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Food-derived angiotensin-I-converting enzyme (ACE)-inhibitory peptides have gained attention for their potent and safe treatment of hypertensive disorders. However, there are some limitations of conventional methods for preparing ACE-inhibitory peptides. In this study, in silico hydrolysis, the quantitative structure–activity relationship (QSAR) model, LC-MS/MS, inhibition kinetics, and molecular docking were used to investigate the stability, hydrolyzability, in vitro activity, and inhibition mechanism of bioactive peptides during the actual hydrolysis process. Six novel ACE-inhibitory peptides were screened from the Larimichthys crocea protein (LCP) and had low IC50 values (from 0.63 ± 0.09 µM to 10.26 ± 0.21 µM), which were close to the results of the QSAR model. After in vitro gastrointestinal simulated digestion activity of IPYADFK, FYEPFM and NWPWMK were found to remain almost unchanged, whereas LYDHLGK, INEMLDTK, and IHFGTTGK were affected by gastrointestinal digestion. Meanwhile, the inhibition kinetics and molecular docking results were consistent in that ACE-inhibitory peptides of different inhibition forms could effectively bind to the active or non-central active centers of ACE through hydrogen bonding. Our proposed method has better reproducibility, accuracy, and higher directivity than previous methods. This study can provide new approaches for the deep processing, identification, and preparation of Larimichthys crocea. [ABSTRACT FROM AUTHOR]

In this study, pancrelipase inhibitory peptides (PES) from an enzymatic protein hydrolysate of Chlorella pyrenoidosa were isolated and purified by ultrafiltration and Sephadex gel chromatography. The in vivo hypolipidemic activity of PES was evaluated by fat deposition and the levels of triglyceride (TG) and total cholesterol (TC) in Caenorhabditis elegans fed a high sugar diet. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify the peptide sequence of PES, and molecular docking was used to select potential pancreatic lipase inhibitory peptides, and the pancreatic lipase inhibitory activity of the synthesized peptides was verified. The results showed that PES had good hypolipidemic activity at a concentration of 1 mg/mL; it inhibited lipid deposition by 22.5%, and reduced the levels of TG and TC by 27.4% and 29.4%, respectively. In total, 999 peptides were identified, and four potential lipase inhibitory peptides were obtained. Among them, FLGPF had the best inhibitory effect on pancreatic lipase, with an inhibition rate of 50.12% at 8 mg/mL. The inhibition was reversible and non-competitive, with an inhibition constant of 5.23 mg/mL. Molecular docking showed that FLGPF could better bind to human pancreatic triacylglycerol lipase (PTL) via π-hydrogen, π-cation and hydrogen bond interactions. This study can provide a theoretical reference for the development and utilization of C. pyrenoidosa protein-derived hypolipidemic peptide.

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The inhibitory mechanism of α-amylase and α-glucosidase by cyanidin-3-O-glucoside was investigated by ultrafiltration, high performance liquid chromatography (HPLC), enzyme kinetics, and molecular docking. The results indicated that cyanidin-3-O-glucoside inhibited α-amylase and α-glucosidase in a reversible and non-competitive manner. Besides, the fluorescence quenching analysis indicated that cyanidin-3-O-glucoside combined with the two enzymes by hydrogen bonds to form a complex. Molecular docking analysis showed that cyanidin-3-O-glucoside interacted with the key amino acid residues of α-amylase and α-glucosidase through hydrogen bonds and hydrophobic forces, and the binding energies were −7.8 and −9.8 kcal/mol, respectively. Our research suggests that cyanidin-3-O-glucoside has the potential to be used as an inhibitor of α-amylase and α-glucosidase in the development of functional foods.

Food-derived angiotensin-I-converting enzyme (ACE)-inhibitory peptides have gained attention for their potent and safe treatment of hypertensive disorders. However, there are some limitations of conventional methods for preparing ACE-inhibitory peptides. In this study, in silico hydrolysis, the quantitative structure–activity relationship (QSAR) model, LC-MS/MS, inhibition kinetics, and molecular docking were used to investigate the stability, hydrolyzability, in vitro activity, and inhibition mechanism of bioactive peptides during the actual hydrolysis process. Six novel ACE-inhibitory peptides were screened from the Larimichthys crocea protein (LCP) and had low IC50 values (from 0.63 ± 0.09 µM to 10.26 ± 0.21 µM), which were close to the results of the QSAR model. After in vitro gastrointestinal simulated digestion activity of IPYADFK, FYEPFM and NWPWMK were found to remain almost unchanged, whereas LYDHLGK, INEMLDTK, and IHFGTTGK were affected by gastrointestinal digestion. Meanwhile, the inhibition kinetics and molecular docking results were consistent in that ACE-inhibitory peptides of different inhibition forms could effectively bind to the active or non-central active centers of ACE through hydrogen bonding. Our proposed method has better reproducibility, accuracy, and higher directivity than previous methods. This study can provide new approaches for the deep processing, identification, and preparation of Larimichthys crocea.

