Highest ACE-inhibitory Activity Research Articles

Investigation of the Interaction Between Angiotensin-Converting Enzyme (ACE) and ACE-Inhibitory Tripeptide from Casein

Angiotensin-converting enzyme (ACE) inhibitory peptides exhibit antihypertensive effects by inhibiting ACE activity, and the study of the interaction between ACEs and inhibitory peptides is important for exploring new therapeutic strategies. In this study, the ACE-inhibitory peptide isolated from casein hydrolysate with the amino acid sequence Leu–Leu–Tyr (LLY) exhibited high ACE-inhibitory activity and stability, which holds significant implications for biochemistry and pharmaceutical applications. Furthermore, systematic investigations were conducted on the interaction between ACE and LLY through various approaches. The Lineweaver–Burk plot indicated the non-competitive inhibition pattern of LLY, suggesting that it binds to the enzyme at the non-active site, and the results were further validated by a molecular docking study. Additionally, multispectral experiments and atomic force microscopy were conducted to further elucidate the underlying mechanism of peptide activity. The findings indicated that LLY could induce a conformational change in ACE, thereby inhibiting its activity. This study contributes to a deeper understanding of the mechanism of action of ACE-inhibitory peptides and bears important significance for drug development in hypertension.

Prediction and Validation of Proline-containing Tripeptides with Angiotensin I-converting Enzyme Inhibitory Activity Using Machine Learning Models

Background: Numerous inhibitory peptides against angiotensin I-converting enzyme, a target for hypertension treatment, have been found in previous studies. Recently, machine learning screening has been employed to predict unidentified inhibitory peptides using a database of known inhibitory peptides and descriptor data from docking simulations. Objective: The aim of this study is to focus on angiotensin I-converting enzyme inhibitory tripeptides containing proline, to predict novel inhibitory peptides using the machine learning algorithm PyCaret based on their IC50 and descriptors from docking simulations, and to validate the screening method by machine learning by comparing the results with in vitro inhibitory activity studies. Methods: IC50 of known inhibitory peptides were collected from an online database, and descriptor data were summarized by docking simulations. Candidate inhibitory peptides were predicted from these data using the PyCaret. Candidate tripeptides were synthesized by solid-phase synthesis and their inhibitory activity was measured in vitro. Results: Seven novel tripeptides were found from the peptides predicted to have high inhibitory activity by machine learning, and these peptides were synthesized and evaluated for inhibitory activity in vitro. As a result, the proline-containing tripeptide MPA showed high inhibitory activity, with an IC50 value of 8.6 µM. Conclusion: In this study, we identified a proline-containing tripeptide with high ACE inhibitory activity among the candidates predicted by machine learning. This finding indicates that the method of predicting by machine learning is promising for future inhibitory peptide screening efforts.

Chemical characterization and angiotensin-I converting enzyme inhibitory activity of Indonesian stinky beans

The chemical composition of four Indonesian stinky beans has been explored. Those bean are Petai (Parkia speciosa), Lamtoro Gung (Leucaena leucochepala ssp. Glabrata (Rose) S. Zarate), Jengkol (Pithecellobium jiringa) and Kabau (Archidendron bubalinum). This exploration belongs to the local food utilization research theme of functional food sources. Those beans have a unique flavour and usually lead to foul stools, sweat, urine or mouth odour. Their intense flavour may be due to the content of amino acids. High hydrophobic and negative charge hydrophilic amino acids are crucial in preventing hypertension through inhibition of angiotensin I-converting enzyme (ACE) activity. This study evaluated the chemical properties of beans and its angiotensin I-converting enzyme inhibitory (ACE-I) peptides. The amino acid profile was determined as preliminary data to ensure the content of hydrophobic and negative charge hydrophilic amino acids. Their ability to inhibit ACE was studied to represent an antihypertensive effect. In vitro gastrointestinal digestion was applied to obtain more small molecular peptides and evaluate their ACE-I activity after digestion. Petai has the highest glutamic acid (20.90 g/100 g protein d.b.), lysine (13.31 g/100 g protein d.b.), arginine (11.76 g/100 g protein d.b.), leucine (10.98 g/100 g protein d.b.), and aspartic acid (10.72 g/100 g protein d.b.). Fresh Jengkol has the highest ACE-I activity (67.59%). Subsequential digestion by pepsin and pancreatin improves the ACE-I activity, and Kabau had the highest (79.87%). Based on the results, Indonesian stinky beans can prevent hypertension by inhibiting ACE activity and being used as a protein source alternative

