Blood glucose-lowering activity of protocatechuic acid is mediated by inhibiting a-glucosidase

α-Glucosidase inhibitors are effective in controlling postprandial hyperglycemia,which play crucial roles in the management of type 2 diabetes.Protocatechuic acid(PCA)is one of phenolic acids existing not only in various plant foods but also as a major microbial metabolite of dietary anthocyanins in the large colon.The present study investigated the inhibitory mechanism of PCA on a-glucosidase in vitro and examined its effect on postprandial blood glucose levels in vivo.Results from in vitro experiments demonstrated that PCA was a mix-type inhibitor of a-glucosidase.Driven by hydrogen bonds and van der Waals interactions,PCA reversibly bound withα-glucosidase to form a stable a-glucosidase-PCA complex in a spontaneous manner.The computational simulation found that PCA could insert into the active cavity of a-glucosidase and establish hydrogen bonds with catalytic amino acid residues.PCA binding aroused the steric hindrance for substrates to enter active sites and caused the structural changes of interacted catalytic amino acid residues.PCA also exhibited postprandial hypoglycemic capacity in diabetic mice.This study may provide the theoretical basis for the application of PCA as an active ingredient of functional foods in dietary management of diabetes.

Insights into the mechanism of Sub3 inhibiting Fusarium moniliforme infection in maize

Fusarium moniliforme(F.moniliforme) and its secondary metabolite fumonisin pose a severe threat to food safety,and searching for effective antimicrobial agents is a focus of current research.In this study,the secondary structure of Sub3 was analyzed by circular dichroism,meanwhile,the inhibition rate of Sub3 against spores,mycelia of F.moniliforme and infected maize was studied.To explore the possible inhibition mechanisms,morphological and structural changes of spores treated with Sub3 at0,1/2 MIC(minimum inhibitory concentration) and MIC were observed by scanning electron microscopy and transmission electron microscopy;the cell wall integrity,membrane integrity,reactive oxygen species,mitochondrial membrane potential,ATP synthase activity,redox reactions,and the nuclear damage of F.moniliforme were also investigated.The results showed that Sub3 was mostly in the state of random in deionized water,while mainly showed the β-sheet structure in the hydrophobic environment of 50% Trifluoroethanol(TFE) solution,indicating that Sub3 might generate partial structure deformation when acting on the cell membrane;and its MIC on F.moniliforme spores was 0.2 g/L.Under the 1/2 MIC and MIC,the inhibition rates of Sub3 against F.moniliforme infected maize were 34.3% and75.6%,respectively.The results of inhibition mechanisms revealed that the defective pathogenicity of F.moniliforme caused by Sub3 was attributed to damages on both the cell wall and the cell membrane,which might upset balance of intracellular redox system and mitochondrial energy metabolism and trigger nucleus damage,ultimately leading to cell death.Meanwhile,Sub3 could diminished ATP synthase enzyme activity in a dose-dependent manner.The results provided direct evidence for inhibition of F.moniliforme infection of maize by Sub3,and useful knowledge applicable for food preservation.

Corrosion Inhibition Mechanism of Rare Earth Metal on LC4 Al Alloy with Spilt Cell Technique

A new method of studying the corrosion inhibition mechanism of rare earth metal（REM） on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl3, the influence of corrosive performance of CeCl3 on LC4 super-power aluminum ＂alloy in the 0.1 mol· L^-1 NaCl solution was investigated. Meanwhile, the conditional changes of pH values, CeCl3 solution, additire and time of performance were also studied. Finally, the features of electrode surface were revealed by using SEM and X-ray energy-dispersive spectrometry （EDS）. By combining these with other electric chemical techniques, such as potential-time curve, polarization curve et al.

Mechanism study of organic antioxidant and inorganic salt on suppressing coal oxidation

The advantages and disadvantages of organic antioxidant and inorganic salt on suppressing coal oxidation were analyzed on the basis of the theory that coal oxidation mechanisms can be attributed to the free radical chain-type reaction mechanism. The inhibition curves on suppressing coal oxidation of the different type and different concentration of organic antioxidant and inorganic salt were given through experimental study and data processing. Then some conclusions can be gained from the experimental study combining with theoretical analysis. First the inhibition mechanism of the organic antioxidant and inorganic salt is different. The former is that the chemical action is the dominant position. It can be called as the chain termination theory because the free radical is captured during coal oxidation. And the later is that the physical effect is the dominant position. It can be called as the decreasing-temperature theory because the liquid membrane which was formed by the inorganic salt can make coal body be the state of wetness and prevent oxygen from coal surface. Second the inhibition effect of the organic antioxidant is higher than the inorganic salt in the later period. But it is lower in the early period.

