ACE-inhibitory Activity Research Articles

Optimization of Extraction Process and Activity of Angiotensin-Converting Enzyme (ACE) Inhibitory Peptide from Walnut Meal.

In order to further realize the resource reuse of walnut meal after oil extraction, walnut meal was used as raw material to prepare polypeptide, and its angiotensin-converting enzyme (ACE) inhibitory activity was investigated. The ACE inhibitory peptides were prepared from walnut meal protein by alkaline solution and acid precipitation. The hydrolysis degree and ACE inhibition rate were used as indexes to optimize the preparation process by single-factor experiment and response surface method. The components with the highest ACE activity were screened by ultrafiltration, and their antioxidant activities were evaluated in vitro. The effect of gastrointestinal digestion on the stability of walnut peptide was analyzed by measuring molecular weight and ACE inhibition rate. The results showed that the optimal extraction conditions were pH 9.10, hydrolysis temperature 54.50 °C, and hydrolysis time 136 min. The ACE inhibition rate of walnut meal hydrolysate (WMH) prepared under these conditions was 63.93% ± 0.43%. Under the above conditions, the fraction less than 3 kDa showed the highest ACE inhibitory activity among the ACE inhibitory peptides separated by ultrafiltration. The IC50 value of scavenging ·OH free radical was 1.156 mg/mL, the IC50 value of scavenging DPPH free radical was 0.25 mg/mL, and the IC50 value of scavenging O2- was 3.026 mg/mL, showing a strong total reducing ability. After simulated gastrointestinal digestion in vitro, the ACE inhibitory rate of walnut peptide decreased significantly, but it still maintained over 90% ACE inhibitory activity. This study provides a reference for the application of low-molecular-weight walnut peptide as a potential antioxidant and ACE inhibitor.

Preparation, identification, and molecular docking of novel angiotensin-converting enzyme inhibitory peptides derived from rice-based distillers' spent cakes.

Rice-based distillers' spent cake (RDSC), a by-product of the Chinese liquor (Baijiu) industry, is a potential source of angiotensin-converting enzyme (ACE) inhibitory peptide. Since ACE plays a crucial role in controlling hypertension, inhibition of ACE has been widely emphasized. The ACE inhibitory active peptide derived from by-products of food has been recognized as a safer and cheaper inhibitor. Aimed to discover ACE-inhibiting active peptides in RDSC. Hydrolysis of RDSC by alcalase for 4 h followed by ultrafiltration yielded low-molecular-weight (< 3 kDa) fractions. Subsequently, a comprehensive method using a combination of liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) and LC-Q-Exactive-MS to identify the novel short peptides (3-5 amino acids residues; n = 7) and medium-sized peptides (more than 6 amino acids residues; n = 6). In vitro activity assay showed that the peptides KPFFPGL, GFPRPLL, GPPGVF, and VGK exhibited the highest activity with inhibitory concentration of 50% (IC50) of 11.63, 12.34, 19.55, and 33.54 μmol L-1. Molecular docking reveal that the active and inactive sites (Glu123, Asp121, Arg522, and Lys118) play important roles in enhancing the ACE inhibitory activity of peptides. Here we report a comprehensive method that effectively extracted and identified the bioactive peptides from RDSC. Four highly active novel peptides may be the most promising candidates for functional foods against hypertension, provide significant information for enhancing value of rice-based distilled by-products. © 2024 Society of Chemical Industry.

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.

Biological Activity Evaluation of Olive, Grape, and Fig at Various Mixing Ratios

Purpose: This study aimed to evaluate the antioxidation and enzymatic activity-related qualities of four mixtures prepared with different mixing ratios of olives (O), grapes (V), and figs (F), which are representative ingredients of the Mediterranean diet. Methods: Following mixtures were prepared: olives–figs (OF), grapes–figs (VF), and olives–grapes–figs (OVF). For mixture preparation, the ingredients were mixed in following ratios: olives-to-grapes, olives-to-figs, and grapes-to-figs at ratios of 1:1 (30 g of each) as well as olives-to-grapes-to-figs at a ratio of 1:1:1 (20 g of each). The antioxidant (total polyphenol and flavonoid contents along with 2,2-diphenyl-1-picrylhydrazyl [DPPH] and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) [ABTS] radical scavenging) and enzymatic (α-glucosidase inhibitory and angiotensin-converting enzyme [ACE] inhibitory) activities of the four aforementioned mixtures were measured. Results: OV and OVF mixtures showed the highest total polyphenol (27.25±0.22 mg TAE/g) and flavonoid contents (27.9 ± 2.14 mg QE/g), respectively. DPPH radical scavenging ability was highest in OV (92.86 ± 0.17%). The highest ABTS radical scavenging activity was registered in the OVF mixture (42.88±1.19%). α-glucosidase and ACE inhibitory activity measurements were highest in the OVF mixture (79.75±0.15% and 88.61±0.08%, respectively). Conclusion: Highest physiological activity levels (i.e., anti-oxidation and enzymatic activity) were observed in the olive, grape, and fig (1:1:1) mixture, hence, its regular consumption could improve metabolic syndrome.

