ACE-inhibitory Activity Research Articles

Ameliorative effect of mussel-derived ACE inhibitory peptides on spontaneous hypertension rats.

The purpose of this study was to prepare the novel mussel-derived ACE inhibitory peptides (MEPs) by enzymatic hydrolysis of Mytilus edulis and investigate their antihypertensive effects in vivo. After assessing the stability of MEPs in vitro, we investigated the effect of MEPs on hypertension using spontaneously hypertensive rats (SHRs). Subsequently, MEPs were purified and identified by ultrafiltration, gel filtration chromatography and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Our study demonstrated that MEPs could keep stable ACE inhibitory activity after treatment with heat, acid, alkali, metal ions and simulated gastrointestinal digestive fluid. Additionally, the animal experiments showed that both short-term and long-term treatment with MEPs resulted in a significant reduction in systolic and diastolic blood pressure in SHRs. Mechanistically, the results suggested that MEPs could reduce vascular remodeling, regulate renin-angiotensin system (RAS), and inhibit kidney and myocardial fibrosis. Finally, we isolated and identified five peptides from MEPs, with the peptide Ile-Leu-Thr-Glu-Arg showed the highest ACE inhibition rate. Our findings demonstrate the potential use of MEPs as active components in functional foods designed to lower blood pressure.

Highly selective and pH responsive adsorption of ZIF-8 for angiotensin-converting enzyme (ACE) inhibitory active peptides and its mechanism

Searching adsorbents for high recognition and adsorption capacities of active peptides has become the hotspot of scientific research in the screening and purification of peptides. In this work, we selected MOFs materials with good biocompatibility to systematically investigated for the selective adsorption of highly active ACE inhibitory peptides. Herein, five typical kinds of metal organic frameworks (MOFs) were initially screened for their adsorption capacities towards di-peptide (CW) having ultra-high angiotensin-converting enzyme (ACE) inhibitory activity (IC50 = 0.16 μM). The effects of their pore sizes and surface potentials on CW adsorption capacity were explored in this work. Among these MOFs, ZIF-8 was chosen as a di-peptide adsorbent due to its excellent adsorption capacity of CW (0.382 mmol/g). Besides, the adsorption behavior of ZIF-8 for di-peptides in the mixed solution was systematically explored. Experimental results indicated that ZIF-8 exhibited highly specific adsorption towards CW while showing very low and almost non-adsorption for the two inactive peptides, DD and RR. In their ternary peptide solution (molar ratio: CW/DD/RR = 1/10/10) for simulated protein hydrolysate, ZIF-8 displayed ultra-high adsorption selectivity (α = 46.6) for CW and thus enhanced almost 70.9 times the ACE inhibitory activity for the enriched solution. Meanwhile, molecular simulation revealed that ZIF-8 had high recognition towards CW, which was primarily attributed to synergistic mechanisms of electrostatic attraction, NH/SH···π interaction, and pore size screening of ZIF-8 towards CW. Interestingly, ZIF-8 was discovered for the first time to have a distinct pH-responsive property towards CW enrichment. Based on this property, pH-responsive adsorption was carried out with desorption over ZIF-8, and a stable regeneration process for 5 continuous adsorption/desorption cycles was accomplished. Collectively, this work proved that MOFs have promising application prospects in the field of peptide adsorption.

Inhibitory effects of the anthocyanins from Lycium ruthenicum Murray on angiotensin-I-converting enzyme: in vitro and molecular docking studies.