Angiotensin-Converting Enzyme and Renin-Inhibitory Activities of Protein Hydrolysates Produced by Alcalase Hydrolysis of Peanut Protein.

Hypertension is a major controllable risk factor associated with cardiovascular disease (CVD) and overall mortality worldwide. Most people with hypertension must take medications that are effective in blood pressure management but cause many side effects. Thus, it is important to explore safer antihypertensive alternatives to regulate blood pressure. In this study, peanut protein concentrate (PPC) was hydrolyzed with 3-5% Alcalase for 3-10 h. The in vitro angiotensin-converting enzyme (ACE) and renin-inhibitory activities of the resulting peanut protein hydrolysate (PPH) samples and their fractions of different molecular weight ranges were determined as two measures of their antihypertensive potentials. The results show that the crude PPH produced at 4% Alcalase for 6 h of hydrolysis had the highest ACE-inhibitory activity with IC50 being 5.45 mg/mL. The PPH samples produced with 3-5% Alcalase hydrolysis for 6-8 h also displayed substantial renin-inhibitory activities, which is a great advantage over the animal protein-derived bioactive peptides or hydrolysate. Remarkably higher ACE- and renin-inhibitory activities were observed in fractions smaller than 5 kDa with IC50 being 0.85 and 1.78 mg/mL. Hence, the PPH and its small molecular fraction produced under proper Alcalase hydrolysis conditions have great potential to serve as a cost-effective anti-hypertensive ingredient for blood pressure management.

Antioxidant capacity and peptidomic analysis of in vitro digested Camelina sativa L. Crantz and Cynara cardunculus co-products

In recent decades, the food system has been faced with the significant problem of increasing food waste. Therefore, the feed industry, supported by scientific research, is attempting to valorise the use of discarded biomass as co-products for the livestock sector, in line with EU objectives. In parallel, the search for functional products that can ensure animal health and performances is a common fundamental goal for both animal husbandry and feeding. In this context, camelina cake (CAMC), cardoon cake (CC) and cardoon meal (CM), due valuable nutritional profile, represent prospective alternatives. Therefore, the aim of this work was to investigate the antioxidant activity of CAMC, CC and CM following in vitro digestion using 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), Ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) assays. Total phenolic content (TPC) and angiotensin converting enzyme (ACE) inhibitory activity, actively involved in modulating antioxidant properties, were also studied. Further, a peptidomic analysis was adopted to substantiate the presence of bioactive peptides after in vitro digestion. The results obtained confirmed an interesting nutritional profile of CAMC, CC and CM and relevant antioxidant and ACE inhibitory activities. In particular, considering antioxidant profile, CM and CC revealed a significantly higher (10969.80 ± 18.93 mg TE/100 g and 10451.40 ± 149.17 mg TE/100 g, respectively; p < 0.05) ABTS value than CAMC (9511.18 ± 315.29 mg TE/100 g); a trend also confirmed with the FRAP assay (306.74 ± 5.68 mg FeSO4/100 g; 272.84 ± 11.02 mg FeSO4/100 g; 103.84 ± 3.27 mg FeSO4/100 g, for CC, CM and CAMC, respectively). Similar results were obtained for TPC, demonstrating the involvement of phenols in modulating antioxidant activity. Finally, CAMC was found to have a higher ACE inhibitory activity (40.34 ± 10.11%) than the other matrices. Furthermore, potentially bioactive peptides associated with ACE inhibitory, anti-hypertensive, anti-cancer, antimicrobial, antiviral, antithrombotic, DPP-IV inhibitory and PEP-inhibitory activities were identified in CAMC. This profile was broader than that of CC and CM. The presence of such peptides corroborates the antioxidant and ACE profile of the sample. Although the data obtained report the important antioxidant profile of CAMC, CC, and CM and support their possible use, future investigations, particularly in vivo trials will be critical to evaluate and further investigate their effects on the health and performance of farm animals.

