Mixed Inhibitor Research Articles

The effect of mixed tobacco monoamine oxidase inhibitors in animal models relevant to tobacco dependence

The effect of mixed tobacco monoamine oxidase inhibitors in animal models relevant to tobacco dependence

Corrosion inhibition performance of expired amlodipine on cupronickel alloy in a neutral chloride environment: electrochemical and surface analysis

Purpose The corrosion of cupronickel and copper alloys in marine and chloride environments presents significant challenges in the chemical and petrochemical industries. This paper aims to investigate the corrosion inhibition of cupronickel alloy (Cu-10Ni) in a sodium chloride medium using expired amlodipine as a corrosion inhibitor. The use of this drug in its expired form could reduce the costs of corrosion and help mitigate the accumulation of pharmaceutical waste. Design/methodology/approach The inhibitory action was evaluated using a weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effect of temperature on the inhibition performance was also studied. Findings The results of these experiments demonstrated that the drug amlodipine effectively inhibited the corrosion of cupronickel alloy in chloride solutions. The corrosion rate of cupronickel was found to decrease with increasing inhibitor concentration and to increase with rising temperature. A maximum inhibition efficiency of 91.92 was achieved with an inhibitor concentration of 0.025 g/L at 298 K. Adsorption of the inhibitor followed the Langmuir adsorption isotherm. Polarization studies indicated that the expired drug acted as a mixed inhibitor. SEM and AFM analyses confirmed that the surface morphology of cupronickel specimens was significantly improved in the presence of the inhibitor. Practical implications Amlodipine can be conveniently used to mitigate problems with the corrosion of copper alloys in chloride environments. Originality/value Amlodipine is evaluated as a novel and effective corrosion inhibitor for cupronickel alloy in neutral chloride environments.

Discovery of Chalcone Derivatives as Bifunctional Molecules with Anti-SARS-CoV-2 and Anti-inflammatory Activities.

Danshensu extracted with traditional Chinese medicine Salvia miltiorrhiza has a wide range of bioactivities. Danshensu containing a catechol moiety has a moderate inhibitory effect on SARS-CoV-2 3CLpro (IC50 = 2.2 μM) by a reversible covalent interaction and exhibits good anti-inflammatory activity. To enhance the inhibitory activity, we introduced Michael receptors into the side chain of danshensu as a possible covalent warhead and blocked the covalent binding sites of catechol moiety to yield chalcone derivatives. The resulting chalcone derivatives, A4 and A7, were found to inhibit SARS-CoV-2 3CLpro in vitro with IC50 values of 83.2 and 261.3 nM, respectively. Furthermore, A4 and A7 inhibit viral replication in the SARS-CoV-2 replicon system with EC50 values of 19.9 and 11.7 μM, respectively. Time-dependent inhibition experiment and mass spectrometry show that A4 acted as a noncovalent mixed inhibitor, while A7 likely binds covalently at Cys145. The interaction mechanism between SARS-CoV-2 3CLpro and A4 or A7 was characterized by molecular docking studies. Additionally, both A4 and A7 demonstrated potent anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. These promising results suggest that chalcone derivatives A4 and A7 can serve as bifunctional molecules with both antivirus and anti-inflammatory properties.

Effect of plant extract additives on the parasitic reaction in alkaline Zn-air batteries

The battery's high energy density, economical price, and ecological sustainability of the Zn-air battery make it a bright future battery technology. However, parasitic reactions, which can diminish the battery's life cycle and efficacy, are the key challenges for potential development of Zn-air batteries. Glycyrrhiza glabra roots extract (GGRE) has been investigated as an alternative hydrogen gas evolution and corrosion inhibitor for Zn-air batteries in order to mitigate the parasitic reaction. The results obtained reveal that the inhibition capacity of the GGRE extract increases with concentration and reaches its highest level (75.6%) around 350 mg L-1 of GGRE extract. GGRE extract is a mixed type inhibitor with a predominately cathodic effect based on the polarization data. The GGRE extract adsorption on the Zn surface complies with Freundlich isotherm. In comparison to the blank Zn-KOH (354 mAh g-1), the battery containing 350 mg L-1 GGRE extract has the highest discharge capacity (533 mAh g-1) and the best cyclability (92.9% retention after 500 cycles). Overall, GGRE extract can significantly optimize the performance of Zn-air batteries.