Lycium ruthenicum Murray (LRM), a perennial shrub plant belonging to the Solanaceae family, is rich in anthocyanins, which have anti-inflammatory, antioxidant, lipid-lowering, intestinal flora regulating, and other pharmacological qualities. This study was primarily aimed to investigate the inhibitory effect of different anthocyanin purities from LRM on angiotensin-I-converting enzyme (ACE) activity in vitro. Moreover, the inhibitory mechanism was further analyzed by molecular docking technology. Two main anthocyanin isomers were identified by ultra-performance liquid chromatography-tandem mass spectrometry and proton/carbon-13 nuclear magnetic resonance, namely petunidin-3-O-[rhamnopyranosyl-(trans-p-coumaroyl)]-5-O-(β-d-glucopyranoside) (trans-Pt3R5G) and petunidin-3-O-[rhamnopyranosyl-(cis-p-coumaroyl)]-5-O-(β-d-glucopyranoside) (cis-Pt3R5G), with a molar ratio of 9:1. Three purification grades of Pt3R5G all showed excellent inhibitory effects on ACE, with the half maximal inhibitory concentration (IC50 ) values being 0.562, 0.421, and 0.106 mg·mL-1 . Increasing the purity may reduce the IC50 within a certain concentration range. An enzymatic kinetic experiment showed that the inhibitory effect of Pt3R5G on ACE was reversible and non-competitive: Pt3R5G and substrate were not in competition for the active sites of ACE. Molecular docking technology further revealed the possible mechanism was that Pt3R5G and ACE amino acid residues were interacting by hydrogen bonds to exert the inhibitory effect. The results indicated that Pt3R5G from LRM was highly effective at inhibiting ACE activity in vitro, with the hydrogen bonds of Pt3R5G and ACE amino acid residues exerting the inhibition. As a potential plant-based ACE inhibitor, Pt3R5G can be used as a functional ingredient for antihypertensive effects. © 2023 Society of Chemical Industry.

Comparison of Amino Acid Profile, ACE Inhibitory Activity, and Organic Acid Profile of Cow and Goat Yogurts Produced with Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12, and Classical Yogurt Culture.

In this study, we aimed to produce a standard, more functional, and nutritious yogurt by using 5 different combinations of cow milk and goat milk and 2 types of starter cultures (classical yogurt culture and commercial probiotic culture). It was determined that the use of different milk types and different starter cultures in yogurt production had a statistically very significant effect (P < 0.01) on all physicochemical, microbiological, and biochemical properties. In addition, the storage period was effective on all parameters examined at varying rates. In the context, the use of goat milk in the experimental yogurt samples caused an increase in the ACE inhibitory activity values and the count of S. thermophilus, while the use of cow milk caused an increase in serum separation and pH values. On the other hand, serum separation, pH values, and ACE inhibitory activity and phenylalanine and leucine levels were found to be higher in the yogurts produced by using ABT-2 probiotic culture. It was observed that an increase in the levels of asparagine, aspartic acid, proline, and serine, as well as lactic acid, orotic acid, and citric acid, is higher in the yogurts produced by using classical yogurt culture. It has been concluded that the combination of goat milk and cow milk at different proportions and the use of probiotic culture together in yogurt production can produce yogurt that is more functional and richer in terms of organic compounds and essential amino acids.

Production of marine bacterial metalloprotease A69 and evaluation of its potential in preparing soybean peptides with angiotensin-converting enzyme-inhibitory activity.

Marine bacteria secrete a variety of proteases, which are a good source to explore proteases with application value. However, only a few marine bacterial proteases with a potential in bioactive peptides preparation have been reported. The metalloprotease A69 from the marine bacterium Anoxybacillus caldiproteolyticus 1A02591 was successfully expressed in the food safe bacterium Bacillus subtilis as a secreted enzyme. A technique to efficiently produce protease A69 in a 15-L bioreactor was established, with a production of 8988 U mL-1 . Based on optimizing the hydrolysis parameters of A69 on soybean protein, a process for soybean protein peptides (SPs) preparation was set up, in which soybean protein was hydrolyzed by A69 at 4000 U g-1 and 60 °C for 3 h. The prepared SPs had a high content (> 90%) of peptides with a molecular mass less than 3000 Da and contained 18 amino acids. The prepared SPs showed high angiotensin-converting enzyme (ACE)-inhibitory activity, with an IC50 value of 0.135 mg mL-1 . Moreover, three ACE-inhibitory peptides, RPSYT, VLIVP and LAIPVNKP, were identified from the SPs using liquid chromatography-mass spectrometry analysis. The marine bacterial metalloprotease A69 has a promising potential for preparing SPs with good nutritional and potential antihypertensive effects, laying a good foundation for its industrial production and application. © 2023 Society of Chemical Industry.