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A comprehensive method was applied to evaluate the anticoagulant activity of a novel anticoagulant peptide (NAESLRK) derived from oyster (Crassostrea gigas). The anticoagulant peptide drastically reduced the extrinsic clotting activity and also impaired the intrinsic clotting activity slightly. Consistent with clotting data, the thrombin peak height was reduced to 84.7 nmol/L from 123.4 nmol/L, and thrombin generation time was delayed to 4.67 min from 4.42 min when the extrinsic trigger was applied. The inhibitory kinetics of FXIa, FIXa, FXa, FIIa, and APC in a purified component system rationally explained the reduction of extrinsic clotting activity and impairment of thrombin generation. Besides the inhibition of FXa and FIIa activity, the activation processes of FX and FII by intrinsic/extrinsic tenase complex and prothrombinase were also damaged. The anticoagulant activity in the plasma system was the result of comprehensive inhibition of various factors. The research provided a novel method for anticoagulant evaluation and inhibitory mechanism of bioactive peptides from food products.

[Display omitted] • Migration substances from milk packaging (stearic acid and stearamide) can reduce the activity of proteases. • 500 μg/mL stearic acid and stearamide decreases the activity of gastric protease by 18 %. • The inhibitory effect of stearic acid and stearamide on gastric protease is non-competitive. • The binding of stearic acid and stearamide to proteases induces conformational changes in the enzyme. The effects of common migration substances in milk packaging on digestive protease were studied. We choose the common migrants found in eight types of multi-layer composite milk packaging. Enzyme activity experiments revealed that pepsin activity decreased by approximately 18 % at 500 μg/mL of stearic acid and stearamide treatment, while trypsin activity decreased by approximately 18 % only by stearic acid treatment (500 μg/mL). Subsequently, fluorescence spectroscopy, circular dichroism spectroscopy, and molecular docking technology were employed to investigate the inhibition mechanism of protease activity by migrating substances in three systems: stearic acid-trypsin, stearic acid-pepsin, and stearamide-pepsin. Results showed that the inhibitory effect of stearic acid on trypsin is a reversible mixed inhibition, whereas the inhibitory effects of stearic acid and stearamide on pepsin are non-competitive. In all three systems, ΔH < 0, ΔS < 0, and ΔG < 0, indicating the binding process between the migrant and the protease is a spontaneous exothermic process primarily driven by hydrogen bonding and van der Waals forces. In addition, their binding constants are all around 104 L/moL, indicating that there are moderate binding affinities exist between migrants and proteases. The binding process results in the quenching of the protease's endogenous fluorescence and induces alterations in the enzyme's secondary structure. Synchronized fluorescence spectroscopy showed that stearic acid enhanced the hydrophobicity near the Tyr residue of trypsin. The molecular docking results indicated that the binding affinity of stearic acid-trypsin, stearic acid-pepsin, and stearamide-pepsin was –22.51 kJ/mol, −12.35 kJ/mol, −19.28 kJ/mol respectively, which consistent with the trend in the enzyme activity results. This study can provide references for the selection of milk packaging materials and the use of processing additives, ensuring food health and safety. [ABSTRACT FROM AUTHOR]

The purpose of this study was to prepare a novel Angiotensin-I-Converting Enzyme(ACE) inhibitory peptide by hydrolyzing sheep casein with protease and analyze its molecular inhibitory mechanism, so as to provide technical support for the development of functional sheep milk polypeptide dairy products. In this experiment, sheep casein was used as raw material, with hydrolysis degree, ACE inhibition rate and molecular weight distribution as indexes, the most suitable protease was selected from four proteases, and the components with less than

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gut bacterial β-glucuronidase is regarded as an important molecular target for several therapeutic applications. Inhibitors of β-glucuronidase can effectively alleviate the drug-induced gastrointestinal tract toxicity. In this study, the ethanol extracts of black tea was found to display significant inhibitory activities against Escherichia coli β-glucuronidase (EcGUS), and seven polyphenols including catechins and theaflavins were identified as the key components responsible for the strong inhibitory potency of black tea towards EcGUS. Among these seven identified naturally occurring inhibitors, (−)-catechin gallate (CG), theaflavin-3-monogallate (TF-3-G), theaflavin-3′-monogallate (TF-3′-G) and theaflavin-3,3′-digallate (TFDG) were more potent inhibitors of EcGUS compared with (−)-epicatechin gallate (ECG), (−)-gallocatechin gallate (GCG), and (−)-epigallocatechin gallate (EGCG). Furthermore, molecular docking and molecular dynamics simulation results further indicated that TFDG could bind in the cavity of EcGUS and interacted with key residues Ser360, Glu413 and Ile560 of EcGUS through hydrogen bonds. Taken together, these data offer important information for efficient development of black tea and its catechins and theaflavins constituents for treating drug-induced enteropathy.