Changes in potato peptide bioactivity after gastrointestinal digestion. An in silico and in vitro study of different patatin-rich potato protein isolate matrices

Potato protein has gained attention as a promising protein source, because of its amino acid profile and technological functionality; however, little is reported about its nutritional properties as a function of processing history. In this work, the digesta of the four potato protein matrices (suspension, foam, gel, and heated foam) were analyzed by LC-MS/MS and their bioactivity evaluated in vitro and in silico.Different treatments significantly influenced digestion efficiency and peptide distribution. Heat treatment enhanced the hydrolysis, which led to distinct peptide patterns and distributions compared to unheated proteins. Heated foams showed smallest concentration of residual protein in the intestinal stage, and the highest resistance to digestion. Peptides obtained after digestion exhibited a range of potential health benefits in silico, namely, antimicrobial, antihypertensive, and antioxidant activities. All intestinal digesta showed in vitro DPPH radical scavenging and ACE-inhibitory activity.

Rice dreg protein as a high‐quality plant‐based protein resource: Characterization of structural, functional, and in vitro digestive properties

AbstractBackground and ObjectivesRice dregs, a by‐product of the process of making sugar from broken rice, have a protein content of up to 70%. However, rice dreg protein (RDP) has not yet been fully utilized due to its high‐temperature liquefaction denaturation during sugar production. In this study, the structural, functional, and in vitro digestive properties of rice protein (RP) extracted from broken rice and RDP derived from rice dregs were compared, with a view to providing a basis for further utilization of RDP.FindingsAlthough RDP was a heat‐denatured protein, it was found to have relatively better functional properties and a well‐balanced amino acid composition. Structural analysis results revealed that RDP showed a looser and disordered structure. However, SDS‐PAGE results showed that the subunit composition of the two proteins was similar. The in vitro simulated digestion results showed that the digests of RDP had higher antioxidant and ACE inhibitory activity, but RDP showed significantly lower digestibility than RP.ConclusionsThrough relevant modifications of RDP, RDP has the potential to be a good source of high‐quality protein in the human diet as the demand for plant‐based protein increases.Significance and NoveltyThis study can provide a basic theoretical basis for further development and utilization of RDP, which is also of great practical significance for seeking new plant protein resources and increasing the added value of broken rice.

Antioxidant and Angiotensin-Converting Enzyme Inhibitory Activity of Faba Bean-Derived Peptides After In Vitro Gastrointestinal Digestion: Insight into Their Mechanism of Action.

Faba bean flour, after in vitro gastrointestinal digestion, showed important antioxidant and angiotensin-converting enzyme (ACE) inhibitory activities. In the present study, 11 faba bean- derived peptides were synthesized to confirm their bioactivities and provide a deeper understanding of their mechanisms of action. The results revealed that 7 peptides were potent antioxidants, namely, NYDEGSEPR, TETWNPNHPEL, TETWNPNHPE, VIPTEPPH, VIPTEPPHA, VVIPTEPPHA, and VVIPTEPPH. Among them, TETWNPNHPEL had the highest activity in the ABTS (EC50 = 0.5 ± 0.2 mM) and DPPH (EC50 = 2.1 ± 0.1 mM) assays (p < 0.05), whereas TETWNPNHPE had the highest activity (p < 0.05) in the ORAC assay (2.84 ± 0.08 mM Trolox equivalent/mM). Synergistic and/or additive effects were found when selected peptides (TETWNPNHPEL, NYDEGSEPR, and VVIPTEPPHA) were combined. Four peptides were potent ACE inhibitors, where VVIPTEPPH (IC50 = 43 ± 1 μM) and VVIPTEPPHA (IC50 = 50 ± 5 μM) had the highest activity (p < 0.05), followed by VIPTEPPH (IC50 = 90 ± 10 μM) and then VIPTEPPHA (IC50 = 123 ± 5 μM) (p < 0.05). These peptides were noncompetitive inhibitors, as supported by kinetic studies and a molecular docking investigation. This study demonstrated that peptides derived from faba beans have multifunctional bioactivities, making them a promising food-functional and nutraceutical ingredient.