Trans-cinnamaldehyde inhibits Penicillium italicum by damaging mitochondria and inducing apoptosis mechanisms

Plant-derived essential oils have excellent antifungal effects and can be used for the preservation of fresh foods such as fruits and vegetables, but the detailed mechanism has not been fully elucidated. In this study, we investigated the inhibitory effects of trans-cinnamaldehyde on Penicillium italicum, a common pollution fungus in citrus, and explored the antifungal mechanism of trans-cinnamaldehyde by detecting fungal oxidative damage, mitochondrial metabolism, and cell apoptosis. These results showed that transcinnamaldehyde made the carboxylic acid cycle deregulated by altering the related enzyme activities(succinate dehydrogenase, malate dehydrogenase) and mid product. Moreover, the level of reactive oxygen species rose sharply while the redox level was out of regulation. The mitochondrial membrane potential collapsed, leading to the leakage of cytochrome c, and then triggering the activation of apoptotic protease, which was further confirmed by the significant increase in caspase-3 activity from(3.6 ± 0.6) U to(8.8 ± 1.1) U(P < 0.05). The cytochrome c in mitochondria was detected by confocal Raman microspectroscopy, the characteristic intensity index(I750/I2944) was decreased, indicating that the cytochrome c in mitochondria was reduced and leakage. Besides, the strong negative correlation between Raman intensity and the amount of cytochrome c leakage was established with the correlation coefficient of-0.981 7. This study revealed that destroying the integrity of the mitochondrial membrane, activating the mitochondrial-mediated apoptosis pathway was the in-depth antifungal mechanism of trans-cinnamaldehyde;and Raman spectroscopy technology provided new ideas to study this process with high sensitivity determination of cytochrome c.

Inhibition Mechanism of Cholinesterases by Carbamate: A Theoretical Study

The density functional theory at the B3LYP/6-311G（d, p） level was applied to exploring the inhibition mechanism of cholinesterases by carbamate. The results indicate that the inhibition reactions with or without the catalytic effect of the catalytic triad in eholinesterases underwent a two-step addition-elimination mechanism, which is in good agreement with the proposed mechanism. The solvent has a strong effect on the inhibition reactions and the reaction with the catalytic triad in the solvent phase is close to the real reaction under biological condition.

Inhibition Mechanism of Antifungal Monomer DZP8 against Rhizoctonia solani

In order to study the inhibition mechanism of antifungal monomers DZP8 produced by streptomyces 702 strain against Rhizoctonia solani, the effects of DZP8 on mycelial morphology were investigated under light microscope, and the effects of DZP8 on mycelial inclusion leakage and cell membrane damage of myceli-um were determined. The results showed that DZP8 caused a series of changes in mycelial morphology of R. solani in liquid culture condition. DZP8 treatments with concentrations of 1.81 and 3.35 μg/mL for 24 h caused big vacuole, rough surface and more inclusions of mycelium. With the treatment time prolonging, the mycelium distorted and appeared irregular constriction. DZP8 treatment with concentration of 20.10 μg/mL led to the increase of conductivity of mycelium culture liquid, leakage of soluble sugar and protein, and the lipid peroxidation of mycelium membrane. It was found that DZP8 at a very low concentration could cause changes of mycelial morphology of R. solani, while only a certain concentration could cause significant damage to cell membrane. This indicated that cell membrane might be one of the action sites of DZP8, and it might have other action sites or mechanism.

High-temperature corrosion of phosphate completion fluid and corrosion inhibition method by membrane transformation

By analyzing the corrosion of phosphate completion fluid on the P110 steel at 170 °C, the high-temperature corrosion mechanism of phosphate completion fluid was revealed, and a corrosion inhibition method by membrane transformation was proposed and an efficient membrane-forming agent was selected. Scanning electron microscope (SEM) images, X-ray energy spectrum and X-ray diffraction results were used to characterize the microscopic morphology, elemental composition and phase composition of the precipitation membrane on the surface of the test piece. The effect and mechanism of corrosion inhibition by membrane transformation were clarified. The phosphate completion fluid eroded the test piece by high-temperature water vapor and its hydrolyzed products to form a membrane of iron phosphate corrosion product. By changing the corrosion reaction path, the Zn2+ membrane-forming agent could generate KZnPO4 precipitation membrane with high temperature resistance, uniform thickness and tight crystal packing on the surface of the test piece, which could inhibit the corrosion of the test piece, with efficiency up to 69.63%. The Cu2+ membrane-forming agent electrochemically reacted with Fe to precipitate trace elemental Cu on the surface of the test piece, thus forming a protective membrane, which could inhibit metal corrosion, with efficiency up to 96.64%, but the wear resistance was poor. After combining 0.05% Cu2+ and 0.25% Zn2+, a composite protective membrane of KZnPO4 crystal and elemental Cu was formed on the surface of the test piece. The corrosion inhibition efficiency reached 93.03%, which ensured the high corrosion inhibition efficiency and generated a precipitation membrane resistant to temperature and wear.

