Mixed-type Inhibitor Research Articles

Kinetic characterization and phylogenetic analysis of human ADP-dependent glucokinase reveal new insights into its regulatory properties

Although ADP-dependent sugar kinases were first described in archaea, at present, the presence of an ADP-dependent glucokinase (ADP-GK) in mammals is well documented. This enzyme is mainly expressed in hematopoietic lineages and tumor tissues, although its role has remained elusive. Here, we report a detailed kinetic characterization of the human ADP-dependent glucokinase (hADP-GK), addressing the influence of a putative signal peptide for endoplasmic reticulum (ER) destination by characterizing a truncated form. The truncated form revealed no significant impact on the kinetic parameters, showing only a slight increase in the Vmax value, higher metal promiscuity, and the same nucleotide specificity as the full-length enzyme. hADP-GK presents an ordered sequential kinetic mechanism in which MgADP is the first substrate to bind and AMP is the last product released, being the same mechanism described for archaeal ADP-dependent sugar kinases, in agreement with the protein topology. Substrate inhibition by glucose was observed due to sugar binding to nonproductive species.Although Mg2+ is an essential component for kinase activity, it also behaves as a partial mixed-type inhibitor for hADP-GK, mainly by decreasing the MgADP affinity. Regarding its distribution, phylogenetic analysis shows that ADP-GK's are present in a wide diversity of eukaryotic organisms although it is not ubiquitous. Eukaryotic ADP-GKs sequences cluster into two main groups, showing differences in the highly conserved sugar-binding motif reported for archaeal enzymes [NX(N)XD] where a cysteine residue is found instead of asparagine in a significant number of enzymes. Site directed mutagenesis of the cysteine residue by asparagine produces a 6-fold decrease in Vmax, suggesting a role for this residue in the catalytic process, probably by facilitating the proper orientation of the substrate to be phosphorylated.

Corrosion inhibition of aluminium in 0.3 M HCl using starch mucor in potassium iodide as inhibitor

Purpose The purpose of this study is to investigate starch mucor (SM) in potassium iodide (KI) as corrosion inhibitor of aluminium in hydrochloric acid (HCl) medium. Design/methodology/approach The SM in KI was characterized by gravimetric, scanning electron microscopy, electrochemical impedance spectroscopy measurements, potentiodynamic polarization and gas chromatography-mass spectrometer techniques. The inhibition efficiency was optimized using response surface methodology. Findings The result revealed that the inhibitor inhibited corrosion at a low concentration with the rate of inhibition increasing as the concentration of the inhibitor increased. The inhibition efficiency increases as the temperature was increased with slight incorporation of the inhibitor (SM in KI). This indicates that the corrosion control is both inhibitor (SM in KI) and temperature dependent. Originality/value The research results can provide the basis for using SM in KI as corrosion inhibitor of aluminium in HCL medium. Mixed-type inhibitor nature of SM was proved by cathodic and anodic nature of the polarization curves.

Elsholtzia Griffithii as an eco-friendly anticorrosive inhibitor of Mild Steel under Acid Medium

Anticorrosion analysis of Elsholtzia Griffithii extract on Mild Steel (MS) in H2SO4 medium was experimented with through Gravimetric Method, Potentiodynamic Polarization, Electrochemical Impedance Spectroscopy (EIS) at room temperature. Results of the assessment showed that Elsholtzia Griffithii inhibits the corrosion of MS and the rate of corrosion is significantly reduced on increasing its concentration. Elsholtzia Griffithii exhibits the rise in its anticorrosive efficiency from 82.0% to 95.0% when the extract's concentration altered from 125 mg/L to 1000 mg/L. The variation in Ecorr value is within 85 mV, revealing Elsholtzia Griffithii as a mixed-type inhibitor. The change of charge transfer resistance (Rct) from 4.90 Ω cm−1 to 96.92 Ω cm−1 with falling of double layer capacitance (Cdl) from 947.22 × 10−4 F cm−2 to 2.74 × 10−4 F cm−2 on the addition of extract is a clear indication of the mitigation of corrosion. The corrosion mitigation is caused by the adsorption of extract molecules on surface of MS and Langmuir's adsorption isotherm is obeyed in its mechanism of adsorption. The results of gravimetric and electrochemical methods are concurred by the observation of Gas Chromatography Mass spectrometry (GC-MS), Fourier transform infrared (FTIR), UV-VIS spectroscopy and Scanning electron microscopy (SEM) studies. The functional groups such as O-H, CO and CC in the extract are responsible for binding on the mild steel surface. Density Functional Theory (DFT) calculation was further carried out to validate the experimental results. All the findings suggested that Elsholtzia Griffithii is a tenable and sustainable inhibitor for corrosion of MS under acid solution.