Assessment of the antioxidant and ACE-inhibitory activities and some quality characteristics of Kaşar cheese produced by probiotic Lactobacillus acidophilus

In this study, four types of Kaşar cheese were produced using raw milk (C), starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) (S), starter culture + probiotic Lactobacillus acidophilus ATCC 4356 (SLA), and probiotic L. acidophilus ATCC 4356 (LA) were produced and ripened at 6 ± 2 °C for 150 days. The physicochemical, microbiological, proteolysis, electrophoretic (Urea-PAGE), ACE-inhibitory, and antioxidant activity analyses of vacuum-packed Kaşar cheeses were performed on 5, 30, 60, 90, 120, and 150 days of ripening. During ripening, no significant differences (p > 0.05) were detected in total solids, fat, and protein values of Kaşar cheeses. Titratable acidity, water-soluble nitrogen (WSN), ripening index (RI), and electrophoresis results of cheese samples showed an increase while pH values decreased. Also, the degradation products of αs1-casein were higher than those of β-casein. The number of probiotic L. acidophilus ATCC 4356 after scalding decreased by an average of 1.57 log cfu/g. However, probiotic bacteria count increased during ripening and maintained their viability. The addition of L. acidophilus ATCC 4356 improved the bioactivity, electrophoresis, titratable acidity, and ripening index results of Kaşar cheese. ACE-inhibitory activity of Kaşar cheeses increased during ripening and had the highest value on the 150th day of ripening. Furthermore, antioxidant activity of Kaşar cheeses increased on the 60th day of ripening and then decreased. Consequently, the combination of probiotic bacteria and starter culture had a positive effect on the physicochemical, microbiological, and proteolytic properties of Kaşar cheese.

Antioxidant and angiotensin converting enzyme inhibitory activities of red lionfish (Pterois volitans L.) muscle protein hydrolysates obtained using pepsin-pancreatin system

Despite being an invasive species and representing a threat in the area, red lionfish (Pterois volitans L.) meat is valued for its pleasant taste and high protein content. The objective of the present work was to evaluate the angiotensin converting enzyme inhibition (ACE-I) and the antioxidant activities of red lionfish muscle protein hydrolysates in vitro. Hydrolysates were obtained using the pepsin-pancreatin system, and their degree of hydrolysis (DH), electrophoretic, and amino acid profile were determined. Subsequently, their ACE-I and ABTS+ radical scavenging activity were evaluated, selecting those with the highest response. The highest DH (66.1%) was found in the hydrolysate obtained at 120 min of reaction time (H120); electrophoresis revealed the action of the enzymes on the muscle proteins. The highest bioactivities occurred during hydrolysis with pepsin for 60 min (H60), obtaining the highest ACE-I of 68.8% (evaluated with 500 µg protein) with a DH of 16.8%, ACE-I related amino acid content of 33.6%, and hydrophobic amino acid content of 42.9%. With the 30 min hydrolysates (H30), the highest Trolox equivalent antioxidant capacity of 60.3 mM/mg protein was obtained with 18.4% DH and 22.1% radical scavenger amino acids; its comparison with H120 proved that higher DH did not produce a greater response in ABTS+ radical scavenging activity, DPPH, reducing power, and copper chelation assays; with β-carotene bleaching being the exception. Therefore, it can be concluded that red lionfish muscle hydrolysates could be a promising source of peptides with antihypertensive and antioxidant properties, and can be suitable as functional ingredients.

