83.41%) at the final concentration of 0.01 mg/ml was obtained and five peptides were then identified. These peptides were further optimized by virtual screening combining with in silico proteolysis. Finally, a novel tetrapeptide Phe-Gly-Ser-Phe (FGSF) was obtained. FGSF exhibited high in vitro ACE inhibitory activity (IC50 = 117.11 μM) and in vivo hypotensive effect which maximally reduced systolic blood pressure of 21.95 mmHg at 20 mg/kg body weight in spontaneously hypertensive rats. Our study demonstrated that FGSF derived from vinegar soaked black soybean might be used as a promising ingredient for pharmaceuticals against hypertension and its related diseases.

Nutritional composition and angiotensin converting enzyme inhibitory activity of blue lupin (Lupinus angustifolius)

The nutritional, protein and amino acid compositions of blue lupin (Lupinus angustifolius) flour were studied. The angiotensin converting enzyme (ACE) inhibitory activity of lupin protein isolate (LPI) hydrolysates prepared using Alcalase and Flavourzyme, and the Osborne protein fractions hydrolysates prepared using Alcalase were determined. Lupin flour was high in protein (43 g/100 g) and dietary fiber (34 g/100 g) but low in carbohydrate (4.8 g/100 g) and ash (3.4 g/100 g). Results from a sequential Osborne extraction procedure showed that lupin protein was comprised of 56% globulin, 26% albumin and 19% glutelin, while prolamin was only found in trace amounts. Lupin protein was high in Lys but limiting in Met. SDS-PAGE analysis suggested that protein hydrolysis catalyzed using Alcalase was more effective than Flavourzyme as shown by the presence of lower molecular weight peptides in the former. LPI hydrolysates prepared using Alcalase showed high ACE inhibitory activities with IC50 values ranging from 0.10 to 0.21 mg/ml. The results suggested that the globulin fraction was the main contributor towards the ACE inhibitory activity observed in lupin protein.