Quercetin is one of the most ubiquitous dietary flavonoids widely distributed in plants and foods of plant origin, and is a potent tyrosinase inhibitor. Quercetin fatty esters could lead to an improve in quercetin lipophilicity which could positively affect its pharmacological activity. In this study, the inhibitory effect of two novel esters of quercetin‐linoleic acid (ligand A) and quercetin‐oleic acid (ligand B) has been investigated on structure and diphenolase activity of mushroom tyrosinase (MT) by experimental and molecular docking techniques. The inhibitory kinetics study using UV‐visible spectrophotometry in the presence of its substrate 3,4‐dihydroxyphenylalanine (L‐dopa), revealed that both esters successfully inhibit the activity of tyrosinase and reduce the formation of dopaquinone. Results showed that the binding of ligands to MT induced rearrangement and conformational changes of the enzyme. Thermodynamic parameters of these interactions (Ka, ∆G°, ∆H° and ∆S°) were obtained at pH = 6.8 and temperatures of 298 and 310 K. Molecular docking studies further was applied to calculation of binding energies (ΔGbA = −21.84 kJ/mol, ΔGbB = −20.92 kJ/mol), inhibition constant values (KIA = 160 µM, KIB = 220 µM) and the special binding site. It can be deduced that ligands act as a potential tyrosinase inhibitor and it was found that the best possible interaction condition with binding modes visualize was achieved by ligand A and exhibited the potent tyrosinase inhibitory activity. These findings may be helpful to understand the inhibition mechanism of quercetin fatty acids esters on tyrosinase and provide a convenient screening method to differentiate phenolic tyrosinase inhibitors. Practical applications: Bioavailability and antioxidant activity of conjugated fatty acids with their bioequivalence in several biological effects and metabolic processes such as beta‐oxidation from various forms has been reported to be highly variable and useful. Quercetin shows beneficial role in human health, but its biological effects in vivo is limited by poor bioavailability, low skin permeability and solubility. This study design new tyrosinase inhibitors which helpful to functional research of unsaturated fatty acid esters in the treatment of inflammatory diseases and hyperpigmentation disorders. In addition, undesirable enzymatic browning of plant derived‐foods by tyrosinase causes a decrease in market value and economic loss of food products. The results suggest that the conjugation of quercetin with linoleic and oleic acids resulted in novel stronger tyrosinase inhibitors which may have therapeutic applications and replacement of toxic tyrosinase inhibitors and contribute as anti‐ browning agents in food, cosmetic and pharmaceutical industry. [ABSTRACT FROM AUTHOR]

Inhibition of α-glucosidase is considered as an effective approach to treat type 2 diabetes. Therefore, it is of great significance to study the inhibition of this enzyme. In the present study, the inhibitory activity of oleanolic acid (OA) on α-glucosidase and their interaction mechanism were investigated. The inhibition kinetic analysis showed that OA reversibly inhibited α-glucosidase activity in a mixed-type manner with an IC50 value of 3.04 ± 0.05 µM, and the inhibition followed a multi-phase kinetic process with a first-order reaction. The change of enthalpy and entropy indicated that the binding of OA to glucosidase was mainly driven by hydrophobic interaction and hydrogen bonding, and the binding distance was estimated at 3.51 nm. Synchronous fluorescence, circular dichroism (CD) and Fourier transform infrared spectra (FT-IR) showed that the binding of OA to α-glucosidase induced rearrangement and conformational changes of the enzymes. The molecular docking illustrated that OA entered the active center of α-glucosidase and interacted with the amino acid residues Asp-352 and ultimately inhibiting the enzyme activity. [ABSTRACT FROM AUTHOR]

Melanosis developed in shrimp (Penaeus vannamei) is mainly initiated by polyphenoloxidase (PPO), thus understanding of the characteristics of PPO in shrimp is important for controlling the melanosis of shrimp. The shrimp cephalothorax turns black most rapidly amongst all the tissues during the chilled storage. Crude PPO extracted from this cephalothorax has an optimal pH of 6.0 and an optimal temperature of 50 °C. PPO is relatively stable under neutral and weak alkaline conditions (pH 5.5–9.0) and the temperature range of 25–35 °C. The kinetic parameters Km and Vmax were recorded as 3.02 mM and 54.3 U/mg of protein, respectively, using L-Dopa as a substrate. The molecular weight of PPO was estimated as 200–220 kDa by an activity staining test. A hydroxypyridinone derivative, 5-hydroxy-1-octyl-4-oxo-1,4-dihydropyridine-2-carbaldehyde O-ethyl oxime, was demonstrated to efficiently inhibit the PPO, indicating that this compound might find application as a shrimp preservative. [ABSTRACT FROM AUTHOR]

An inhibitory uptake function is incorporated into the discrete, size-structured nonlinear chemostat model developed by Arino et al. (Journal of Mathematical Biology, 45(2002)). Different from the model with a monotonically increasing uptake function, we show that the inhibitory kinetics can induce very complex dynamics including stable equilibria, cycles and chaos (via the period-doubling cascade). In particular, when the nutrient concentration in the input feed to the chemostat S0 is larger than the upper break-even concentration value μ, the model exhibits three types of bistability allowing a stable equilibrium to coexist with another stable equilibrium, or a stable cycle or a chaotic attractor. [ABSTRACT FROM AUTHOR]