Potential skincare benefits and self-healing properties of Lignosus rhinocerotis polysaccharides as affected by ultrasound-assisted H2O2/Vc treatment

Natural polysaccharides have been recognized as major bioactive components in skincare and wound care products. In this study, the skincare benefits and self-healing properties of Lignosus rhinocerotis polysaccharides (LRP) and its degraded products (DLRP-1, DLRP-2 and DLRP-3) by ultrasound assisted H2O2/Vc treatment (U-H/V) at different ultrasonic intensity (28.14, 70.35, and 112.56 W/cm2) were investigated. U-H/V altered the internal crystalline structure and microstructure of LRP, and enhanced the thermal stability. Due to the breakage of molecular chains after U-H/V, the moisture absorption of LRP was enhanced but the moisturizing property showed a different degree of reduction. U-H/V significantly improved the antioxidant, anti-tyrosinase and anti-inflammatory activities of LRP. Furthermore, the results of enzyme kinetic studies showed a mixed competitive-noncompetitive inhibition of tyrosinase activity by DLRP-3 and the inhibition constant of DLRP-3 on tyrosinase was 2.97 mg/mL. The apparent viscosity of LRP dispersions showed a first increasing followed by decreasing trend as ultrasonic intensity rose. U-H/V enhanced the viscoelastic properties of LRP gels without destroying their self-healing properties. This findings reveal that U-H/V is beneficial for improving the skincare efficacy of LRP, providing a theoretical foundation for the applicability of LRP in wound dressings.

Study on the effects of endogenous polyphenols on the structure, physicochemical properties and in vitro digestive characteristics of Euryales Semen starch based on multi-spectroscopies, enzyme kinetics, molecular docking and molecular dynamics simulation

Euryales Semen (ES) is a highly nutritious food with low digestibility, which is closely associated with its endogenous phenolic compounds. In this study, five phenolic compounds (naringenin, isoquercitrin, gallic acid, epicatechin and quercetin) with high concentrations in ES were selected to prepare starch-polyphenol complexes. Subsequently, the effects of endogenous polyphenols on the structure, physicochemical properties and digestion characteristics of ES starch were studied using multiple techniques. The addition of phenolic compounds markedly reduced the in vitro digestibility, swelling power, gelatinization enthalpy, while increased the solubility of ES starch. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that phenolic compounds interacted with the starch through non-covalent bonds. Five phenolic compounds inhibited α-amylase activity through a mixed competitive inhibition mechanism, with the inhibition potency ranked as follows: quercetin > epicatechin > gallic acid > isoquercitrin > naringenin. The spectroscopic analysis and molecular dynamics simulations confirmed that five phenolic compounds interacted with the amino acid residues of α-amylase through hydrogen bonding and hydrophobic interactions, caused α-amylase static fluorescence quenching, and altered its conformation and microenvironment. This study provides a better understanding of the interaction mechanisms between ES starch and polyphenols, and supports the development of ES as a food that lowers sugar levels.

Aromatase as a novel target of parabens in human and rat placentas: 3D-quantitative structure-activity relationship and docking analysis