The novel angiotensin-I-converting enzyme inhibitory peptides from Scomber japonicus muscle protein hydrolysates: QSAR-based screening, molecular docking, kinetic and stability studies

Food-derived angiotensin-converting enzyme-inhibitory (ACE-I) peptides have attracted extensive attention. Herein, the ACE-I peptides from Scomber japonicus muscle hydrolysates were screened, and their mechanisms of action and inhibition stability were explored. The quantitative structure–activity relationship (QSAR) model based on 5z-scale metrics was developed to rapidly screen for ACE-I peptides. Two novel potential ACE-I peptides (LTPFT, PLITT) were predicted through this model coupled with in silico screening, of which PLITT had the highest activity (IC50: 48.73 ± 7.59 μM). PLITT inhibited ACE activity with a mixture of non-competitive and competitive mechanisms, and this inhibition mainly contributed to the hydrogen bonding based on molecular docking study. PLITT is stable under high temperatures, pH, glucose, and NaCl. The zinc ions (Zn2+) and copper ions (Cu2+) enhanced ACE-I activity. The study suggests that the QSAR model is effective in rapidly screening for ACE-I inhibitors, and PLITT can be supplemented in foods to lower blood pressure.

Optimization of Ultrasound Treatment for Watermelon Vinegar Using Response Surface Methodology: Antidiabetic—Antihypertensive Effects, Bioactive Compounds, and Minerals

Watermelon vinegar is a traditional fermented product with antioxidant activity. This study aimed to investigate the antihypertensive and antidiabetic properties of watermelon vinegar treated through ultrasound using the RSM method. We also evaluated the antioxidant activity (CUPRAC and DPPH), bioactive content (total phenolics and total flavonoids), mineral composition, phenolic compounds, α-glucosidase inhibition %, ACE inhibition %, of optimized, and α-amylase inhibition % during 24 months of storage of optimized watermelon vinegar. Optimized antidiabetic and antihypertensive activity was achieved at 6.7 min and 69% amplitude. The optimization of gallic acid was the dominant phenolic in the optimized ultrasound-treated watermelon vinegar (UT-WV) and showed a significant decrease during the 24 months of storage. The lycopene content of the UT-WV concentrate was 8.36 mg/100 mL, 8.30 mg/100 mL, 7.66 mg/100 mL, and 7.35 mg/100 mL after 0, 6, 2, and 24 months of storage, respectively. The levels of ACE inhibitory activity, α-glucosidase inhibitory activity, and α-amylase inhibitory activity decreased significantly (p &lt; 0.05) after 24 months of storage. K, with values of 201.03 ± 28.31, was the main mineral in the UT-WV. Therefore, the bioactive components and the antidiabetic and antihypertensive properties of the UT-WV produced by conventional fermentation were necessary. Therefore, further experimental studies are necessary for a better understanding of the possible and potential health effects of watermelon vinegar.

Novel Multitarget ACE Inhibitory Peptides from Bovine Colostrum Immunoglobulin G: Cellular Transport, Efficacy in Regulating Endothelial Dysfunction, and Network Pharmacology Studies.

In this study, we used traditional laboratory methods, bioinformatics, and cellular models to screen novel ACE inhibitory (ACEI) peptides with strong ACEI activity, moderate absorption rates, and multiple targets from bovine colostrum immunoglobulin G (IgG). The purified fraction of the compound proteinase hydrolysate of IgG showed good ACEI activity. After nano-UPLC-MS/MS identification and in silico analysis, eight peptides were synthesized and verified. Among them, SFYPDY, TSFYPDY, FSWF, WYQQVPGSGL, and GVHTFP were identified as ACEI peptides, as they exhibited strong ACEI activity (with IC50 values of 104.7, 80.0, 121.2, 39.8, and 86.3 μM, respectively). They displayed good stability in an in vitro simulated gastrointestinal digestion assay. In a Caco-2 monolayer model, SFYPDY, FSWF, and WYQQVPGSGL exhibited better absorption rates and lower IC50 values than the other peptides and were thereby identified as novel ACEI peptides. Subsequently, in a H2O2-induced endothelial dysfunction (ED) model based on HUVECs, SFYPDY, FSWF, and WYQQVPGSGL regulated ED by reducing apoptosis and ROS accumulation while upregulating NOS3 mRNA expression. Network pharmacology analysis and RT-qPCR confirmed that they regulated multiple targets. Overall, our results suggest that SFYPDY, FSWF, and WYQQVPGSGL can serve as novel multitarget ACEI peptides.

Targeted Affinity Purification and Mechanism of Action of Angiotensin-Converting Enzyme (ACE) Inhibitory Peptides from Sea Cucumber Gonads.