Research Advances in the Inhibition of Long Chain Fatty Acid to Methanogenic Activity in Anaeroic Digestion System

This article reviewed the inhibition mechanism of long chain fatty acid on the formation of anaerobic system, then thoroughly analyzed the inhibition factors of long chain fatty acid, and summarized the remission method to its inhibition, finally proposed some suggestions to further study on the influence of long chain fatty acid on anaerobic digestion system.

Co-inhibition of methanogens for methane mitigation in biodegradable wastes

The inhibition effects and mechanisms of chlorinated methane and acetylene on methanogenesis in the anaerobic digestion process of the biodegradable wastes were investigated.It was found that both chloroform and acetylene could effectively inhibit methanogens while the biodegradability of the wastes was not affected.Acetylene inhibited the activity of methanogens,while chloroform inhibited metabolic process of methanogenesis.A central composite design（CCD） and response surface regression analysis（RSREG） were employed to determine the optimum conditions and interaction effects of chloroform and acetylene in terms of inhibition effciency,production of volatile fatty acids（VAF） and molar ratio of propionic acid to acetic acid.Chloroform had significant effect on enhancing the production of VFA（F = 121.3;p 〈 0.01）,and acetylene promoted the inhibition effciency（F = 99.15;p 〈 0.05） more effectively than chloroform（F = 9.72;p 〉 0.05）.In addition,a maximum molar ratio of propionic acid to acetic acid of 1.208 was estimated under the optimum conditions of chloroform concentration of 9.05 mg/kg and acetylene concentration of 3.6×10^-3（V/V）.Hence,methanogens in the wastes can be inhibited while the stabilization process of the biodegradable wastes can still work well,as propionic acid generated during the inhibition process could hardly be utilized by methanogens.

Studies on Complexation of ATMP, PBTCA, PAA and PMAAA with Ca^(2+) in Aqueous Solutions

By means of acid-base potentiometric titration and the advanced BEST computer program developed by Martell et al., the deprotonation constants of four inhibitors[Aminotrimethylenephosphoinic acid(ATMP), 2-phosphino-tutane-1,2,4-tricarboxylic acid(PBTCA), polyacrylic acid(PAA, M_w=2000), poly(maleic, acrylic) acid(PMAAA, M_w=3000)], and the stability constants of the complexes of these inhibitors with Ca 2+ have been determined. And the distribution curves of ATMP at different pH values in aqueous solutions have also been given out. The result of this study can be applied to explaining the inhibition mechanism.

Notoginsenoside as an environmentally friendly shale inhibitor in water-based drilling fluid

The demand for non-toxic and biodegradable shale inhibitors is growing in the drilling industry.In this paper,the effect of notoginsenoside(NS)as a new,environmentally friendly inhibitor of shale hydration is systematically studied for the first time.The inhibition performance of NS was evaluated via inhibition evaluation tests,including mud ball immersion tests,linear expansion tests,shale rolling recovery tests,and compressive strength tests.The inhibition mechanism of NS was analyzed using Fourier transform infrared spectroscopy(FTIR),contact angle measurements,particle size distribution determination,thermogravimetric analysis(TGA),and scanning electron microscopy(SEM).The experimental results demonstrate that NS is able to adhere to the clay surface,forming a hydrophobic film that prevents the entry of water molecules and inhibiting the hydration dispersion of the clay.Because of this,NS can maintain the original state of bentonite pellets in water,which can effectively reduce the swelling rate of bentonite,increase the recovery rate of shale drill cuttings,maintain the strength of the shale,and therefore maintain the stability of the borehole wall during drilling.In addition,NS is non-toxic,degradable,and compatible with water-based drilling fluids.The above advantages make NS a promising candidate for use as an environmentally friendly shale inhibitor.