A chemical investigation of the roots of Euphorbia ebracteolata identified eighteen diterpenoids and glycosides. On the basis of spectroscopic data, they were determined to be ent -kauranes, ent -atisanes, tigliane derivatives, ingenane, and ent -abietanes, among which were eleven previously undescribed diterpenoids. The inhibitory effects of the isolated compounds against human carboxylesterase 2 (hCE-2) were evaluated in vitro , which revealed moderate inhibitory effects with IC 50 values < 50 μM. Next, the inhibitory kinetics were evaluated for the putative hCE-2 inhibitor 4 β ,9 α ,16,20-tetrahydroxy-14(13 → 12)-abeo-12 α H-1,6-tigliadiene-3,13-dione (IC 50 3.88 μM), and results indicated competitive inhibition with K i 4.94 μM. Additionally, none of the diterpenoids showed cytotoxic effects against five human tumor cell lines as determined by MTT assays. [ABSTRACT FROM AUTHOR]

52 Structure-based thiosemicarbazone compounds bearing various substituted-lipophilic part, including substituted-benzaldehyde, substituted-phenylalkan-1-one and their biphenyl-type thiosemicarbazone analogs, were designed, synthesized and evaluated as new tyrosinase inhibitors. The results demonstrated that 22 compounds have potent inhibitory activities against tyrosinase with the IC 50 value of lower than 1.0 μM. On the basis of the obtained experimental data, the structure-activity relationships (SARs) were rationally derived. Besides, the inhibition mechanism and the inhibitory kinetics of selected compounds 3d and 6e were investigated, revealing that such type of compounds were belonged to the reversible and competitive tyrosinase inhibitors. To verify the safety of these developed thiosemicarbazone compounds, four randomly selected compounds 3d , 4e , 6a and 9a were also tested in 293T cell line for the evaluation of the cytotoxicity. Interestingly, all these compounds almost did not perform any toxicity to 293T cells even at a high concentration of 1000 μmol/L. Taken together, these results suggested that such compounds could serve as the highly efficient and more safe candidates for the treatment of tyrosinase-related disorders. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) are widely used in commercial products because of their excellent antimicrobial activity. Entrance of AgNPs and its released Ag ions (Ag) into wastewater treatment plants could harm ammonia oxidation (AO) process resulting in environmental problems. This study investigated inhibitory kinetics and mechanism of AO from nitrifying sludge influenced by AgNPs and Ag. The findings demonstrated that AgNPs and Ag adversely influenced on AO. Silver ions were more toxic to AO than AgNPs, which was indicated by the lower inhibitory constant ( K ) of 0.29 mg/L compared to that of AgNPs ( K of 73.5 mg/L). Over the experimental period of 60 h, AgNPs at 1, 10, and 100 mg/L released Ag in the average concentrations of 0.059, 0.171, and 0.503 mg/L, respectively. Silver nanoparticles of 1-100 mg/L inhibited AO by 45-74%, whereas Ag of 0.05-0.50 mg/L inhibited AO by 53-94%. This suggested that the AgNP toxicity mainly derived from the liberated Ag. Scanning electron microscopy results revealed that AgNPs attached on microbial cell surfaces, and both AgNPs and Ag induced cell morphological change from rod shape to shorter rod shape. Transmission electron microscopy showed that AgNPs and Ag diminished the thickness of the outer layer and reduced the density of internal parts of the exposed microbial cells, which could be the reasons for the morphology change. Live/dead results also confirmed that AgNPs and Ag damaged membrane integrity of cells in the nitrifying sludge. This study suggested that the primary mechanism for toxicity of AgNPs was the liberation of Ag and then both of silver species caused cell death. [ABSTRACT FROM AUTHOR]

Tyrosinase is a key enzyme in post-harvest browning of fruit and vegetable. To control and inhibit its activity is the most effective method for delaying the browning and extend the shelf life. In this paper, the inhibitory kinetics of 4-hydroxy cinnamic acid on mushroom tyrosinase was investigated using the kinetics method of substrate reaction. The results showed that the inhibition of tyrosinase by 4-hydroxy cinnamic acid was a slow, reversible reaction with fractional remaining activity. The microscopic rate constants were determined for the reaction on 4-hydroxy cinnamic acid with tyrosinase. Furthermore, the molecular docking was used to simulate 4-hydroxy cinnamic acid dock with tyrosinase. The results showed that 4-hydroxy cinnamic acid interacted with the enzyme active site mainly through the hydroxy competed with the substrate hydroxy group. The cytotoxicity study of 4-hydroxy cinnamic acid indicated that it had no effects on the proliferation of normal liver cells. Moreover, the results of effects of 4-hydroxy cinnamic acid on the preservation of mushroom showed that it could delay the mushroom browning. These results provide a comprehensive underlying the inhibitory mechanisms of 4-hydroxy cinnamic acid and its delaying post-harvest browning, that is beneficial for the application of this compound. [ABSTRACT FROM AUTHOR]