Angiotensin-I-converting enzyme and renin inhibitions by antioxidant shrimp shell protein hydrolysate and ultrafiltration peptide fractions

Protein hydrolysates with 20% and 30% degrees of hydrolysis (DH) were produced from alcalase hydrolysis of Pacific white shrimp shells. The study aimed to investigate the antioxidant and antihypertensive activities of these protein hydrolysates, focusing on peptide fractions of various molecular weights (MW) obtained through ultrafiltration. The 30% DH protein hydrolysate (SSPH) showed the highest antioxidant activities and was subjected to ultrafiltration to produce peptides of various molecular weights (MW) (F1:10–50, F2:5–10, F3:3–5, F4:1-3, and F5:<1 kDa). SSPH showed higher hydrophilic and non-essential amino acid content, among which alanine and aspartic acid were at higher levels. The obtained peptide fractions were analyzed for various antioxidant activities and inhibitory activities against angiotensin-converting enzyme and renin. F4 and F2 samples showed the highest DPPH (2.00 mM TE/g sample) and ABTS (60.68 mM TE/g sample) radical scavenging activities, respectively. Superoxide and hydrogen peroxide radical scavenging activity augmented with decreasing MW, aside from for F1, which showed higher activity than F2–F4 (p < 0.05). The highest ACE-inhibitory activity was found for the F2 fraction (44%–55%), and renin inhibitory activity increased with decreasing MW, in which F5 (12%–22%) was the most effective (p < 0.05). F5 showed 6 major peptides, among which KLVRGSKS and LPKKCLSARPG were the dominant sequences. Thus, this study suggests that shrimp shell protein isolate could be an alternative protein source for peptides with various antioxidant and antihypertensive activities, with potential applications in functional foods and nutraceuticals aimed at mitigating oxidative stress and hypertension.

Study on the Digestion-Induced Changes in the Characteristics and Bioactivity of Korean Native and Overseas Cattle-Derived Peptides.

This study was conducted to compare and analyze the changes in the biochemical characteristics and biological activity of peptide extracts derived from Chickso, Hanwoo, and Wagyu beef during digestion. The results of the in vitro digestion analysis revealed that the digestion rate, total free amino acid content, and antioxidant and antihypertensive activities of Chickso loin and shank myofibrillar proteins were significantly higher (p<0.05) than those of Hanwoo and Wagyu loin and shank myofibrillar proteins. Particularly, the peptide extracts of Chickso loin and shank had a high angiotensin-converting enzyme inhibitory activity. In mice in vivo digestion experiment, the blood serum of mice fed with Chickso loin peptide extract (<10 kDa) showed the highest antioxidant enzyme activity. Thus, Chickso peptide extracts were deemed to be similar or more bioactive than Hanwoo and Wagyu peptide extracts, and can be used as bioactive materials.