Aromatase (CYP19A1), a pivotal enzyme in the biosynthesis of estradiol from testosterone, is predominantly expressed in reproductive tissues including placentas. This study investigated the effects of paraben acid and nine parabens on the activity of human and rat CYP19A1 using microsomes derived from human and rat placentas and on estradiol secretion in human choriocarcinoma BeWo cells. The results showed that propyl, butyl, hexyl, heptyl, and nonyl parabens significantly inhibited human CYP19A1 activity, with IC50 values of 66.37, 61.08, 55.65, 48.26, and 27.24 μM, respectively. In BeWo cells, these parabens notably diminished estradiol secretion at concentrations of 100 μM. Similarly, rat CYP19A1 was inhibited by these parabens, with IC50 values of 98.07, 70.10, 41.30, 27.93, and 6.33 μM for propyl, butyl, hexyl, heptyl, and nonyl parabens, respectively. Kinetic analysis identified these compounds as mixed inhibitors. Bivariate correlation analysis revealed a negative correlation between the partition coefficient value, molecular weight, the number of carbon atoms in the alcohol moiety, as well as heavy atom number and IC50 values. Three-dimensional quantitative structure-activity relationship analysis highlighted the critical role of hydrophobic regions in determining inhibitory potency. Docking studies suggested that parabens interact with the heme-iron binding site of both human and rat CYP19A1. This study elucidates the inhibitory effects of various parabens on CYP19A1 and their binding mechanisms, thereby providing a deeper understanding of their potential impact on estrogen biosynthesis.

Experimental and computational analysis of poly(4-vinyl pyridine) and polyvinylpyrrolidone as effective corrosion inhibitors for low carbon steel in sulfuric acid

This study investigates the inhibitory effects of poly(4-vinyl pyridine) (P4VP) and polyvinylpyrrolidone (PVP) on the corrosion of low carbon steel (LCSt) in 1 M H2SO4. Protection efficacy (%PE) was measured using mass loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Results showed %PE values increased with higher polymer concentration and lower temperature. At 450 mg/L, %PE reached 93.13% and 94.19% for P4VP and PVP, respectively. These polymers function as mixed inhibitors, adsorbing onto the LCSt surface per Langmuir’s model as a mode of physical adsorption. EIS indicated that higher polymer concentration increased charge transfer resistance and decreased effective double-layer capacitance. Both P4VP and PVP also reduced pitting corrosion in chloride-containing solutions. Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) optimized the molecular structures of the inhibitors, evaluating electronic parameters such as frontier molecular orbital (FMO) energies, energy gap, softness, hardness, electron transfer fraction, dipole moment, and hyperpolarizability ( β ° ). Monte Carlo (MC) and molecular dynamics (MD) simulations provided insights into adsorption mechanisms, corroborating experimental findings and highlighting the effect of protonation. This comprehensive study enhances our understanding of the relationship between molecular structure and function in polymer inhibitors, improving their application in corrosion protection.

Mechanistic in vitro study of the effect of Cucurbita moschata (Cucurbitaceae) on carbohydrate digestive enzymes.

Diabetes is marked by postprandial hyperglycemia (PHG), an abnormal rise in blood glucose after meals. A key therapeutic goal to reduce PHG is the inhibition of α-amylase (αAM) and α-glucosidase (αGL), enzymes that break down carbohydrates into sugars. Cucurbita moschata has been shown to inhibit both enzymes. However, its inhibition mechanism has not been explored. This study investigated the in vitro inhibition mechanisms of αAM and αGL and conducted a metabolomic analysis of C. moschata (edible part) water-extract (CME), aiming to preliminarily identify its bioactive compounds (BCs). The inhibitory mechanisms were determined using Lineweaver-Burk plots. The BCs were identified and quantified using HPLC-QTOF-MS, employing both targeted and untargeted metabolomic approaches. CME had a significant higher effect (p<0.05) on αAM activity than against αGL with IC50 of 28.99 and 698.42mg/mL, respectively. The extract showed mixed and uncompetitive type inhibitions on αAM and αGL, respectively. The lowest inhibition constant (Ki) was 47.68mg/mL on αAM activity at 20mg/mL. Untargeted metabolic profiling by UPLC-MS-ESI-QTOF putatively identified 30 compounds in CME, such as amino acids, vitamins, phytohormones, fatty acids, cucurbitacins and phenolic acids, and flavonoids. Functional analysis of CME identified significant pathways, including pantothenate and CoA biosynthesis and phenylpropanoids, among others. The targeted analysis by UPLC-MS-ESI-QqQ allowed us to identify 12 compounds, with l-phenylalanine, p-hydroxybenzoic, and p-coumaric acid as majors. This study demonstrated the inhibitory potential of CME on αAM and αGL activities, which may be attributed to its metabolites. Thus, this plant represents a valuable source of BC against PHG. Practical Application: The research highlights that Cucurbita moschata has significant potential in managing postprandial hyperglycemia in diabetic patients by inhibiting enzymes like α-amylase and α-glucosidase. In addition, the identification of its compounds emphasizes its importance as a source of bioactive compounds. Therefore, C. moschata could be effectively utilized in the development of nutraceuticals or as an ingredient in functional foods specifically designed for postprandial hyperglycemia management. Thus, integrating C. moschata as part of the daily diet could offer patients with diabetes a natural alternative to control their blood glucose levels after eating.