Structure identification and inhibitory mechanism evaluation of three novel angiotensin converting enzyme (ACE) inhibitory peptides from small-aroma chicken

Small-aroma chicken with a high protein content, is widely distributed in the mountainous area of Yunnan-Guizhou Plateau, China. In this work, three novel ACE-inhibitory peptides, Leu-Thr-Glu-Lys-Val-Val-Phe (LTQKVVF), Leu-Asp-Asp-His-Phe-Leu (LDDHFL), and Val-Pro-Gly-Pro-Glu-Pro-Lys-Pro (VPGPEPKP), were prepared from the Small-Aroma Chicken breast. The purification and identification protocol employed comprised ion-exchange chromatography, gel filtration chromatography, reverse phase-high performance liquid chromatography (RP-HPLC), and nano liquid chromatography-electrospray ionization–tandem mass (Nano-LC-ESI–MS/MS). Compared with VPGPEPKP and VPGPEPKP, LTQKVVF displayed noticeable ACE inhibitory activity, with IC50 values of 189.34 μM. What’s more, the Lineweaver-Burk plots revealed peptides LTQKVVF and LDDHFL acted as the mixed-competitive inhibitor while VPGPEPKP inhibited ACE in a manner similar to uncompetitive inhibition. The binding free energies of LTQKVVF, LDDHFL, and VPGPEPKP for ACE were −8.1 kcal/mol, −8.6 kcal/mol, and −9.6 kcal/mol, respectively. The strong inhibition of ACE by VPGPEPKP may be attributed to the interaction of hydrogen bonds, alkyl, and pi-alkyl, which formed by crucial residues of ACE.

Comparison of camel, buffalo, cow, goat, and sheep yoghurts in terms of various physicochemical, biochemical, textural and rheological properties

Comparative physicochemical, biochemical, textural, and rheological properties of yoghurts produced using buffalo, camel, cow, goat, and sheep milk were analysed. The physicochemical, textural, and rheological properties were determined over a 14-day storage period. Different animal milk types had a significant effect on all physicochemical analyses, fatty acid composition, conjugated linoleic acid content, cholesterol content, all amino acids except asparagine, ACE inhibitory activity, citric acid, and orotic acid, as well as other textural and rheological properties, except flow index n parameter. The storage period had a very significant effect on titratable acidity, pH value, firmness, consistency, cohesiveness, and yield stress τ0 parameters. Compared with other yoghurts studied, camel yoghurt was richer in terms of myristic acid from saturated fatty acids, ∑PUFA, arginine, lysine, phenylalanine, tryptophan, valine from essential amino acids, glutamic acid, and proline from non-essential amino acids, ACE inhibitory activity value, and hippuric and orotic acids.

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.

Antioxidant and ACE-Inhibitory Activity of Protein Hydrolysates Produced from Atlantic Sea Cucumber (Cucumaria frondosa).

Atlantic sea cucumber is a benthic marine echinoderm found in Northwest Atlantic waters and is harvested mainly for its body wall. The body wall, along with internal organs and aquaphyrangeal bulb/flower, is a rich source of proteins, where the latter parts are often considered as processing discards. The objective of this research was to produce protein hydrolysates from sea cucumber tissues (body wall, flower, and internal organs) with bioactive properties associated with antioxidants, DNA and LDL cholesterol oxidation inhibition, and angiotensin-I-converting enzyme (ACE) inhibitory effects. The protein hydrolysates were prepared using food-grade commercial enzymes, namely Alcalase, Corolase, and Flavourzyme, individually and in combination, and found that the combination of enzymes exhibited stronger antioxidant potential than the individual enzymes, as well as their untreated counterparts. Similar trends were also observed for the DNA and LDL cholesterol oxidation inhibition and ACE-inhibitory properties of sea cucumber protein hydrolysates, mainly those that were prepared from the flower. Thus, the findings of this study revealed potential applications of sea cucumber-derived protein hydrolysates in functional foods, nutraceuticals, and dietary supplements, as well as natural therapeutics.