Protein hydrolysates from sea cucumber (Apostichopus japonicus) gonads are rich in active materials with remarkable angiotensin-converting enzyme (ACE) inhibitory activity. Alcalase was used to hydrolyze sea cucumber gonads, and the hydrolysate was separated by the ultrafiltration membrane to produce a low-molecular-weight peptide component (less than 3 kDa) with good ACE inhibitory activity. The peptide component (less than 3 kDa) was isolated and purified using a combination method of ACE gel affinity chromatography and reverse high-performance liquid chromatography. The purified fractions were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the resulting products were filtered using structure-based virtual screening (SBVS) to obtain 20 peptides. Of those, three noncompetitive inhibitory peptides (DDQIHIF with an IC50 value of 333.5 μmol·L-1, HDWWKER with an IC50 value of 583.6 μmol·L-1, and THDWWKER with an IC50 value of 1291.8 μmol·L-1) were further investigated based on their favorable pharmacochemical properties and ACE inhibitory activity. Molecular docking studies indicated that the three peptides were entirely enclosed within the ACE protein cavity, improving the overall stability of the complex through interaction forces with the ACE active site. The total free binding energies (ΔGtotal) for DDQIHIF, HDWWKER, and THDWWKER were -21.9 Kcal·mol-1, -71.6 Kcal·mol-1, and -69.1 Kcal·mol-1, respectively. Furthermore, a short-term assay of antihypertensive activity in spontaneously hypertensive rats (SHRs) revealed that HDWWKER could significantly decrease the systolic blood pressure (SBP) of SHRs after intravenous administration. The results showed that based on the better antihypertensive activity of the peptide in SHRs, the feasibility of targeted affinity purification and computer-aided drug discovery (CADD) for the efficient screening and preparation of ACE inhibitory peptide was verified, which provided a new idea of modern drug development method for clinical use.

Effect of temperature and shear stress on properties of nanovesicles carrying hydrolyzed pollen protein

In this study, the effect of storage (65 °C, 24 h) and shear rates (2-100 s−1, 10 min) on the particle size, poly-dispersity index (PDI), encapsulation efficiency (EE), Angiotensin-converting enzyme (ACE) and DPPH radical inhibition, iron ion reduction ability and flow behavior of nanovesicles containing hydrolyzed bee pollen (produced by alcalase and pepsin) were evaluated. Nanoliposomes were coated by chitosan (0.2 % w/w). After storage at 65 °C, the size of the nanovesicles raised 2–2.5 folds while EE showed 5–8 % decline. ACE and DPPH radical inhibition activity were also decreased. After applying the shear stress, PDI was increased significantly (P<0.05), while EE of the nanoniosomes showed a drastic decline (P<0.05). Nanoliposomes and nanoniosomes exhibited decline in the ACE inhibitory and antioxidant activity. At low shear rates Newtonian-like and weak pseudo-plastic behavior of the chitosan-coated nanoliposomes were observed. The flow index (n), (k) and (R2) indicated the suitability of power law model for describing the flow characteristics.

Enzymatic Hydrolysis of Water Lentil (Duckweed): An Emerging Source of Proteins for the Production of Antihypertensive Fractions.

Water lentil (Duckweed), an emerging protein source, is a small floating aquatic plant with agronomic and compositional characteristics rendering it a potential source of bioactive peptides. However, enzymatic hydrolysis of duckweeds has only been carried out to assess the antioxidant and antimicrobial activities of the hydrolysates. The main objectives of this study were to perform enzymatic hydrolysis of duckweed powder utilizing several enzymes and to evaluate the final antihypertensive activity of the fractions. Duckweed powder was efficiently hydrolyzed by pepsin, chymotrypsin, papain and trypsin, with degree of hydrolysis ranging from 3% to 9%, even without prior extraction and concentration of proteins. A total of 485 peptide sequences were identified in the hydrolysates and only 51 were common to two or three hydrolysates. It appeared that phenolic compounds were released through enzymatic hydrolyses and primarily found in the supernatants after centrifugation at concentrations up to 11 mg gallic acid/g sample. The chymotryptic final hydrolysate, the chymotryptic supernatant and the papain supernatant increased the ACE inhibitory activity by more than 6- to 8-folds, resulting in IC50 values ranging between 0.55 to 0.70 mg peptides/mL. Depending on the fraction, the ACE-inhibition was attributed to either bioactive peptides, phenolic compounds or a synergistic effect of both. To the best of our knowledge, this was the first study to investigate the enzymatic hydrolysis of duckweed proteins to produce bioactive peptides with therapeutic applications in mind.