Assessing the Potential of 1,2,3-Triazole-Dihydropyrimidinone Hybrids Against Cholinesterases: In Silico, In Vitro, and In Vivo Studies.

Combining the pharmacological properties of the 1,2,3-triazole and dihydropyrimidinone classes of compounds, two small families of mono- and di(1,2,3-triazole)-dihydropyrimidinone hybrids, A and B, were previously synthesized. The main objective of this work was to investigate the potential anti-Alzheimer effects of these hybrids. The inhibitory activities of cholinesterases (AChE and BuChE), antioxidant activity, and the inhibitory mechanism through in silico (molecular docking) and in solution (STD-NMR) experiments were evaluated. The 1,2,3-triazole-dihydropyrimidinone hybrids (A and B) showed moderate in vitro inhibitory activity on eqBuChE (IC50 values between 1 and 58.4 μM). The best inhibitor was the hybrid B4, featuring two 1,2,3-triazole cores, which exhibited stronger inhibition than galantamine, with an IC50 of 1 ± 0.1 μM for eqBuChE, through a mixed inhibition mechanism. Among the hybrids A, the most promising inhibitor was A1, exhibiting an IC50 of 12 ± 2 µM, similar to that of galantamine. Molecular docking and STD-NMR experiments revealed the key binding interactions of these promising inhibitors with BuChE. Hybrids A and B did not display Artemia salina toxicity below 100 μM.

Mitigation effect of a biodegradable surfactant N,N,N-trimethyl-2-(((hexadecyloxy)carbonyl)oxy)ethan-1-aminiumiodide for mild steel corrosion in 5% HCl: Experimental and theoretical insights

A cleavable cationic surfactant having carbonate linkage, N,N,N-trimethyl-2-(((hexadecyloxy)carbonyl)oxy)ethan-1-aminiumiodide referred to as THC was synthesised and characterized employing elemental analysis, FT-IR (Fourier Transform Infrared Spectroscopy), 1H NMR (Nuclear Magnetic Resonance) and 13C NMR. The extent of corrosion inhibition of THC was for the first time studied experimentally and theoretically on mild steel (MS) substrate in 5 % HCl solution at temperatures 303, 313, 323, 333, 343, 353 K. Experimental investigations include gravimetric analysis, potentiodynamic polarization (PDP) and electrochemical impedance analysis (EIS). THC provided maximum inhibition efficiency of 93.2 % at concentration of 1×10−4 M at 303 K which was further raised to 98.1 % at 353 K. PDP studies reveal that given surfactant is mixed type inhibitor. Surface studies such as contact angle measurement, AFM (Atomic Force Microscopy), SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Analysis), and XPS (X-ray Photoelectron Spectroscopy) were employed to justify the adsorption of inhibitor molecules on MS surface. Furthermore, biodegradability test on THC was done to support the environment friendly nature of the surfactant.