α-Glucosidase is a therapeutic target for diabetes mellitus, and α-glucosidase inhibitors play a vital role in the treatments for the disease. As a kind of potentially safer α-glucosidase inhibitor, flavonoids have attached much attention currently. In this study, kaempferol was found to show a notable inhibition activity on α-glucosidase in a mixed-type manner with IC 50 value of (1.16 ± 0.04) × 10 −5 mol L −1 . Analyses of fluorescence, circular dichroism and Fourier transform infrared spectra indicated that kaempferol bound to α-glucosidase with high affinity which was mainly driven by hydrogen bonds and van der Waals forces, and this binding resulted in conformational alteration of α-glucosidase. Further molecular docking study validated the experimental results. It was proposed that kaempferol may interact with some amino acid residues located within the active site of α-glucosidase, occupying the catalytic center of the enzyme to avoid the entrance of p-nitrophenyl-α- d -glucopyranoside and ultimately inhibiting the enzyme activity. [ABSTRACT FROM AUTHOR]

• A simple method was developed for affinity screening of active component. • Schisandra chinensis possessed the potential lipase inhibitory activity. • 5-Hydroxymethyl-2-furaldehyde is a non-competitive inhibitor. • 5-Hydroxymethyl-2-furaldehyde interacted with lipase by van der Waals force, H-bonds. Schisandra chinensis (Turcz.) Baill has various biological activities including anti-obesity. Rapid analysis and screening of active compounds from natural extracts is one of the challenges faced by natural drug research. In order to analyze and screen lipase inhibitor from Schisandra chinensis extract, a method inspired by the specific binding of enzyme to ligand was developed and established. Through optimization of incubation conditions, such as time, temperature, and pH, the potential active compound was locked by comparing the change of the chemical components of the S. chinensis extract before and after incubation with lipase. Subsequently, the target compound was isolated by high-speed counter-current chromatography and was identified as 5-hydroxymethyl-2-furaldehyde. Moreover, in vitro activity determination confirmed that 5-hydroxymethyl-2-furaldehyde with an IC 50 value of 284.78 ± 16.45 μg/mL interacted with the lipase through non-competitive inhibition. Furthermore, molecular docking further revealed that 5-hydroxymethyl-2-furaldehyde can be embedded into the active pocket of lipase via multiple hydrogen bonds and other interactions. This study not only screened a potential lipase inhibitor from S. chinensis through the newly developed method, but also can be used as a typical reference for the discovery of active components from functional foods and natural products. [ABSTRACT FROM AUTHOR]

In this study, we developed 3-/4-aminoacetophenones and their structure-based 3-/4-aminophenylethylidenethiosemicarbazide derivatives, respectively, as novel tyrosinase activators and inhibitors. Notably, all the obtained thiosemicarbazones displayed more potent tyrosinase inhibitory activities than kojic acid. Especially, compound 7k was found to be the most active tyrosinase inhibitor with IC 50 value of 0.291 μM. The structure-activity relationships (SARs) analysis showed that: (1) the amine group was absolutely necessarily for determining the tyrosinase activation activity; (2) the introduction of thiosemicarbazide group played a very vital role in transforming tyrosinase activators into tyrosinase inhibitors; (3) the phenylethylenethiosemicarbazide moiety was crucial for determining the tyrosinase inhibitory activity; (4) the type of acyl group had no obvious effect on the inhibitory activity; (5) the position of amide substituent on the phenyl ring influenced the tyrosinase inhibitory potency. Moreover, the inhibition mechanism and inhibition kinetics study revealed that compound 7k was reversible and non-competitive inhibitor, and compound 8h was reversible and competitive-uncompetitive mixed-II type inhibitor. [ABSTRACT FROM AUTHOR]

In continuing our program aimed to search for potent compounds as highly efficient tyrosinase inhibitors, here a series of novel 4-alkoxy- and 4-acyloxy-phenylethylenethiosemicarbazone analogues were designed, synthesized and their biological activities on mushroom tyrosinase were evaluated. Notably, most of compounds displayed remarkable tyrosinase inhibitory activities with IC 50 value of lower than 1.0 μM. Furthermore, the structure–activity relationships (SARs) were discussed and the inhibition mechanism and the inhibitory kinetics of selected compounds 7k and 8d were also investigated. Taken together, these results suggested that such compounds could serve as the promising candidates for the treatment of tyrosinase-related disorders and further development of such compounds might be of great interest. [ABSTRACT FROM AUTHOR]

The cholesteryl ester transfer protein (CETP), inhibition of which assists in maintaining a high level of high-density lipoprotein cholesterol in the blood, is a target for anti-atherosclerosis treatments. Orange monascus pigment was produced by a Monascus species in a 5 L jar fermenter and various derivative compounds were synthesised by incorporating 19 different l-amino acids into the orange pigment. Among them, the l-Thr and l-Tyr derivatives exhibited high inhibitory activities against the CETP reaction. The inhibitory activities of the l-Thr and l-Tyr derivatives increased in a dose-dependent manner, resulting in IC50 values of 1.0 and 2.3 μM, respectively. When CETP reactions in the presence of the derivatives were performed, the inhibition modes of the l-Thr and l-Tyr derivatives were non-competitive with inhibition constant (Ki) values of 2.7 and 4.3 μM, respectively. [ABSTRACT FROM AUTHOR]