A novel angiotensin I-converting enzyme inhibitory peptide from walnut (Juglans sigillata) protein hydrolysates and its evaluation in Ang II-induced HUVECs and hypertensive rats

This study aims to seek angiotensin-I-converting enzyme inhibitory (ACEi) peptides from walnut using different enzymatic hydrolysis, and further to validate the potent ACEi peptides identified and screened via peptidomics and in silico analysis against hypertension in spontaneously hypertensive rats (SHRs). Results showed that walnut protein hydrolysate (WPH) prepared by combination of alcalase and simulated gastrointestinal digestion exhibited high ACEi activity. WPH was separated via Sephadex-G25, and four peptides were identified, screened and verified based on their PeptideRanker score, structural characteristic and ACE inhibition. Interestingly, FDWLR showed the highest ACEi activity with IC50 value of 8.02 μg/mL, which might be related to its close affinity with ACE observed in molecular docking. Subsequently, high absorption and non-toxicity of FDWLR was predicted via in silico absorption, distribution, metabolism, excretion and toxicity. Furthermore, FDWLR exhibited positively vasoregulation in Ang II-induced human umbilical vein endothelial cells, and great blood pressure lowering effect in SHRs.

Characterization of a novel aspartic protease from Trichoderma asperellum for the preparation of duck blood peptides

A novel aspartic protease gene (TaproA1) from Trichoderma asperellum was successfully expressed in Komagataella phaffii (Pichia pastoris). TaproA1 showed 52.8% amino acid sequence identity with the aspartic protease PEP3 from Coccidioides posadasii C735. TaproA1 was efficiently produced in a 5 L fermenter with a protease activity of 4092 U/mL. It exhibited optimal reaction conditions at pH 3.0 and 50 °C and was stable within pH 3.0–6.0 and at temperatures up to 45 °C. The protease exhibited broad substrate specificity with high hydrolysis activity towards myoglobin and hemoglobin. Furthermore, duck blood proteins (hemoglobin and plasma protein) were hydrolyzed by TaproA1 to prepare bioactive peptides with high ACE inhibitory activity. The IC50 values of hemoglobin and plasma protein hydrolysates from duck blood proteins were 0.105 mg/mL and 0.091 mg/mL, respectively. Thus, the high yield and excellent biochemical characterization of TaproA1 presented here make it a potential candidate for the preparation of duck blood peptides.Key points• An aspartic protease (TaproA1) from Trichoderma asperellum was expressed in Komagataella phaffii.• TaproA1 exhibited broad substrate specificity and the highest activity towards myoglobin and hemoglobin.• TaproA1 has great potential for the preparation of bioactive peptides from duck blood proteins.

Extraction of citrus pectin using pressurized carbon dioxide and production of its oligosaccharides

In this study, we utilized pressurized carbon dioxide (pCO2) for pectin extraction from citrus residues because of its potential to produce acid without chemicals, that is non-toxic, green technology for humans and the environment. The pCO2 was performed at 2.5 MPa and 90 °C for 90 min, while the conventional method (CM) for pectin extraction using HCl was performed under atmospheric pressure at 90 °C for 90 min. Pectin extraction yields with pCO2 depended on the type of citrus fruit and were lower than those obtained with the CM. However, pCO2-extracted pectin (pCO2-pectin) provided a higher degree of esterification (DE), neutral sugar side-chain substitution on the pectate backbone, and greater molecular size than those of pectin extracted using the conventional method (CM-pectin). Pectin oligosaccharide (POS) was prepared from CM-pectin and pCO2-pectin using viscozyme L hydrolysis under optimum conditions. These POSs were then designated as CM-POS and pCO2-POS, respectively. Both pCO2-POS and CM-POS stimulated the growth of Lactobacillus and Bifidobacterium species, and induced them to produce short-chain fatty acids, and slightly suppressed immunoglobulin E production in U266 cells. Furthermore, pCO2-POS had higher angiotensin-converting enzyme inhibitory activity compared to CM-POS. This study suggests that pCO2 is a novel method for extracting pectin with unique molecular properties affecting POS functionality in vitro.

Screening and molecular dynamics simulation of ACE inhibitory tripeptides derived from milk fermented with Lactobacillus delbrueckii QS306.