Surface lurking and interfacial ion release strategy for fabricating a superhydrophobic coating with scaling inhibition

The design and manufacture of anti-scaling surface is a prospective way to prevent scaling in oil field.In this work,a novel superhydrophobic Cu^(2+)-loaded and DTPMPA-modified anodized copper oxide(S-Cu^(2+)/D-ACO)coating was fabricated by modification of 1H,1H,2H,2H-perfluorodecyltriethoxysilane.The valid storing of scale inhibitors at the coating surface and the interfacial release of Cu^(2+)ions contribute to enhancing the anti-scaling of the S-Cu^(2+)/D-ACO coating.The water contact angle of the S-Cu^(2+)/D-ACO coating is 163.03°and exhibits superhydrophobicity,which makes it difficult for CaCO_(3)to deposit at the surface of the coating.DTPMPA will steadily lurk into the inner space,and Cu^(2+)will be loaded at the interface in the form of the DTPMPA:Cu^(2+)chelate.During the deposition of CaCO_(3),the dynamic release of DTPMPA can be realized by transferring DTPMPA:Cu^(2+)to DTPMPA:Ca^(2+).Interestingly,the released Cu^(2+)hinders the active growth of CaCO_(3).After 48 h of scaling,the mass of CaCO_(3)scale at the S-Cu^(2+)/D-ACO coating surface is only 44.1%that of the anodized copper oxide coating.The excellent anti-scaling performance of the S-Cu^(2+)/D-ACO coating is determined by the synergistic effect of the DTPMPA lurking and dynamic release,as well as the Cu^(2+)inhibition at the interface of superhydrophobic coating and against CaCO_(3)deposition.This research provides a new exploration for designing and fabricating anti-scaling superhydrophobic surface for oil field development.

Passivation of corrosion product layer on AM50 Mg by corrosion inhibitor

The influence of sodium dodecyl sulfate(SDS)on morphology and chemical composition of corrosion product layer formed onα-Mg matrix and cathodic Al-Mn intermetallic was systematically investigated by using FIB and TEM analysis for the first time to disclose the underlying inhibition mechanism.A porous corrosion bi-layer composed of crystalline MgO and Mg(OH)_(2)was observed on both ofα-Mg and Al-Mn intermetallic.It was found that a passive inner layer was deposited onα-Mg after immersion in SDS-containing NaCl solution,which can be ascribed to steady-state growth of magnesium and aluminum oxide under the protection of hydrophobic group of SDS.The inhibition mechanism of the inhibitor was mainly associated with formation of dense oxide layer onα-Mg matrix and preferential adsorption of SDS on the corrosion layer deposited on Al-Mn intermetallic.

Co-adsorption of O_2 and H_2O on α-uranium(110) surface:A density functional theory study

First-principles calculations based on density functional theory corrected by Hubbard parameter U （DFT＋U） are applied to the study on the co-adsorption of O2 and H2O molecules to a-U（110） surface. The calculation results show that DFT＋U method with Ueff = 1.5 eV can yield the experimental results of lattice constant and elastic modulus of a-uranium bulk well. Of all 7 low index surfaces of a-uranium, the （001） surface is the most stable with lowest surface energy while the （110） surface possesses the strongest activity with the highest surface energy. The adsorptions of O2 and H2O molecules are investigated separated. The O2 dissociates spontaneously in all initial configurations. For the adsorption of H2O molecule, both molecular and dissociative adsorptionsoccur. Through calculations of co-adsorption, it can be confirmed that the inhibition effect of O2 on the corrosion of uranium by water vapor originates from the preferential adsorption mechanism, while the consumption of H atoms by O atoms exerted little influence on the corrosion of uranium.

Identifi cation and characterization of a novel tetrapeptide from enzymatic hydrolysates of Baijiu byproduct

In order to prepare angiotensin I-converting enzyme(ACE)inhibitory peptides,distilled spent grains of Chinese strong-flavor Baijiu were hydrolyzed by alcalase followed by papain under optimized conditions.A superior ACE inhibitory peptide was separated and purifi ed by ultrafi ltration and high-performance liquid chromatography(HPLC),and its amino acid sequence was further identified as Gln-Gly-Val-Pro(QGVP)by electrospray mass spectrometry(ESI-MS).QGVP formed 6 hydrogen bonds with the active site of ACE,which is responsible for reducingα-helix structure content of ACE causing subsequent inactivation.M oreover,it showed no significant cytotoxicity toward human umbilical vein endothelial cells(HUVECs),a nd signifi cantly i nduced phosphorylation of endothelial nitric oxide synthase(p-e NOS)and decreased endothelin 1(END1)expression in angiotensin I(Ang I)-treated HUVECs,demonstrating the potential antihypertensive effect.The peptide QGVP hydrolyzed from distilled spent grain proteins of Chinese strong-fl avor Baijiu was expected to be used as a food ingredient to prevent or co-treat hypertension with other chemical drugs.