• Chlorogenic acid (CA) derivatives with different lipophilicities were synthesized. • CA derivatives extracts showed α-amylase and α-glucosidase inhibitory activities. • CA derivatives inhibited α-amylase/α-glucosidase by mixed mechanisms. • CA derivatives quenched intrinsic fluorescence by dynamic and static mechanism. • C12-CA exhibits stronger inhibitory activities compared with CA and acarbose. Due to the poor lipophilicity of chlorogenic acid (CA), five CA derivatives (C 2-CA, C4-CA, C6-CA, C8-CA, and C12-CA) with different lipophilicities were synthesized using acylation catalyzed by lipase in present study. The inhibitory activities and mechanisms of CA and its derivatives on α-amylase and α-glucosidase were then determined. Results showed that the inhibitory activities of CA derivatives on α-amylase and α-glucosidase were enhanced as lipophilicity increased, and the inhibitory activities of C12-CA were stronger than those of CA. IC 50 values of C12-CA were 13.30 ± 0.26 μmol/mL for α-amylase and 3.42 ± 0.10 μmol/mL for α-glucosidase. C12-CA possessed the smallest K ic and K iu values, and its inhibitory actions on α-amylase and α-glucosidase were stronger than those of CA and the other derivatives. Effects of C12-CA on microenvironments of amino acid residues and secondary structures of α-amylase and α-glucosidase were greater than those of CA and the other derivatives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Affinity-ultrafiltration strategy was used to figure α-glucosidase inhibitors. • 7 potential α-glucosidase inhibitors were identified from brown rice. • The type of inhibition of the inhibitors against α-glucosidase were measured. • The inhibitory mechanisms of 7 inhibitors were studied by molecular simulation. Brown rice bound phenolics extracts (BRBPE) have been reported to possess α-glucosidase inhibitory effects, the specific enzyme inhibitors involved in this process were unknown. Here, α-glucosidase inhibitors in BRBPE were screened using bioaffinity ultrafiltration methods, and seven phenolic compounds – three monomers (p -coumaric acid, ferulic acid and methyl ferulate), three dimers (8-5′, 5-5′ and 8- O -4′ diferulic acid) and a trimer (5-5′/8- O -4″ dehydrotriferulic acid) were identified as exact inhibitors, among which 5-5′/8- O -4″ dehydrotriferulic acid and 5-5′diferulic acid exhibited the best inhibitory activity. Enzyme kinetic analysis suggested that the inhibitory mechanism of these seven inhibitors including competitive, noncompetitive, uncompetitive and mixed manner. Molecular docking analysis revealed that the seven inhibitors bind with α-glucosidase mainly by hydrogen bonding interaction, hydrophobic force and ionic bond. Molecular dynamics simulation further explored the structure and molecular property of phenolic-glucosidase complex. This work provided a deep insight into brown rice bound phenolics acting as potent α-glucosidase inhibitors. [ABSTRACT FROM AUTHOR]

Abstract: The inhibitory kinetics of furfuryl alcohol, furfural and furoic acid on mushroom tyrosinase have been investigated. The results showed that these furan compounds were reversible inhibitors of the enzyme. Furthermore, furfuryl alcohol and furfural were found to be mixed-type inhibitors while furoic acid is uncompetitive inhibitor. The inhibition constants have been confirmed and the order of the inhibiting ability was furfural>furoic acid>furfuryl alcohol. They indicate that the functional groups on the furan ring play a crucial role in the inhibition on the enzyme. In addition, it was also found that these furan compounds could inhibit the proliferation of Salmonella bacteria and Bacillus subtilis to different extents. The minimum inhibitory concentration (MIC) values of furfuryl alcohol, furfural and furoic acid against B. subtilis and S. bacteria were 0.115, 0.027, 0.015 and 0.115, 0.029, 0.009μM, respectively. The minimum bactericidal concentration (MBC) values of that were 0.115, 0.027, 0.015 and 0.231, 0.121, 0.030μM, respectively. [Copyright &y& Elsevier]