Inhibition of Acetylcholinesterase by Novel Lupinine Derivatives.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive memory loss and cognitive impairment due in part to a severe loss of cholinergic neurons in specific brain areas. AD is the most common type of dementia in the aging population. Although several acetylcholinesterase (AChE) inhibitors are currently available, their performance sometimes yields unexpected results. Thus, research is ongoing to find potentially therapeutic AChE inhibitory agents, both from natural and synthetic sources. Here, we synthesized 13 new lupinine triazole derivatives and evaluated them, along with 50 commercial lupinine-based esters of different carboxylic acids, for AChE inhibitory activity. The triazole derivative 15 [1S,9aR)-1-((4-(4-(benzyloxy)-3-methoxyphenyl)-1H-1,2,3-triazol-1-yl)methyl)octahydro-2H-quinolizine)] exhibited the most potent AChE inhibitory activity among all 63 lupinine derivatives, and kinetic analysis demonstrated that compound 15 was a mixed-type AChE inhibitor. Molecular docking studies were performed to visualize interaction between this triazole derivative and AChE. In addition, a structure-activity relationship (SAR) model developed using linear discriminant analysis (LDA) of 11 SwissADME descriptors from the 50 lupinine esters revealed 5 key physicochemical features that allowed us to distinguish active versus non-active compounds. Thus, this SAR model could be applied for design of more potent lupinine ester-based AChE inhibitors.

Some Brassicaceae Extracts as Potential Antioxidants and Green Corrosion Inhibitors.

Glucosinolates-rich extracts of some Brassicaceae sources, such as broccoli, cabbage, black radish, rapeseed, and cauliflower, were obtained using an eco-friendly extraction method, in a microwave field, with 70% ethanol, and evaluated in order to establish their in vitro antioxidant activities and anticorrosion effects on steel material. The DPPH method and Folin-Ciocâlteu assay proved good antioxidant activity (remaining DPPH, 9.54-22.03%) and the content of total phenolics between 1008-1713 mg GAE/L for all tested extracts. The electrochemical measurements in 0.5 M H2SO4 showed that the extracts act as mixed-type inhibitors proving their ability to inhibit corrosion in a concentration-dependent manner, with a remarkable inhibition efficiency (92.05-98.33%) achieved for concentrated extracts of broccoli, cauliflower, and black radish. The weight loss experiments revealed that the inhibition efficiency decreased with an increase in temperature and time of exposure. The apparent activation energies, enthalpies, and entropies of the dissolution process were determined and discussed, and an inhibition mechanism was proposed. An SEM/EDX surface examination shows that the compounds from extracts may attach to the steel surface and produce a barrier layer. Meanwhile, the FT-IR spectra confirm bond formation between functional groups and the steel substrate.

Design, Synthesis, In Vitro, and In Silico Insights of 5-(Substituted benzylidene)-2-phenylthiazol-4(5H)-one Derivatives: A Novel Class of Anti-Melanogenic Compounds.