Grape Skin Polyphenols （GSPs） Inhibit the Migration of Mouse Mammary Carcinoma 4T1 Cells in Vitro

OBJECTIVE 1） To study the efficacy of GSPs on the migration of highly metastatic mammary carcinoma cells and 2） To investigate inhibition mechanisms.METHODS Cell migration was assessed using a 24-well transwell assay. Cells with different concentrations of GSPs were suspended （5×105 cell/mL） in RPMI 1640 media in the upper chamber, and RPMI 1640 media with 10% FBS was supplemented in the lower chamber. Then, cells were allowed to migrate for 24 h.RESULTS GSPs inhibited the migration of 4T1 cells in a dosedependent manner. The migration of 4T1 cells was obviously inhibited by GSPs, even at a very low concentration （5 μg/mL）,and was totally inhibited when the concentration was 20 μg/mL.Also, 20 μg/mL of GSPs inhibited cell viability by only 11.4% and induced early apoptosis by only 5.6% compared with a percentage of 4.0% in control cells. GSPs suppressed the activation of PDK1,Akt and Erk1/2 in a dose-dependent manner.CONCLUSION GSPs significantly inhibit the migration of highly metastatic mammary carcinoma 4T1 cells in vitro. This inhibition is independent of decreased cell viability or apoptosis induction. The inhibition of migration by GSPs is involved in blocking the PI3k/Akt and MAPK pathways.

Spontaneous escape behavior of silver from graphite-like carbon coating and its inhibition mechanism

A series of silver-doped graphite-like carbon coatings was prepared on the surface of aluminum alloy using the magnetron sputtering method. The spontaneous escape behavior and inhibition mechanism of silver from graphite-like carbon coating were studied. The results showed that when the sample prepared with a 0.01-A current on the silver target was placed in an atmospheric environment for 0.5 h, an apparent silver escape phenomenon could be observed. However, the silver escape phenomenon was not observed for samples prepared with a 0.05-A current on the silver target if the sample was retained in a 10^（-1） Pa vacuum environment, even after 48 h. Compared with the sample placed in the atmospheric environment immediately after an ion plating process, the silver escape time lagged for 6 h. Nanometer-thick pure carbon coating coverage could effectively suppress silver escape. When the coating thickness reached700 nm, permanent retention of silver could be achieved in the silver-doped graphite-like carbon coating.As the silver residue content in the graphite-like carbon coating increased from 2.27 at.% to 5.35 at.%, the interfacial contact resistance of the coating decreased from 51mΩcm^2 to 6 mΩcm^2.

The inhibition mechanisms of pancreatic lipase by apigenin and its anti-obesity mechanisms revealed by using network pharmacology

This study aimed to elucidate the inhibition mechanism of apigenin against porcine pancreatic lipase(PPL),and,moreover,to comprehensively reveal the molecular basis of its anti-obesity via network pharmacology approach.The results showed that apigenin inhibited PPL with an IC50 value of 0.377±0.041 mM.Spectroscopic techniques combined molecular docking suggested that apigenin could bind into the PPL active pocket,affecting its normal spatial conformation.Moreover,molecular dynamic(MD)simulations revealed that the open conformation of PPL tended to transit to the closed in the presence of apigenin,which might one important reason for the inhibition of PPL catalytic ability.Network pharmacology analysis revealed that a total of 49 proteins could be identified as potential targets for the anti-obesity effects of apigenin.According to the protein-protein interaction(PPI)network analysis,six hub targets were extracted including IGF1,ESR1,MMP9,PPARA,MAPK14 and NR3C1.Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway enrichment indicated that the 49 potential targets could be mapped to 30 pathways(p<0.05).Among them,PI3K-Akt signaling pathway and insulin resistance can be considered as two major pathways regulated by apigenin.Further docking studies indicated that apigenin can bind into the binding pocket of the six hub target proteins identified according to the PPI network.The results indicated that in addition to inhibiting PPL,apigenin could exhibit anti-obesity benefit through the molecular mechanisms uncovered by network pharmacology.This study proposes a new strategy to reveal the mechanisms of dietary polyphenols at the level of network pharmacology.