Silver nanoparticles (AgNPs) have significantly increased in production and use for anti-microbial propose. This agent, after used, is released into sewerage system resulting in possibility to inactivate non-targeted microorganisms in wastewater treatment plants. In this study, the inhibitory effect of AgNPs on ammonia oxidation was investigated using respirometric assay. The initial concentrations of AgNPs and ammonia ranged 0.25-10.00 and 14-280 mg/L, respectively. Half saturation constant ( K) for ammonia oxidation was found to be 15.9 mg N/L. Under the presence of AgNPs, the maximum oxygen uptake rate and K declined. The effect of AgNPs was proved to follow an uncompetitive-like inhibition kinetic type with the inhibition coefficients ( K) of 5.5 mg/L. Increasing AgNPs from 0.25 to 10.00 mg/L inhibited 4 to 50 % of ammonia-oxidizing activities at the initial ammonia concentrations from 14 to 280 mg/L. Based on transmission electron microscopic observation, AgNPs could damage the microbial cells. All findings indicated that AgNPs substantially reduced ammonia-oxidizing microorganisms and their activities. Thus, special attention should be made to manage discharge of AgNPs into the environment. [ABSTRACT FROM AUTHOR]

Abstract: Three novel peptides, IQW, IRW and LKP, were predicted in our previous study in the thermolysin–pepsin ovotransferrin hydrolysate. The aims of the present study were to purify the peptides, and determine if the predicted peptides purified from the hydrolysate would have the same activity as the synthetic ones. We also determined the stability of the peptides under simulated gastrointestinal condition. IQW, IRW and LKP were then successfully purified from crude ovotransferrin hydrolysate through multi-step chromatographic purification comprising of cation exchange chromatography followed by three-step reverse-phase high performance liquid chromatography (RP-HPLC), and their sequences were analysed by UPLC-MS/MS. Our results showed that their activities were comparable to the synthetic ones. Simulated gastrointestinal incubation showed that IRW was degraded into a dipeptide of IR and a free amino acid of W by pancreatin, LKP was degraded into a dipeptide of KP and a free amino acid of L by mucosal peptidase, while IQW was stable against the digestive enzymes. [Copyright &y& Elsevier]

Gut bacterial β -glucuronidase is regarded as an important molecular target for several therapeutic applications. Inhibitors of β -glucuronidase can effectively alleviate the drug-induced gastrointestinal tract toxicity. In this study, the ethanol extracts of black tea was found to display significant inhibitory activities against Escherichia coli β -glucuronidase (EcGUS), and seven polyphenols including catechins and theaflavins were identified as the key components responsible for the strong inhibitory potency of black tea towards EcGUS. Among these seven identified naturally occurring inhibitors, (−)-catechin gallate (CG), theaflavin-3-monogallate (TF-3-G), theaflavin-3′-monogallate (TF-3′-G) and theaflavin-3,3′-digallate (TFDG) were more potent inhibitors of EcGUS compared with (−)-epicatechin gallate (ECG), (−)-gallocatechin gallate (GCG), and (−)-epigallocatechin gallate (EGCG). Furthermore, molecular docking and molecular dynamics simulation results further indicated that TFDG could bind in the cavity of EcGUS and interacted with key residues Ser360, Glu413 and Ile560 of EcGUS through hydrogen bonds. Taken together, these data offer important information for efficient development of black tea and its catechins and theaflavins constituents for treating drug-induced enteropathy. [ABSTRACT FROM AUTHOR]

Tarocystatin from Colocasia esculenta, a group-2 phytocystatin, is a defense protein against phytopathogenic nematodes and fungi. It is composed of a highly conserved N-terminal region, which is homological to group-1 cystatin, and a repetitive peptide at the C-terminus. The purified recombinant proteins of tarocystatin, such as full-length (FL), N-terminus (Nt) and C-terminus (Ct) peptides, were produced and their inhibitory activities against papain as well as their antifungal effects were investigated. Kinetic analysis revealed that FL peptide exhibited mixed type inhibition ( Kia = 0.098 μm and Kib = 0.252 μm) and Nt peptide showed competitive inhibition ( Ki = 0.057 μm), whereas Ct peptide possessed weak papain activation properties. A shift in the inhibitory pattern from competitive inhibition of Nt peptide alone to mixed type inhibition of FL peptide implied that the Ct peptide has an regulatory effect on the function of FL peptide. Based on the inhibitory kinetics of FL (group-2) and Nt (group-1) peptides on papain activity, an inhibitory mechanism of group-2 phytocystatins and a regulatory mechanism of extended Ct peptide have each been proposed. By contrast, the antifungal activity of Nt peptide appeared to be greater than that of FL peptide, and the Ct peptide showed no effect on antifungal activity, indicating that the antifungal effect is not related to proteinase inhibitory activity. The results are valid for most phytocystatins with respect to the inhibitory mechanism against cysteine proteinase. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two new C 32 tetracyclic triterpenoids characterized from Euonymus fortune. • Four compounds isolated from the genus Euonymus for the first time. • Wilforlide A displayed obvious inhibitory activities against α -glucosidase. α -Glucosidase plays an important role in catalyzing the hydrolytic cleavage of disaccharides into monosaccharides. In this study, a phytochemical investigation of the potential α -glucosidase inhibitory fraction from the aerial parts of Euonymus fortunei led to the isolation and identification of two new tetracyclic triterpenoids, fortunenones A and B (1 – 2), together with 11 known triterpenoids (3 – 13). Fortunenones A and B are rare C 32 triterpenoids possessing a 24,24-dimethyl group. The partial isolated compounds were evaluated their effects on α -glucosidase, of which echinochlorin D (5), lupenone (7), wilforlide B (12), and wilforlide A (13) exhibited remarkable inhibitory effects with the half inhibitory concentration ranged from 207.2 × 10−6 M to 388.3 × 10−6 M compared with the positive control, acarbose. An enzyme kinetics analysis by Lineweaver-Burk plots revealed that the inhibition types of the four active compounds were all mixed inhibition. Molecular docking further revealed that hydrophobic interactions and hydrogen bonds play an important role in the inhibition of α -glucosidase activity. Our results demonstrate the potential of E. fortunei extract and its constituents to inhibit α -glucosidase. [ABSTRACT FROM AUTHOR]