Corrosion kinetics of carbon steel in hydrochloric acid and its inhibition by recycling Salbutamol extracted from expired Farcolin drug

ABSTRACT Salbutamol, which has nontoxic properties, was effectively extracted from expired Farcolin and was evaluated as an inhibitor against carbon steel (CSt) dissolution in 1.0 M HCl solution. Some technologies were applied to determine the inhibition efficacy of Salbutamol such as weight loss (WL), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Also, FTIR, 1HNMR, and mass spectroscopy were used to clarify the structure of Salbutamol. The findings indicate that CSt can profit significantly from the recycling of Farcolin medicine and that Salbutamol may be extracted and employed as a CSt corrosion inhibitor. The efficiency of the inhibition improved with an increase in the dosage of salbutamol, polarization resistance and lowering corrosion current density, WL, and temperature. It’s reached 89.65% at a dose of 200 ppm using the EIS technology. The inhibition impact of Salbutamol was interpreted due to its spontaneous adsorption on the CSt/electrolyte interface, in accordance with Langmuir isotherm. Salbutamol was classified as a mixed inhibitor. In addition, how temperature affects the corrosion rate is considered by calculating and discussing some thermodynamic parameters.

Investigation of ponatinib metabolism and drug-drug interactions with lycopene and shikonin in vitro and invivo

Ponatinib is approved for use in patients with chronic myeloid leukemia (CML) who are resistant to or intolerant to prior tyrosine kinase inhibitor (TKI) therapy. Given that ponatinib can induce significant cardiotoxicity when taken, and that most Chinese medicines have cardioprotective effects, it is possible to administer them in combination in clinic to alleviate adverse effects. The quantitative determination of ponatinib and its metabolite N-desmethyl ponatinib was optimized and fully verified by ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). And the drug-drug interactions (DDI) of ponatinib with lycopene and shikonin, both in vivo and in vitro, were studied. The results of bioanalytical methodology showed that ponatinib and N-desmethyl ponatinib had good linearity in plasma samples, and their selectivity, accuracy, precision, stability, matrix effect and recovery were all satisfied with the need of quantitative analysis of samples. In animal experiments, compared with the control group, lycopene and shikonin significantly changed the pharmacokinetic parameters of ponatinib, including AUC(0-t), AUC(0-∞) and CLz/F, while having no effect on the pharmacokinetic parameters of N-desmethyl ponatinib. In vitro interaction studies indicated that lycopene showed mixed inhibition mechanism on ponatinib metabolism in both rat liver microsomes (RLM) and human liver microsomes (HLM). And, shikonin displayed mixed inhibition mechanism in RLM and competitive inhibition mechanism in HLM, respectively. In summary, the UPLC-MS/MS method can accurately and sensitively quantify ponatinib and N-desmethyl ponatinib, and provide further reference for clinical drug combination between ponatinib and lycopene or shikonin.

Mechanistic insights into β-glucuronidase inhibition by isoprenylated flavonoids from Centaurea scoparia: Bridging experimental and computational approaches

Exploring the intricate mechanisms underlying the inhibition of β-glucuronidase, particularly the enzyme produced by gastrointestinal bacteria, is essential for the development of novel therapeutic interventions and pharmaceutical advancements. Inhibiting bacterial β-glucuronidase can prevent the reactivation of harmful drug metabolites in the gut, thereby reducing associated toxicities. The inhibitory potential of four isoprenylated flavonoids from Centaurea scoparia against β-glucuronidase was intensively investigated by combined in vitro and in silico tools. The results of in vitro inhibitory activity showed that Compounds 1 and 3 exhibited the highest inhibitory activity, as evidenced by their low IC50 values of 3.65 ± 0.28 and 3.97 ± 0.11 μM, respectively. The enzyme kinetics analysis revealed that Compound 1 and the positive control drug (EGCG) follow a mixed inhibition mechanism. In contrast, compounds 3 and 4 exhibited a noncompetitive inhibition mode, as suggested by the intersection patterns observed in the Lineweaver-Burk plots. The docking studies corroborated the in vitro inhibitory assay results, with Compounds 1 and 3 demonstrating the lowest binding affinities and the highest extent of polar and hydrophobic interactions with residues in the enzyme's binding site. Utilizing a 200 ns molecular dynamics (MD) simulation, we examined the interaction dynamics between isolated flavonoids and β-glucuronidase. The analysis of multiple MD parameters revealed that compounds 1 and 3 maintained consistent trajectories and demonstrated significant energy stabilization when interacting with β-glucuronidase. These computational findings align with experimental results, highlighting the potential of compounds 1 and 3 as potent inhibitors for β-glucuronidase.