Angiotensin I-Converting Enzyme Inhibitory Activity of Two Peptides Derived from In Vitro Digestion Products of Pork Sausage with Partial Substitution of NaCl by KCl.

This study aimed to identify angiotensin I-converting enzyme (ACE) from in vitro digestion products of pork sausage with partial substitution of NaCl by KCl (PSRK). Peptides from in vitro digestion products of PSRK were identified through liquid chromatography with tandem mass spectrometry analysis coupled with de novo sequencing. Subsequently, the ACE inhibitory peptides LIVGFPAYGH and IVGFPAYGH were screened based on PeptideRanker, in silico absorption, molecular docking, and the determination of ACE inhibitory activity. In addition, the ACE inhibitory peptides LIVGFPAYGH and IVGFPAYGH were mixed-type inhibitors; these peptides' ACE inhibitory activities were expressed as the 50% inhibitory concentration (IC50) values in vitro, which were 196.16 and 150.88 μM, respectively. After 2 h of incubation, LIVGFPAYGH and IVGFPAYGH could be transported through Caco-2 cell monolayers with paracellular passive diffusion. Furthermore, LIVGFPAYGH and IVGFPAYGH significantly increased the levels of ACE2 and nitric oxide while decreasing the levels of ACE, angiotensin II, and endothelin-1 in Ang I-treated human umbilical vein endothelial cells, indicating the ACE inhibitory effect of LIVGFPAYGH and IVGFPAYGH. In summary, LIVGFPAYGH and IVGFPAYGH from PSRK can be used as functional foods with antihypertensive activity.

Utilization of edible coating based on quince seed mucilage loaded with thyme essential oil: Shelf life, quality, and ACE-inhibitory activity efficiency in Kaşar cheese

Edible coatings offer many advantages in cheese coating for prolonging the shelf life and improving quality properties. Mould spoilage that occurs during ripening is one of the most important issues in Kaşar cheese. The current study focused on the effects of an edible coating solution based on quince seed mucilage (QSM) containing thyme oil (TO) in different ratios, on the surface moulding of Kaşar cheese and evaluated the physicochemical, microbiological, textural, and proteolysis characteristics of Kaşar cheese throughout the 120 days of ripening. Also, the effect of edible coating on the in-vitro Angiotensin-converting enzyme (ACE)-inhibitory activities of pH 4.6-soluble extracts of Kaşar cheeses was investigated. Results showed that the coating of Kaşar cheese with QSM and the increased levels of thyme oil significantly suppress mould growth throughout the ripening. Until 120th days of ripening, counts of yeasts and moulds were lower <2 log cfu g−1 in coated cheese sample with QSM containing 2% TO. Coating with QSM caused an increase in moisture loss compared to vacuum-packed cheeses, however, didn't change the normal ripening conditions such as microbiological, chemical, textural, and proteolysis properties of Kaşar cheese. As the ripening progressed, ACE-inhibitory activity increased in all samples, with the highest inhibition in vacuum-packed and coated cheeses. Overall, it was determined that the QSM coating showed good potential as a coating material for the protection of cheese shelf life and quality as well as for enhancing ACE-inhibitory activity.

Effect of Ripening and In Vitro Digestion on Bioactive Peptides Profile in Ras Cheese and Their Biological Activities.