Peptides in milk fermented with Lactobacillus delbrueckii QS306 before and after ultrahigh pressure treatment were identified using proteomics. Subsequently, 16 stable tripeptides were screened out based on activity score prediction, PeptideCutter analysis, and hydrophobicity calculations. Among them, WRP, WSR, and YRP showed the best angiotensin-converting enzyme (ACE) inhibitory activity, and their semi-inhibitory concentrations were 46.707, 300.121, and 89.555 μM, respectively. WRP and WSR were competitive inhibitors, whereas YRP was non-competitive. Gastrointestinal simulation revealed that WRP and YRP had better gastrointestinal stability. The values of RMSD, ΔGbind, ΔGpol, and RSMF obtained from molecular dynamics simulation indicated that the interaction of WRP and ACE was stable. Thus, Lactobacillus delbrueckii QS306-fermented milk can serve as an important source of ACE inhibitory peptides both before and after ultrahigh pressure treatment. The strategy of in silico screening, activity evaluation, and molecular dynamics simulation adopted in this study can be applied to the large-scale screening of novel peptides with high ACE inhibitory activity.

Metabolite profiling of fermented milks as affected by adjunct cultures during long-term storage

The effects of starter strains (Lactiplantibacillus plantarum 156, Lactobacillus casei ATCC 334, Lactobacillus helveticus DPC 4571, and Streptococcus thermophilus 20S4) on the physicochemical and microbiological properties, volatiles, bioactive peptides, and gamma-aminobutyric acid (GABA) contents of fermented milks were evaluated during storage. The use of different adjunct culture combinations had no significant effect on the gross chemical composition. The bacterial strains remained highly viable in the fermented milk during storage. The peptide extracts exhibited a high ACE-inhibitory activity, which was particularly increased in the samples where L. casei ATCC 334 and L. helveticus DPC 4571 strains co-existed. Almost the same levels of antioxidant activity was observed in the peptides extracted from fermented milk. Peptide extracts showed a certain level of antimicrobial activitiy against Staphylococcus aureus ATCC 29213, Listeria monocytogenes ATCC 7644, Salmonella Typhimurium RSHMB 95091, and Escherichia coli O157:H7; however, no inhibitory activity was observed against Bacillus cereus BC 6230. Among the free amino acids, His, Arg, Ala, and Pro were predominant in the samples. Significant differences were observed between samples regarding GABA content, which increased with increasing levels of proteolytic activity. A total of 33 volatile compounds were identified in fermented milks, with acetone, 2,3-butanedione, acetoin, 2-heptanone, acetic and hexanoic acids being the predominant volatiles. These results demonstrate the multifunctional role of peptides and GABA extracted from fermented milk through the action of specific Lactobacillus strains. Therefore, such a functional fermented milk product can be used to reduce the risk of disease or improve specific physiological functions.

Two novel angiotensin I-converting enzyme inhibitory peptides from garlic protein: In silico screening, stability, antihypertensive effects in vivo and underlying mechanisms

This study aimed to screen novel angiotensin I-converting enzyme (ACE) inhibitory peptides from garlic proteins and to explore their underlying antihypertensive mechanisms in vivo. After simulated hydrolysis and in silico screening, two novel peptides (MGR and HDCF) were obtained with the highest ACE inhibitory activity (IC50 of 4.50 μM and 26.38 μM) and acted as competitive inhibitors. They interacted with key residues in the ACE receptor mainly through hydrogen bonding and exhibited excellent stability against high temperature, extreme pH, and gastrointestinal digestion. In spontaneously hypertensive rats, MGR and HDCF effectively lowered blood pressure after single or continuous treatments. This was mainly achieved by balancing the renin-angiotensin system, improving renal and cardiac impairment, and regulating endothelial dysfunction. These findings suggested that garlic proteins were potentially suitable materials to prepare ACE inhibitory peptides and provided two promising candidates for ACE inhibition as functional food ingredients.