Exploring the performance of Coriandrum sativum extract as an effective corrosion inhibitor for mild steel in a [formula omitted] medium, and its sustainable application in the eco-friendly removal of heavy metals

This research investigated the performance of coriander seeds, for the first time, in two critical phenomena: wastewater treatment and corrosion inhibition in acidic environments. On one hand, the aqueous extracts from Coriandrum sativum seeds (CE) were evaluated for mild steel corrosion inhibition in a 2.0 M phosphoric acid medium using several techniques such as phytochemical analysis (GC-MS), potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy (SEM-EDAX) and theoretical analyses, including DFT calculations and Molecular Dynamic Simulations, further elucidated the major chemical components. First, the phytochemical analysis has proved that CE contains heteroatoms. Second, the electrochemical results indicate that CE behaves as a mixed type inhibitor and the corrosion reaction is controlled by charge transfer process. Finally, The theoretical calculations confirmed that the active compounds of CE can be adsorbed on the Fe (1 1 0) surface through physical patterns and by sharing charges with iron to form coordinate bonds. The acquired results have shown a strong correlation between corrosion inhibition efficiency that was about 93 %, SEM-EDAX and DFT parameters. On the other hand, the study examined coriander seeds (CS) in powder form as a removal of copper ions in aqueous solutions through Atomic Absorption Spectroscopy and Inductively Coupled Plasma analysis. The parametric study was effectuated by establishing the effect of contact time, adsorbent mass, solution pH and stirring speed. The removal rate was about 79 %. Regeneration studies showed that CS could be reused for five cycles without significant loss of effectiveness. SEM-EDAX analysis has proved the studied process.

Design, synthesis and biological evaluation of novel benzocoumarin derivatives as potent inhibitors of MAO-B activity

The continued research of novel reversible inhibitors targeting monoamine oxidase (MAO) B remains crucial for effectively symptomatic treatment of Parkinson’s disease. In this study we synthesized and evaluated a new series of 3-aryl benzo[g] and benzo[h] coumarin derivatives as MAO-B inhibitors. Compound A6 has been found to display the most potent inhibitory activity and selectivity against the MAO-B isoform (IC50 = 13 nM and SI = >7693.31 respectively). Inhibition mode of A6 on MAO-B was predicted as mixed reversible inhibition with a Ki value of 3.274 nM. Furthermore, in order to elaborate structure–activity relationships, the binding mode of A6 was investigated by molecular docking simulations.

Corrosion inhibition of tetrabutylphosphonium benzotriazolate on carbon steel in acidic medium

The inhibition effect of tetrabutylphosphonium benzotriazolate (TBPB) on carbon steel in a 1 mol·L−1 HCl solution was investigated using a combination of analytical techniques, including polarization curve, electrochemical impedance spectroscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The study revealed that TBPB acts as a mixed corrosion inhibitor for carbon steel in acidic conditions. The efficiency of corrosion inhibition was observed to increase gradually with rising TBPB concentrations, reaching a maximum of 92 % at a concentration of 10 mmol·L−1. This enhancement in corrosion inhibition efficiency is attributed to the adsorption of TBPB on the metal surface, effectively isolating it from the corrosive medium and thereby preventing corrosion reactions. Importantly, this mechanism aligns well with the Langmuir isothermal adsorption model.