(Z)-5-Benzylidene-2-phenylthiazol-4(5H)-one ((Z)-BPT) derivatives were designed by combining the structural characteristics of two tyrosinase inhibitors. The double-bond geometry of trisubstituted alkenes, (Z)-BPTs 1-14, was determined based on the 3JC,Hβ coupling constant of 1H-coupled 13C NMR spectra. Three (Z)-BPT derivatives (1-3) showed stronger tyrosinase inhibitory activities than kojic acid; in particular, 2 was to be 189-fold more potent than kojic acid. Kinetic analysis using mushroom tyrosinase indicated that 1 and 2 were competitive inhibitors, whereas 3 was a mixed-type inhibitor. The in silico results revealed that 1-3 could strongly bind to the active sites of mushroom and human tyrosinases, supporting the kinetic results. Derivatives 1 and 2 decreased the intracellular melanin contents in a concentration-dependent manner in B16F10 cells, and their anti-melanogenic efficacy exceeded that of kojic acid. The anti-tyrosinase activity of 1 and 2 in B16F10 cells was similar to their anti-melanogenic effects, suggesting that their anti-melanogenic effects were primarily owing to their anti-tyrosinase activity. Western blotting of B16F10 cells revealed that the derivatives 1 and 2 inhibited tyrosinase expression, which partially contributes to their anti-melanogenic ability. Several derivatives, including 2 and 3, exhibited potent antioxidant activities against ABTS cation radicals, DPPH radicals, ROS, and peroxynitrite. These results suggest that (Z)-BPT derivatives 1 and 2 have promising potential as novel anti-melanogenic agents.

Surface interaction and corrosion inhibition of carbon steel in sulfuric acid using Petroselinum crispum extract

With the aid of the mass loss (ML) method, and a few electrochemical techniques [potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)], the inhibitory impact of Petroselinum crispum (PC) extract on C-steel corrosion in solutions of 1 M sulfuric acid was assessed. By employing Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques, the C-steel surface morphology was investigated. The data showed that the solution of plant extract can be effectively utilized to inhibit C-steel corrosion in solutions of 1 M sulfuric acid. The effectiveness of the extract was enhanced by the higher extract dose and rising temperature. The apparent activation energy and the enthalpy of the dissolution process were determined and discussed. The presence of PC decreases the double-layer capacity from 493.1 to 107.3 μF cm−2 and raises the charge transfer resistance in a solution of 1 M sulfuric acid from 43.39 to 287.7 Ω cm2. PC is a mixed-type inhibitor, as demonstrated by PDP tests. The PC extract demonstrated the highest productivity for the C-steel protection up to 90.2% at 300 ppm from the extract, according with the PDP technique. The attained data indicated that PC extract was adsorbed chemically (ΔGoads > 40 kJ mol−1) onto the surface of the C-steel following the Temkin isotherm. The results of numerous tests appear to agree.

Acetylcholinesterase inhibitory activity of modified lupane, oleanane, and ursane A-seco-triterpenoids.

A series of new lupane, ursane, and oleanane type triterpenic A-seco-derivatives containing bromo-, azido-, alkyne-, 1H-tetrazol-5-yl-, 5-methyloxazol-2-yl-, N-(4-(4-methylpiperazin-1-yl)but-2-yn-1-yl), and a carbonyl group at C2, C24, C28, C30 positions has been synthesized. The bioactivity was evaluated by Ellman's method, and the results showed that most of the compounds displayed moderate acetylcholinesterase inhibitory activities in vitro. Among them, A-seco-derivatives of 28-oxo-allobetuline and betulinic acid with bromo- and azido-groups exhibited the most potent inhibitory activity against AChE. Extra experiments showed methyl 2-cyano-3,4-seco-dibromo- and 2-cyano-3,4-seco-diazido-derivatives of betulinic acid as mixed-type inhibitors, with Ki values as low as Ki = 0.18 µM and Ki = 0.21 µM, respectively.

Two novel Schiff bases derived from 3-amino-1,2,4-triazole as corrosion inhibitors for carbon steel pipelines during acidizing treatment of oil wells: Laboratory and theoretical studies

ABSTRACT Two novel Schiff bases derivatives of 1 H–1,2,4-triazole-3-yl)imino (L1 and L2) were synthesized and investigated as corrosion inhibitors for carbon steel in 1 M HCl solution. The corrosion inhibition efficiency of L1 and L2 was inspected by gravimetric measurements, electrochemical method, and quantum chemical calculations. L1 and L2 inhibitory efficiency is related to the test’s concentration. The created compounds were characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analysis. The corrosion inhibition property of the synthesized Schiff base on carbon steel, the main component of pipelines used in oil and gas fields, in 1 M HCl medium was investigated using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). From the loss-weight data it was found the inhibition rises by the grown inhibitor concentration, which at 1 mM of L1 and L2, receiving a record level in η w of 92.3% and 93.9%, respectively. The prepared Schiff bases act as good mixed-type corrosion inhibitors, according to potentiodynamic polarization experiments. Both inhibitors’ adsorption on CS surfaces followed the Langmuir adsorption isotherm, with both physisorption and chemisorption. The impact of the molecular structure of the synthesized Schiff bases was examined using the density-functional theory (DFT) method and molecular dynamic (MD) simulation.