Buffalo yogurt fermented with commercial starter and Lactobacillus plantarum originating from breast milk lowered blood pressure in pregnant hypertensive rats

Nutritional therapy, which may have advantages over medication, is being investigated as a novel treatment for pregnancy-induced hypertension. Several studies have shown that probiotic yogurt supplementation during pregnancy has beneficial effects on maternal and fetal health. In this study, fermented buffalo milk was produced with yogurt culture and Lactobacillus plantarum B, a probiotic isolated from healthy breast milk with high angiotensin-converting enzyme inhibitory activity. The fermentation conditions under which the angiotensin-converting enzyme (ACE) inhibitory activity reached 84.51% were optimized by the response surface method as follows: 2 × 106 cfu/mL of L. plantarum B, yogurt culture 2.5 × 105 cfu/mL, and 8 h at 37°C. The distribution of ACE inhibitory peptides from fermented buffalo milk and fermented cow milk were further analyzed by liquid chromatography-mass spectrometry. By searching according to the structural features of ACE inhibitory peptides, 29 and 11 peptides containing ACE inhibitory peptide features were found in fermented buffalo milk and fermented cow milk, respectively. To investigate the in vivo antihypertensive activity of fermented buffalo milk, 18 pregnant rats were divided into 3 groups (n = 6 in each group) and administered 10 mL of normal saline, yogurt (20 mg/kg), or labetalol hydrochloride (4 mg/kg) daily from the beginning of pregnancy to parturition. To induce hypertension, methyl nitrosoarginine (125 mg/kg) was injected subcutaneously every day from d 15 of pregnancy to the day of delivery. Blood pressure was not significantly changed in the yogurt and labetalol groups after induction of hypertension and was lower compared with the normal saline group, but there was no difference between the yogurt and labetalol groups. This implied that the buffalo yogurt had a preventive and antihypertensive effect in the pregnancy-induced hypertensive rat model. Further studies to determine the mechanism of action, as well as a randomized control trial, are warranted.

A novel angiotensin-converting enzyme (ACE) inhibitory peptide from tilapia skin: Preparation, identification and its potential antihypertensive mechanism

To obtain food-derived peptides with high ACE inhibitory activity, tilapia skin was pretreated with steam explosion prior to enzymatic hydrolysis. The results showed that steam explosion pretreatment improved the hydrolysis efficiency and ACE inhibitory activity of fish skin hydrolysates. A novel ACE inhibitory peptide VGLFPSRSF (1009.17 Da) was obtained from steam-exploded fish skin hydrolysates. VGLFPSRSF had an IC50 value of 61.43 μM for ACE inhibitory activity, showing a non-competitive binding mode and gastrointestinal enzyme hydrolysis resistance. Molecular docking results showed that VGLFPSRSF interacted with ACE receptor protein through hydrogen bonding and hydrophobic interactions. Based on the results of network pharmacological analysis and molecular docking, VGLFPSRSF might regulate blood pressure through interaction with hypertensive targets such as AKT1, ACE, CD4, REN, and MMP9. Steam-exploded tilapia skin peptides had potential antihypertension activity and might be promising to achieve high-value utilization of fish skin by-products.

Production, identification, in silico analysis, and cytoprotection on H2O2-induced HUVECs of novel angiotensin-I-converting enzyme inhibitory peptides from Skipjack tuna roes.