The effect of ripening and in vitro digestion on the biological activities, peptide profiles and release of bioactive peptides in Ras cheese has been investigated. Ras cheese ripening largely influenced the extent of protein hydrolysis. The advancement in ripening resulted in an increase in total peptides (from 0.97 to 2.46 mmol leucine/g in samples at 30 and 180 days of ripening, respectively) and bioactive peptides concentration, especially angiotensin-converting enzyme (ACE)-inhibitory, dipeptidyl-peptidase-IV-(DPP-IV)-inhibitory and antioxidant peptides. In vitro gastro-intestinal digestion further promoted protein hydrolysis and the release of bioactive peptides. Digested Ras cheese at 90 and 180 days of ripening displayed the highest bioactive peptides intensity. The variations in bioactive peptides amount during ripening and in vitro digestion were correlated with the changes in ACE-inhibitory, DPP-IV-inhibitory and antioxidant activities. The highest amounts of VPP and IPP were detected in digested Ras cheese at 90 days of ripening (17.44 and 36.50 mg/kg of cheese, respectively), whereas the highest concentrations of APFPE were found in undigested and digested 180-day ripened Ras cheese (82.09 and 52.01 mg/kg of cheese, respectively). The present investigation underlined potential differences in the biological effect after the ingestion of Ras cheese at different ripening times.

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.

Peptidomics Analysis Reveals the Buccal Gland of Jawless Vertebrate Lamprey as a Source of Multiple Bioactive Peptides.

Various proteins with antibacterial, anticoagulant, and anti-inflammatory properties have been identified in the buccal glands of jawless blood-sucking vertebrate lampreys. However, studies on endogenous peptides in the buccal gland of lampreys are limited. In this study, 4528 endogenous peptides were identified from 1224 precursor proteins using peptidomics and screened for bioactivity in the buccal glands of the lamprey, Lethenteron camtschaticum. We synthesized four candidate bioactive peptides (VSLNLPYSVVRGEQFVVQA, DIPVPEVPILE, VVQLPPVVLGTFG, and VPPPPLVLPPASVK), calculated their secondary structures, and validated their bioactivity. The results showed that the peptide VSLNLPYSVVRGEQFVVQA possessed anti-inflammatory activity, which significantly increased the expression of anti-inflammatory factors and decreased the expression of inflammatory factors in THP-1 cells. The peptide VVQLPPVVLGTFG showed antibacterial activity against some gram-positive bacteria. The peptide VSLNLPYSVVRGEQFVQA possessed good ACE inhibitory activity at low concentrations, but no dose-related correlation was observed. Our study revealed that the buccal glands of the jawless vertebrate lamprey are a source of multiple bioactive peptides, which will provide new insights into the blood-sucking mechanism of lamprey.

ACE-Inhibitory Activity of Whey Proteins Fractions Derived of Fermentation by Lacticaseibacillus rhamnosus GG and Streptococcus thermophilus SY-102.

Many studies have reported the benefits of probiotic microorganisms and the production of angiotensin-converting enzyme (ACE) inhibitors. Determining the proteolytic and ACE inhibition capacities during whey fermentation was the goal of the study. Lacticaseibacillus rhamnosus GG, Streptococcus thermophilus SY-102, and both bacteria together were initially inoculated into whey, reaching an initial concentration of 108 CFU per milliliter in each fermentation system. Through the use of TNBS, SDS-PAGE, and SEC-HPLC methods, the proteolytic profile was examined. An in vitro investigation was performed to test the ACE inhibition capacity. With S. thermophilus, the logarithmic phase of microbial development was shorter than with L. rhamnosus (6 and 12 h, respectively). The logarithmic phase in the co-culture fermentation, however, was extended to 24 h. There were no significant differences in pH between the fermentations. However, the co-culture had a greater concentration of protein hydrolysis (453 ± 0.06 μg/mL), as indicated by the amount of free amino groups. Similarly, this fermentation produced more low molecular weight peptides. The higher inhibition activity, which increased at the conclusion of the fermentation with the co-culture and reached 53.42%, was influenced by the higher peptide synthesis. These findings highlighted the significance of creating useful co-culture products.