Synthesis and anti-Alzheimer potential of novel α-amino phosphonate derivatives and probing their molecular interaction mechanism with acetylcholinesterase

Pleiotropic interference may be a prerequisite for the efficient limitation of the progression of multi-factorial diseases such as Alzheimer's disease (AD). Concept of designing the single chemical entity acting on two or more targets of interest has potential advantage in AD therapy. In line with this, rational design and synthesis of frame work of hybrids bearing 2,3-disubstituted quinazolinone, vanillin and α-amino phosphonate scaffolds (5a─v) were carried out. A congeneric set of twenty-two synthetic derivatives (5a─v) were evaluated for their cholinesterase inhibitory, antioxidant, DNA nicking, DNA protection, neuroprotective and Aβ aggregation modulatory activities. Amongst tested activities, the most significant and worth mentioning is that the analogues 5m, 5p and 5u were found to be the most potent, selective, and mixed type inhibitors of EeAChE with IC50 values of 0.296 ± 0.030, 0.289 ± 0.027, and 0.306 ± 0.028 μM, respectively. Further, the biophysical approaches indicated that the compounds 5m, 5p, and 5u have a strong binding affinity towards AChE. Kinetic and Molecular docking studies have revealed that the most active congeners were well oriented in the AChE active site by interacting with both catalytic active site (CAS) and peripheral anionic site (PAS). A few parameters derived from molecular dynamics (MD) simulation trajectories emphasized the stability of AChE-5p and 5m complexes throughout the 100 ns simulations, and the local conformational changes of the residues of AChE validate the stability of AChE-5p and 5m complexes. Further, these derivatives significantly impacted ABTS radical scavenging capacities and maximal DNA protection activity. Importantly, Thioflavin T (ThT) assay and FE-SEM study demonstrated compounds 5m, 5p and 5u as effective Aβ1−42 fibril modulators at molecular level by the formation of micro size co-assembled mature structures, thus efficiently abolishing the cytotoxicity of Aβ1–42. Finally, these active compounds are determined to be non-toxic and highly neuroprotective against H2O2-induced cell death in SK-N-SH cell lines. Furthermore, in silico ADMET prediction studies have revealed that the targeted analogues satisfied most of the characteristics of CNS acting drugs. These multi-functional efficacies indicated worthiness of these α-amino phosphonate derivatives being chosen for further pharmacokinetics, toxicity, and behavioral research to test their potential for AD treatment.

Inhibition Analysis and High-Resolution Crystal Structure of Mus musculus Glutathione Transferase P1-1.

Multidrug resistance is a significant barrier that makes anticancer therapies less effective. Glutathione transferases (GSTs) are involved in multidrug resistance mechanisms and play a significant part in the metabolism of alkylating anticancer drugs. The purpose of this study was to screen and select a lead compound with high inhibitory potency against the isoenzyme GSTP1-1 from Mus musculus (MmGSTP1-1). The lead compound was selected following the screening of a library of currently approved and registered pesticides that belong to different chemical classes. The results showed that the fungicide iprodione [3-(3,5-dichlorophenyl)-2,4-dioxo-N-propan-2-ylimidazolidine-1-carboxamide] exhibited the highest inhibition potency (ΙC50 = 11.3 ± 0.5 μΜ) towards MmGSTP1-1. Kinetics analysis revealed that iprodione functions as a mixed-type inhibitor towards glutathione (GSH) and non-competitive inhibitor towards 1-chloro-2,4-dinitrobenzene (CDNB). X-ray crystallography was used to determine the crystal structure of MmGSTP1-1 at 1.28 Å resolution as a complex with S-(p-nitrobenzyl)glutathione (Nb-GSH). The crystal structure was used to map the ligand-binding site of MmGSTP1-1 and to provide structural data of the interaction of the enzyme with iprodione using molecular docking. The results of this study shed light on the inhibition mechanism of MmGSTP1-1 and provide a new compound as a potential lead structure for future drug/inhibitor development.