Exceeding 50% tuna catches are regarded as byproducts in the production of cans. Given the high amount of tuna byproducts and their environmental effects induced by disposal and elimination, the valorization of nutritional ingredients from these by-products receives increasing attention. This study was to identify the angiotensin-I-converting enzyme (ACE) inhibitory (ACEi) peptides from roe hydrolysate of Skipjack tuna (Katsuwonus pelamis) and evaluate their protection functions on H2O2-induced human umbilical vein endothelial cells (HUVECs). Protein hydrolysate of tuna roes with high ACEi activity was prepared using flavourzyme, and ACEi peptides were isolated from the roe hydrolysate using ultrafiltration and chromatography methods and identified by ESI/MS and Procise Protein/Peptide Sequencer for the N-terminal amino acid sequence. The activity and mechanism of action of isolated ACEi peptides were investigated through molecular docking and cellular experiments. Four ACEi peptides were identified as WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12), respectively. The affinity of WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) with ACE was -8.590, -9.703, -9.325, and -8.036 kcal/mol, respectively. The molecular docking experiment elucidated that the significant ACEi ability of WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) was mostly owed to their tight bond with ACE's active sites/pockets via hydrophobic interaction, electrostatic force and hydrogen bonding. Additionally, WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) could dramatically elevate the Nitric Oxide (NO) production and bring down endothelin-1 (ET-1) secretion in HUVECs, but also abolish the opposite impact of norepinephrine (0.5 μM) on the production of NO and ET-1. Moreover, WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) could lower the oxidative damage and apoptosis rate of H2O2-induced HUVECs, and the mechanism indicated that they could increase the content of NO and activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to decrease the generation of reactive oxygen species (ROS) and malondialdehyde (MDA). WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) are beneficial ingredients for healthy products ameliorating hypertension and cardiovascular diseases.

Angiotensin I-Converting Enzyme-Inhibitory Activity and Phytochemical Profile of Constituents of the Leaves of Rehmannia glutinosa f. hueichingensis.

The root of Rehmannia glutinosa Liboschitz forma hueichingensis HSIAO has been used as a tonic and treatment for urinary and skin disorders in Japanese Kampo medicine. Phytochemical investigation of the root has been well reported, but that of the leaves is limited. To explore the potential value of R. glutinosa leaves, we focused on the angiotensin I-converting enzyme (ACE)-inhibitory activity. The leaf extract exhibited ACE-inhibitory activity, and the inhibitory potency of leaves was stronger than that of roots. Using this activity as an indicator, we isolated linaride (1), 6-O-hydroxybenzoyl ajugol (2), acteoside (3), leucosceptoside A (4), martynoside (5), luteolin (6), apigenin (7), and chrysoeriol (8) by separating and purifying the extract. We then examined the ACE-inhibitory activities of 1-8, catalpol (9), aucubin (10), ajugol (11), and echinacoside (12). Among them, 3, 6, and 12 displayed the most potent inhibitory activity. A simultaneous analytical method was also developed using compounds contained in R. glutinosa leaves and roots, and their contents were compared. The method consisted of extraction with 50% aqueous methanol under sonication for 60 min and LC/MS measurement. R. glutinosa leaves tended to have higher levels of majority of the analytes than the roots, including 3 and 6, which had higher ACE-inhibitory activity. These results suggest that 3 and 6 contribute to the ACE-inhibitory activity of R. glutinosa leaves, which may represent a useful medicinal resource for hypertension.

Probiotic, technological and health-related characteristics of lactobacilli isolated from breast milk.

Isolation and characterisation of lactobacilli from human milk and determination of their probiotic, technological and in vitro health-promoting properties with a view to their potential use in food fermentation. Seven lactobacilli isolates were obtained from human milk and identified as Lacticaseibacillus paracasei (isolates BM1-BM6) and Lactobacillus gasseri (BM7). The isolates were examined in vitro for their technological, probiotic and health-promoting potential. Overall, all isolates showed important technological properties based on the ability to grow in milk whey, a high to moderate acidification capacity and the absence of undesirable enzymatic activities. L. gasseri (BM7) differed from the L. paracasei isolates by the absence of several glycosidases and the inability to ferment lactose. Isolates L. paracasei BM3 and BM5 produced exopolysaccharides (EPS) from lactose. All isolates showed probiotic potential as they were tolerant to simulated gastrointestinal conditions, had high cell surface hydrophobicity, had not acquired resistance to relevant antibiotics and had no virulence characteristics. All L. paracasei showed high antimicrobial activity against various pathogenic bacteria and fungi, while L. gasseri showed a narrower spectrum of antimicrobial activity. All isolates showed health-promoting potential in vitro, as evidenced by high cholesterol-lowering activity, high ACE inhibitory activity and marked antioxidant activity. All strains showed excellent probiotic and technological properties for use in lactic ferments. Lactobacilli are an important part of the microbial population in human milk. A more detailed characterisation of these bacteria can contribute to the understanding of their functional and health importance for infants and to the selection of new probiotic strains for the dairy industry.