Synergistic inhibition effect of diolefinic dye and silver nanoparticles for carbon steel corrosion in hydrochloric acid solution

The current work looks at the inhibitory effects of a diolefinic dye, namely 1,4-bis((E)-2-(3-methyl-2,3-dihydrobenzo[d]thiazol-2-yl) vinyl) benzene iodide salt, in relation to CS corrosion mitigation in hydrochloric acid (HCl) environment. This study uses a variety of experimental methodologies, including weight loss (WL) analysis, electrochemical tests, and theoretical considerations. The synergistic effect of diolefinic dye and AgNPs on the corrosion inhibition of CS in 1 M HCl was investigated. The inhibition efficiency (IE) displays a notable enhancement as the concentration of the dye is elevated and as the temperature raises the IE increases. The diolefinic dye exhibited % IE of 83% even at low concentration (1 × 10–4 M) whereas 90% in the presence of (2.26 × 10–10) AgNPs. Tafel graphs demonstrate that the dye follows a mixed type inhibitor. The adsorption of the dye on CS surface follows Langmuir model. Moreover, the influence of temperature and the activation parameters disclose that diolefinic dye is chemisorbed on the CS surface. The synergistic coefficient of the diolefinic dye and AgNPs under various concentration conditions was greater than unity. The surface morphology of CS sheets was confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Density Functional Theory (DFT) calculations provide theoretical support for the inhibitory effects of the examined dye. Notably, there is a high agreement between the findings of practical studies and theoretical expectations.

Corrosion inhibitor from nature: Fundamentals of tannic acid inhibition for AA2024 alloy

This study addresses the fundamentals of corrosion inhibition of AA2024 alloy by tannic acid (TA), a Cr-free and eco-friendly natural product. To this end, the AA2024 alloy was immersed in NaCl solution (50 mM) with different TA concentrations (0.1–10 mM) for 7 days. Surface (SEM, Raman, and SKPFM) and electrochemical analyses (EIS, PDP, and SVET) revealed mixed inhibition after 1 day of immersion in TA solution. Long-term immersion tests in TA solutions produced a tannate-rich oxide film on the surface. The films with low tannate content (formed in 0.1 and 1 mM TA) showed the highest stability and corrosion resistance.

Xanthine oxidase inhibitors: Virtual screening and mechanism of inhibition studies

Xanthine oxidase (XO), which plays a key role in purine metabolism, is an important target enzyme for the prevention and treatment of hyperuricemia. Inhibitory activity against XO is a common criterion for the screening of compounds with potential anti-hyperuricemic activity. In this study, 22 XO inhibitors were used to construct a 3D-QSAR pharmacophore model. Subsequently, molecular docking and in vitro activity evaluations were used to identify strong XO inhibitors from a list of 2000 natural compounds. The interaction mechanisms of these compounds with XO were analyzed based on inhibition kinetics and multi-spectral analyses. The pharmacophore model was composed of three hydrogen bond receptors and a hydrophobic center. The screened compounds — Diosmetin, Fisetin, and Genistein — all showed good XO inhibitory activity, with IC50 values of 1.86 ± 0.11 μM, 5.83 ± 0.08 μM, and 7.56 ± 0.10 μM, respectively. Kinetic analysis, fluorescence quenching assays, and molecular docking experiments showed that Diosmetin, Fisetin, and Genistein docked near the same active site of XO, mainly affecting the microenvironment of tryptophan residues. These molecules showed static binding to XO via hydrogen bonds, hydrophobic interactions, and van der Waals forces. Diosmetin and Genistein were competitive inhibitors, whereas Fisetin was a mixed inhibitor. Infrared spectroscopy showed that Diosmetin, Fisetin, and Genistein increased the α-helix content of XO from 7.4 % to 16.6 %, 21.4 %, and 11.2 %, respectively, thereby enhancing its stability. In summary, the pharmacophore model constructed in this study was accurate. The flavonoids Diosmetin, Fisetin, and Genistein effectively inhibited the activity of XO, and the amino acid residues LEU257, ILE353, and VAL259 played a key role in the interaction between the flavonoids and XO. These findings are of great significance for the screening and development of new XO inhibitors.