Temperature Effect on the Corrosion Inhibition of Carbon Steel by Polymeric Ionic Liquids in Acid Medium

In the present research work, the temperature effect on the corrosion inhibition process of API 5L X60 steel in 1 M H2SO4 by employing three vinylimidazolium poly(ionic liquid)s (PILs) was studied by means of electrochemical techniques, surface analysis and computational simulation. The results revealed that the maximal inhibition efficiency (75%) was achieved by Poly[VIMC4][Im] at 308 K and 175 ppm. The PILs showed Ecorr displacements with respect to the blank from -14 mV to -31 mV, which revealed the behavior of mixed-type corrosion inhibitors (CIs). The steel micrographs, in the presence and absence of PILs, showed less surface damage in the presence of PILs, thus confirming their inhibiting effect. The computational studies of the molecular orbitals and molecular electrostatic potential of the monomers suggested that the formation of a protecting film could be mainly due to the nitrogen and oxygen heteroatoms present in each structure.

Corrosion inhibition effect of 1-phenyl-5-mercaptotetrazole on nickel-aluminum bronze in seawater: A combined experimental and theoretical study

A combined experimental and theoretical study was performed on corrosion inhibition effect of 1-Phenyl-5-mercaptotetrazole (PMT) on nickel-aluminum bronze (NAB) in seawater. Gravimetric measurement and electrochemical method, such as the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), Tafel polarization curve were used to verify the corrosion inhibition effect of PMT. It was found that the corrosion inhibition efficiency (IE) of PMT achieved 94.4 %, 99.5 %, 98.7 % at a concentration of 1.12 mM, respectively. The slump of the degree of corrosion on NAB surface was also revealed based on SEM and AFM images analysis with the addition of PMT. According to the Langmuir isotherm model based on EIS, PMT was confirmed as a mixed-type corrosion inhibitor between −20 kJ mol–1 and −40 kJ mol–1. Besides, the successful adsorption of PMT on NAB has been revealed by the results of XPS and the change of water contact angle on NAB surface. In combination XPS with quantum chemistry calculations, PMT molecules are adsorbed on the surface of NAB by the active S atom and the tetrazole ring as the major adsorption groups, thus, the protective barrier formed by PMT on the surface of NAB can effectively insulate NAB from contact with seawater. The research results in this paper have showed that PMT as a drug intermediate has an excellent corrosion inhibition effect on the NAB at extremely low concentration in seawater.

Synthesis and biological evaluation of substituted acetamide derivatives as potential butyrylcholinestrase inhibitors

Alzheimer’s disease (AD) is the most common type of age-related dementia. Inhibition of butyrylcholinesterase (BChE) emerge as an effective therapeutic target for AD. A series of new substituted acetamide derivatives were designed, synthesized and evaluated for their ability to inhibit BChE. The bioassay results revealed that several compounds displayed attractive inhibition against BChE). Among them, compound 8c exhibited the highest BChE inhibition with IC50 values of 3.94 μM. Lineweaver Burk plot indicated that 8c acted as a mixed-type BChE inhibitor. In addition, docking studies confirmed the results obtained through in vitro experiments, and showed that 8c bound to the catalytic anionic site (CAS) and peripheral anionic site (PAS) of BChE active site. Meanwhile, its ADME parameters were approximated using in silico method. Molecular dynamics simulation studies on the complex of 8c-BChE were performed, RMSD, RMSF, Rg, SASA, and the number of hydrogen bonds were calculated as well. These results implied that 8c could serve as appropriate lead molecule for the development of BChE inhibitor.