Properties of ACE inhibitory peptides isolated from Sipunculus nudus L and a DSPE-PEG modification for sustained release anti-hypertension agent

The organism Sipunculus nudus L is a good resource for marine peptides because of its rich protein. However, the disadvantage of biological peptides is their short metabolic half-life, therefore, structural modification of peptides is necessary. In this research, the enzymatic hydrolysis of Sipunculus nudus L was performed using trypsin and then peptides were isolated and purified from the hydrolysates, four novel tripeptides were identified by LC-MS-MS as Ser-Arg-Pro (SRP, m/z = 358.39), Pro-Arg-Pro (PRP, m/z = 368.43), Arg-Pro-Ala (RPA, m/z = 342.39), and Lue-Pro-Lys (LPK, m/z = 356.46), their ACE inhibitory activity was investigated with IC50 value as following 0.046, 0.42, 0.97, and 6.54 mM, respectively. Because of its highest ACE inhibitory activity, SRP was further selected to modify the chemical structure for a sustained release agent DSPE-PEG-SRP. Compared with 7 h of free SRP, the release of DSPE-PEG-SRP in vitro was approximately 120 h. The ACE inhibition rate of SRP released from the synthetic product and the raw material SRP was almost the same, molecular docking demonstrated that ACE inhibitory activity was attributed to the formation of hydrogen bonds between SRP and ACE active sites. In conclusion, DSPE-PEG-SRP, a novel sustained release agent, has great potential and is expected to be further applied to treat hypertension.

Preparation and activity evaluation of angiotensin-I converting enzyme inhibitory peptides from protein hydrolysate of mulberry leaf.

Angiotensin-I converting enzyme (ACE) inhibitory peptides drew wide attention in the food industry because of their natural reliability, non-toxicity, and safety. However, the characteristics of ACE inhibitory peptides obtained from protein hydrolysate of mulberry leaf prepared by Flavourzyme were still unclear. Based on the single-factor test, the Plackett-Burman test and response surface test were used to determine the key factors affecting the ACE inhibition rate in mulberry leaf protein hydrolysate and the optimum conditions of enzymatic hydrolysis. The results showed that the optimum technical parameters were as follows: the ratio of material to liquid is 1: 25 (w / v, g/mL), the Flavourzyme to substrate ratio was 3,000 U/g, the temperature of enzymatic hydrolysis was 50°C, pH was 6.3, and the time of enzymatic hydrolysis was 2.9 h. The ACE inhibitory peptides in the mulberry leaf protein hydrolysates were purified by ultrafiltration and gel filtration, aiming to obtain the highest active component. The 12 peptide sequences were identified by reverse liquid chromatography-mass spectrometry, and then, they were docked to the crystal structure of human angiotensin-I converting enzyme (1O8A), and the interaction mechanisms of 12 peptide sequences and 1O8A were analyzed. The docking results showed that among the 12 peptide sequences, ERFNVE (792.37 Da), TELVLK (351.72 Da), MELVLK (366.72 Da), and FDDKLD (376.67 Da), all had the lowest docking energy, and inhibition constant. The chemosynthetic ERFNVE (IC50: 2.65 mg/mL), TELVLK (IC50: 0.98 mg/mL), MELVLK (IC50:1.90 mg/mL) and FDDKLD (IC50:0.70 mg/mL) demonstrated high ACE-inhibitory activity with competitive inhibition mode. These results indicated that the ACE-inhibiting peptides from mulberry leaf protein hydrolyzed (FHMP) had the potential activities to inhibit ACE and could be used as functional food or drugs to inhibit ACE. This work provides positive support for mining the biological activity of mulberry leaves in the treatment of hypertension.