Effect of ohmic heating in bioactive peptides, volatile compounds, and fatty acid profile in a high-protein vanilla flavoured milk drink

High-protein vanilla flavoured milk was processed using ohmic heating (OH) at 60 Hz and 60, 80, 100 and 120 V (5.22, 6.96, 8.70 and 10.43 V cm−1, respectively), coded as OH60, OH80, OH100, and OH120, respectively. Peptide, volatile compounds, and fatty acids profiles were compared with untreated and pasteurised samples. Pasteurisation or OH resulted in loss of a β-casein peptide fraction with ACE-inhibitory activity, volatile compounds (1-pentanol, cyclohexanol, isobutyl butyrate, and ethyl decanoate), and fatty acids. However, OH processing released desirable volatile compounds (acetaldehyde, α-phellandrene). The application of intermediate electric field strengths (OH100) resulted in forming of a β-casein peptide with ACE-inhibitory activity and desirable volatile compounds (acetic acid, 2-pentanone, and 3-methyl-1-butanol), while maintaining butyric acid concentration and monounsaturated and polyunsaturated fatty acid levels more similar to the untreated product. The results suggest that OH, mainly at 10.43 V cm−1, is a promising technology in the development of milk drinks.

INVESTIGATION OF CHANGES IN SOME BIOACTIVE PROPERTIES OF PHENOLIC EXTRACTS FROM PULP AND SEED TISSUES OF ZIZIPHUS JUJUBA DURING IN VITRO DIGESTION

In this study, changes in angiotensin-I converting enzyme (ACE) inhibitory, α-amylase inhibitory and antioxidant activities, total phenolic content (TPC), total monomeric anthocyanin content (TMAC) of ultrasonic phenolic extracts from pulp and seed of Ziziphus jujuba were investigated during in vitro digestion. Bioaccessible fractions of phenolics in seed and pulp extracts were calculated as 23.24±4.46% and 9.43±0.24%, respectively. Moreover, bioaccessibility for TMAC in seed extracts (147.83±9.20%) was higher than pulp (15.76±3.89%) (P&amp;lt;0.05). A decrease in the antioxidant activity of the extracts occurred after in vitro digestion (P&amp;lt;0.05). The ACE inhibitory activity of undigested extracts from seed (86.04±0.00%) was higher than that of the undigested pulp extract (42.74±8.57%) (P&amp;lt;0.05). The α-amylase inhibitory activity of seed and pulp extracts was determined as 49.18±0.35% and 36.07±5.83%, respectively. The results of the study showed that ACE inhibitory activity and α-amylase inhibitory activity of the polyphenolics from pulp increased after in vitro digestion.

Screening potential hypertensive peptides using two consecutive bioassay-guided SPE fractionations and identification of an ACE inhibitory peptide, DHSTAVW (DW7), derived from pearl garlic protein hydrolysate

The pearl garlic (Allium sativum L.) protein (PGP) was digested using pepsin, trypsin, α-chymotrypsin, thermolysin, and simulated gastrointestinal digestion. The α-chymotrypsin hydrolysate showed the highest angiotensin-I-converting enzyme inhibitory (ACEI) activity, with an IC50 value of 190.9 ± 11 µg/mL. A reversed-phase C18 solid-phase extraction (RP-SPE) cartridge was used for the first fractionation, and the S4 fraction from RP-SPE showed the most potent ACEI activity (IC50 =124.1 ± 11 3 µg/mL). The S4 fraction was further fractionated using a hydrophilic interaction liquid chromatography SPE (HILIC-SPE). The H4 fraction from HILIC-SPE showed the highest ACEI activity (IC50 =57.7 ± 3 µg/mL). Four ACEI peptides (DHSTAVW, KLAKVF, KLSTAASF, and KETPEAHVF) were identified from the H4 fraction using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and their biological activities were appraised in silico. Among the identified α-chymotryptic peptides, DHSTAVW (DW7), derived from I lectin partial protein, exhibited the most potent ACEI activity (IC50 value of 2.8 ± 0.1 µM). DW7 was resistant to simulated gastrointestinal digestion, and it was classified as a prodrug-type inhibitor according to the preincubation experiment. The inhibition kinetics indicated that DW7 was a competitive inhibitor, which was rationalized by the molecular docking simulation. The quantities of DW7 in 1 mg of hydrolysate, S4 fraction, and H4 fraction were quantified using LC-MS/MS to give 3.1 ± 0.1, 4.2 ± 0.1, and 13.2 ± 0.1 µg, respectively. The amount of DW7 was significantly increased by 4.2-fold compared with the hydrolysate, which suggested that this method is efficient for active peptide screening.