A synthesized pyrimidine derivative with highly efficient long-term corrosion protection for API X60 steel in CO2-saturated NACE brine ID196 under hydrodynamic condition

This research investigates the CO2 corrosion inhibition characteristics of a synthesized pyrimidine derivative whose molecular structure is embellished with nitrogen-based functional groups with the intention of achieving highly effective and stable film formation, at low doses, after prolonged corrosion period under turbulent hydrodynamics. For this purpose, 5-(4-(dimethylamino)phenyl)-2,7-dithioxo-2,3,5,6,7,8-hexahydropyrimido[4,5-d]pyrimidin-4(1H)-one (DPP) was synthesized using the one-pot method, and investigated as inhibitor against the corrosion of API X60 steel after instantaneous and prolonged (72 h) immersion in CO2-saturated NACE ID196 brine under 1000 rpm rotation speed. Results from potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements show that DPP is a mixed-type inhibitor which lowers the double layer capacitance and rate of charge transfer across the steel-solution interface with 97% efficiency. Its instantaneous adsorption blocks the steel surface from any noticeable microstructural damage, based on scanning electron microscopy (SEM) characterization. After prolonged exposure (72 h), the uninhibited steel experiences enhanced resistance, which inversely depreciated the DPP efficiency to > 73%. With DPP, however, the steel is significantly protected against surface microstructural degradation, based on SEM assessment. Computational modeling with density functional theory (DFT) and molecular dynamics simulation (MDS) provided molecular-level confirmation of the experimental results.

Synthesis of N1, N2-bis [1-(pyridin-2-yl)ethylidene]oxalohydrazide and its corrosion inhibition effect on Stainless steel 304L in chloride media

N1, N2-bis [1-(pyridin-2-yl)ethylidene]oxalohydrazide inhibitor (NOL) were synthesized and evaluated as corrosion inhibitors for stainless steel 304 L (SS304L) in one molar HCl. The adsorption properties of the synthesized NOL were determined by experimental and theoretical methods in an acid environment. With the aid of chemical methods such as mass loss method (ML), DC potentiodynamic polarization (PP), and AC impedance (EIS) tests. Outcome data obtained from these methods displayed that with increasing the concentration of these substances their inhibition efficiency (%IE) increased and reached 95.7 %. The presence of NOL reduces the capacity of the double layer and improves the charge transfer resistance in a solution of 1 M hydrochloric acid. NOL is a mixed-type inhibitor, conferring to the polarization curves. The attained data indicated that NOL was chemically adsorbed onto the SS304L surface in accordance with the Temkin isotherm. The surface protection examination was carried out using scanning electron microscopy and the formation of the complex on the surface was approved using Fourier Transfer Infrared Spectroscopy (FTIR). Also, the quantum chemical parameters of NOL were computed and discussed. The results of several methods are in agreement with each other.

Corn gluten meal peptides inhibit prolyl oligopeptidase and modulate α-synuclein aggregation in KCl-treated SH-SY5Y cells

Prolyl oligopeptidase (POP) is known to be related to neurocognitive disorder as it degrades neuroactive peptides. POP inhibitory peptides from corn gluten meal hydrolysate (CGM-H) were identified and characterized. After a series of chromatographic separations, ALLTLSPLGPA was identified as the most effective POP inhibitor, with an IC50 value of 0.79 ± 0.004 mM. Its in silico gastrointestinal (GI)-digested peptide, SPLGPA, exhibited 3-fold lower POP inhibitory activity, while higher inhibition was observed in SH-SY5Y cells when compared to its parent peptide. In addition, 25 µM ALLTLSPLGPA notably reduced α-synuclein aggregation in KCl-treated SH-SY5Y cells. ALLTLSPLGPA and SPLGPA were characterized as mixed-type and uncompetitive inhibitors, respectively. They bound to POP via hydrogen bonds at the β-propeller domain. These results demonstrated that peptides derived from CGM could have potential for developing nutraceutical products targeting brain health.

Inhibitory effect of acarbose on tyrosinase: application of molecular dynamics integrating inhibition kinetics