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.

Evaluation of antioxidant and ACE inhibitory peptides in rice bran protein hydrolysate using non‐targeted UHPLC‐QTOF‐IMS profiling, MALDI‐TOF‐TOF‐MS/MS, and molecular docking study

SummaryIn the present study, rice bran protein (RBP) from the PB1121 variety was hydrolysed using trypsin and subjected to non‐targeted IMS profiling to identify antioxidant and antihypertensive amino acids in the resulting RBP hydrolysates. The hydrolysate was then separated into three fractions using ultrafiltration, and each fraction was tested for antioxidant and ACE inhibitory activities. The ACE activity was assessed using the tripeptide hippuryl‐histidyl‐leucine (HHL) as a model peptide via HPLC‐DAD. The fraction with the molecular weight (&gt;3000 Da) displayed the strongest antioxidant and ACE inhibitory activity. This fraction was further divided into five fractions using gel Sephadex G‐25, and the greatest levels of antioxidant and ACE inhibitory activity were found in fraction F3B. Fraction F3B was then fractionated using HPLC, and the fraction with ACE inhibitory activity (IC50 of 43 mg mL−1) was analysed using MALDI‐TOF‐TOF mass spectrometry to determine its exact molecular mass and amino acid sequence. The amino acid sequence FMKSK (phe‐met‐lys‐ser‐lys) with a Mw of 655.376 Da was detected, and the molecular docking investigation revealed that FMKSK suppresses ACE by forming strong hydrogen bonds with the active pockets of human ACE. These findings suggest that rice bran contains bioactive peptides with antioxidant and ACE inhibitory effects, making it a promising raw material for the production of beneficial products.

A strategy to boost xanthine oxidase and angiotensin converting enzyme inhibitory activities of peptides via molecular docking and module substitution

Molecular docking and activity evaluation screened the dipeptide module GP with low xanthine oxidase (XOD) inhibitory activity and modules KE and KN with high activity, and identified them as low- and high-contribution modules, respectively. We hypothesized the substitution of low-contribution modules in peptides with high contributions would boost their XOD inhibitory activity. In the XOD inhibitory peptide GPAGPR, substitution of GP with both KE and KN led to enhanced affinity between the peptides and XOD. They also increased XOD inhibitory activity (26.4% and 10.3%) and decreased cellular uric acid concentrations (28.0% and 10.4%). RNA sequencing indicated that these improvements were attributable to the inhibition of uric acid biosynthesis. In addition, module substitution increased the angiotensin-converting enzyme inhibitory activity of GILRP and GAAGGAF by 84.8% and 76.5%. This study revealed that module substitution is a feasible strategy to boost peptide activity, and provided information for the optimization of hydrolysate preparation conditions.

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.

Lactic acid fermentation of kamaboko, a heated Alaska pollock surimi, enhances angiotensin I-converting enzyme inhibitory activity via fish protein hydrolysis.

To enhance the value of surimi, efforts have been made to develop a fermentation method with lactic acid bacteria (LAB) to proteolyze fish protein. However, fermenting unheated surimi poses a spoilage risk due to its high bacterial content. Surimi heat treatment can prevent spoilage, but gel formation induced by heating introduces another technical issue: it hinders uniform fermentation. Thus, this study aims to observe the proteolysis and enhance the functionality of seafood product through lactic acid fermentation of kamaboko, a heated surimi. Upon analyzing the kamaboko fermented with Lactobacillus helveticus JCM1004, we observed that LAB produced protease, resulting in the degradation of myosin heavy chain and actin during fermentation. Lactic acid fermentation significantly augmented the peptide content of kamaboko, subsequently elevating the angiotensin Ⅰ-converting enzyme (ACE) inhibitory activity in 200-fold diluted extract of fermented kamaboko to approximately 70% and higher. Notably, our investigation revealed that proteolysis was confined to the surface of kamaboko, as evidenced by SDS-PAGE analysis. This observation implies that the surface area of kamaboko influences the ACE inhibitory activity. Through a comparative analysis of various bacterial strains, we demonstrated that the increase in ACE inhibitory activity is contingent on the protease generated by LAB. These results suggest that LAB-mediated proteolysis of fish proteins liberates bioactive peptides, thereby manifesting in the ACE inhibitory activity. In summary, this study underscores that the fermentation of kamaboko employing proteolytic LAB holds promise in the development of novel functional seafood products.