Investigating structure, biological activity, peptide composition and emulsifying properties of pea protein hydrolysates obtained by cell envelope proteinase from Lactobacillus delbrueckii subsp. bulgaricus

We present the structure, biological activity, peptide composition, and emulsifying properties of pea protein isolate (PPI) after hydrolysis by cell envelope proteinase (CEP) from Lactobacillus delbrueckii subsp. bulgaricus. Hydrolysis resulted in the unfolding of the PPI structure, characterized by an increase in fluorescence and UV absorption, which was related to thermal stability as demonstrated by a significant increase in ΔH and the thermal denaturation temperature (from 77.25 ± 0.05 to 84.45 ± 0.04 °C). The hydrophobic amino acid of PPI significantly increased from 218.26 ± 0.04 to 620.77 ± 0.04 followed by 557.18 ± 0.05 mg/100 g, which was related to their emulsifying properties, with the maximum emulsifying activity index (88.62 ± 0.83 m2/g, after 6 h hydrolysis) and emulsifying stability index (130.77 ± 1.12 min, after 2 h hydrolysis). Further, the results of LC-MS/MS analysis demonstrated that the CEP tended to hydrolyze peptides with an N-terminus dominated by Ser and a C-terminus dominated by Leu, which enhanced the biological activity of pea protein hydrolysates, as supported by their relatively high antioxidant (ABTS+ and DPPH radical scavenging rates were 82.31 ± 0.32% and 88.95 ± 0.31%) and ACE inhibitory (83.56 ± 1.70%) activities after 6 h of hydrolysis. 15 peptide sequences (score > 0.5) possessed both antioxidant and ACE inhibitory activity potential according to the BIOPEP database. This study provides theoretical guidance for the development of CEP-hydrolyzed peptides with antioxidant and ACE inhibitory activity that can be used as emulsifiers in functional foods.

High accuracy prediction of dipeptide angiotensin-converting enzyme (ACE) inhibitory activity by improving the credibility of the 3D-quantitative structure-activity relationship (3D-QSAR) model database and investigating inhibition mechanism

The 3D-QSAR model is one of the most effective techniques for predicting the peptide bioactivity based on their structure properties. The accuracy of model prediction is highly dependent on the bio-activity of the peptides in its dataset. However, the same peptide used for constructing the database was reported to have obviously different activities in different published articles, which may significantly decrease the prediction accuracy. Based on this, we chose ACE inhibitory (ACE-I) dipeptides that can be absorbed directly into the human small intestine as research object. Ten dipeptides were randomly selected from the literatures for molecular docking with ACE and synthesized to test their activity. Ultimately, a linear equation was developed between bio-activities and docking scores, which was used to revalidate the reliable ACE-I activities of all reported dipeptides for constructing a credible dataset of 3D-QSAR model. The prediction accuracy was significantly enhanced and the model we established had a high Q2 = 0.840 and R2 = 0.998. Furthermore, dipeptide CW was predicted and tested in vitro to achieve the highest ACE-I activity (IC50 = 0.16 μM), and the inhibition mechanism was also investigated. This study introduced a new method for predicting bio-activity with high precision using the 3D-QSAR model.