Due to its clinical and cosmetic applications, investigators have paid attention to tyrosinase (TYR) inhibitor development. In this study, a TYR inhibition study with acarbose was investigated to gain insights into the regulation of the catalytic function. Biochemical assay results indicated that acarbose was turned to be an inhibitor of TYR in a reversible binding manner and probed as a distinctive mixed-type inhibitor via measurement of double-reciprocal kinetic (K i = 18.70 ± 4.12 mM). Time-interval kinetic measurement indicated that TYR catalytic function was gradually inactivated by acarbose in a time-dependent behavior displaying with a monophase process that was evaluated by semi-logarithmic plotting. Spectrofluorimetric measurement by integrating with a hydrophobic residue detector (1-anilinonaphthalene-8-sulfonate) showed that the high dose of acarbose derived a conspicuous local structural deformation of the TYR catalytic site pocket. Computational docking simulation showed that acarbose bound to key residues such as HIS61, TYR65, ASN81, HIS244, and HIS259. Our study extends an understanding of the functional application of acarbose and proposes that acarbose is an alternative candidate drug for a whitening agent via direct retardation of TYR catalytic function and it would be applicable for the relevant skin hyperpigmentation disorders concerning the dermatologic clinical purpose. Communicated by Ramaswamy H. Sarma

Chasew (Anacardium Occidentale) Leaves Extract as Green Corrosion Inhibitor of API 5L X52 in Acidic Media

Chasew leaves extract has been investigated as green corrosion inhibitor to inhibit the corrosion process of API 5L X52 in acidic media. The inhibition effect of cashew leaves was analyzed using electrochemical measurement such as Tafel Polarization and Electrochemical Impedance Spectroscopy (EIS). FTIR, polyphenol content and phytochemical analysis were also employed to ensure the chemical compound of cashew leaves extract. Concentration of cashew leaves extract was varied for electrochemical measurement i.e. 0, 100, 200, 300, 400 and 500 ppm. Furthermore, immersion time variation (0, 30 and 60 min) was used prior to electrochemical measurement. The electrochemical measurement results indicate that cashew leaves extract work effectively as green corrosion inhibitor of API 5L X52 in acidic media. The performance of this green corrosion inhibitor was optimum at concentration of 500 ppm and 60 min of immersion time. Cashew leaves extract was mixed-type inhibitor because the corrosion potential value shifted less than 85 mV. The Increasing of surface resistance value and the decreasing in the capacitance of double layer due to the adsorption process of cashew leaves extract molecules on the API 5L X52 steel surface. HIGHLIGHTS Cashew (Anacardium Occidentale) leaves extract as green corrosion inhibitor is a novelty of this research Cashew leaves extract delivers up to 96 % inhibition efficiency with 500 ppm of concentration and 60 min of immersion time ElS has confirmed that cashew leaves extract inhibits the corrosion process of API 5L X52 in acidic media by boosting the impedance Cashew leaves extract contains active corrosion inhibiting agents such as polyphenol, tannin, flavonoid and alkaloid The adsorption mechanism of cashew leaves extract obeys the Langmuir isotherm GRAPHICAL ABSTRACT

Synthesis, Characterization and Electrochemical Studies on the Corrosion Inhibition Properties of Schiff Bases for Mild Steel in 1 M HCl Solution

Schiff bases (SBL1 and SBL2), non-toxic compounds were synthesized, characterized and investigated as alternative anticorrosive additives for inhibition of mild steel corrosion in I M HCl acid medium. Corrosion of the steel was monitored by Potentiodynamic Polarization (PDP), Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS) and Weight Loss (WL) techniques. The novel Schiff base ligands obtained were characterized by Ultraviolet-visible and Fourier-Transform Infrared Spectroscopy. The elemental analysis data for the Schiff base ligands were used to confirm the formula of SBL1 as C17H20N2O2 and SBL2 as C24H21N5O2. Fourier-Transform Infrared spectroscopy suggest that the formation of a complex film on the mild steel surface was due to the adsorption of SBL1 and SBL2. The adsorption process was spontaneous and consistent with the mechanism of physical adsorption as best approximated by the Langmuir adsorption isotherm. Maximum inhibition efficiency was obtained at maximum concentration of 100 ppm for both SBL1 and SBL2 with SBL2 possessing the higher inhibition efficiency (86.21%) more than SBL1 (76.92%). Effectiveness of SBL1 and SBL2 reduced with increase in time and progressed with increase in concentration of SBL1 and SBL2. PDP measurements showed that SBL1 and SBL2 acted as a mixed type inhibitor. EIS measurement reveals that the corrosion process was controlled by charge transfer process. Values of the inhibition efficacy obtained from the different techniques were comparable. SEM micrographs of mild steel surface indicated good surface protection of SBL1 and SBL2.