In order to study the transport of dicarboxylic acids through the contraluminal cell membrane of proximal tubular cells,H-methylsuccinate has been synthetized by catalytic hydration of methylfumarate. As the chromatography of radioactive material excreted in the urine after i.v. injection ofH-methylsuccinate shows, no metabolite is detectable during the first 3 min. After 10 min, less than 10% of the excreted radiolabel is metabolized. To measure the contraluminal influx ofH-methylsuccinate from the interstitium into cortical tubular cells, the renal vessels were clamped so that the proximal tubular lumina collapsed. Then Ringer solution was injected into the blood capillaries. It contained different concentrations ofH-methylsuccinate andC-inulin as extracellular space marker. After contact times between 1 and 10 s, this fluid was withdrawn from the capillaries and the disappearance ofH-methylsuccinate relative toC-inulin was measured. The morphological compartments in the outer cortex of the clamped glutaraldehyde-fixed kidney were evaluated by a stereological method. For proximal tubular cells a ratio of extracellular water space to intracellular space of 1:3.1 and a ratio extracellular water space to free cell water space of 1:2 was found. It was tested whether the experimental disappearance curves with 4 different starting concentrations ofH-methylsuccinate fit with the data from four model calculations. It was found that the data and the conditions of transport are consistent with the predictions of a facilitated diffusion model. In this model, a transport coefficient occurs which depends on the concentration ofH-methylsuccinate following saturation kinetics. The calculated parameters wer: K forH-methylsuccinate=0.12 mmol/l, J=0.50 pmol/s ·cm (related to tubular length in cm). Furthermore, equations are given to calculate inhibitory constants K of competing dicarboxylic acids. [ABSTRACT FROM AUTHOR]

Quercetin is one of the most ubiquitous dietary flavonoids widely distributed in plants and foods of plant origin, and is a potent tyrosinase inhibitor. Quercetin fatty esters could lead to an improve in quercetin lipophilicity which could positively affect its pharmacological activity. In this study, the inhibitory effect of two novel esters of quercetin-linoleic acid (ligand A) and quercetin-oleic acid (ligand B) has been investigated on structure and diphenolase activity of mushroom tyrosinase (MT) by experimental and molecular docking techniques. The inhibitory kinetics study using UV-visible spectrophotometry in the presence of its substrate 3,4-dihydroxyphenylalanine (L-dopa), revealed that both esters successfully inhibit the activity of tyrosinase and reduce the formation of dopaquinone. Results showed that the binding of ligands to MT induced rearrangement and conformational changes of the enzyme. Thermodynamic parameters of these interactions (K a , ∆G°, ∆H° and ∆S°) were obtained at pH = 6.8 and temperatures of 298 and 310 K. Molecular docking studies further was applied to calculation of binding energies (ΔG bA  = -21.84 kJ/mol, ΔG bB  = -20.92 kJ/mol), inhibition constant values (K IA  = 160 µM, K IB  = 220 µM) and the special binding site. It can be deduced that ligands act as a potential tyrosinase inhibitor and it was found that the best possible interaction condition with binding modes visualize was achieved by ligand A and exhibited the potent tyrosinase inhibitory activity. These findings may be helpful to understand the inhibition mechanism of quercetin fatty acids esters on tyrosinase and provide a convenient screening method to differentiate phenolic tyrosinase inhibitors. PRACTICAL APPLICATIONS: Bioavailability and antioxidant activity of conjugated fatty acids with their bioequivalence in several biological effects and metabolic processes such as beta-oxidation from various forms has been reported to be highly variable and useful. Quercetin shows beneficial role in human health, but its biological effects in vivo is limited by poor bioavailability, low skin permeability and solubility. This study design new tyrosinase inhibitors which helpful to functional research of unsaturated fatty acid esters in the treatment of inflammatory diseases and hyperpigmentation disorders. In addition, undesirable enzymatic browning of plant derived-foods by tyrosinase causes a decrease in market value and economic loss of food products. The results suggest that the conjugation of quercetin with linoleic and oleic acids resulted in novel stronger tyrosinase inhibitors which may have therapeutic applications and replacement of toxic tyrosinase inhibitors and contribute as anti- browning agents in food, cosmetic and pharmaceutical industry., (© 2021 Wiley Periodicals LLC.)