Comparison of N-alkyl acridine orange dyes as fluorescence probes for the determination of cardiolipin

The phospholipid (PL), cardiolipin (CL), is found almost exclusively in the inner membrane of mitochondria and loss of CL is considered as an important indication of cell apoptosis. Previously, 10-N-nonyl acridine orange (NAO) has been used as a fluorescent probe for the visualization of CL in mitochondrial cell membranes and in solution. In this work for the determination of CL, we have synthesized two new fluorescent probes, n-tetradecyl acridine orange (C14-AO), and n-octadecyl acridine orange (C18-AO) by reacting acridine orange with the corresponding n-alkyl bromide. Using excitation and emission wavelengths at about 500 and 525 nm and varying the percentage of methanol in water as the solvent, no interaction between CL and the fluorescent probes at 75% is noted but a proportional quenching of the fluorescence signal by CL is observed at 50% or less for C14-AO and 60% or less for C18-AO. Binding efficiency of these fluorescent probes to CL is compared using dye concentrations of 5, 10, and 20 μM. C18-AO shows a better sensitivity than C14-AO and NAO, respectively, but is less selective. For C14-AO, the detection limit and limit of quantitation are 0.07 and 0.21 μM, respectively, which are better than those previously reported for NAO. One anionic PL, phosphatidic acid, shows some quenching interference to both the C14 and C18 dyes but only at concentrations above the working range for sample analysis. The CL in mitochondrial membrane samples is determined by standard addition using C14-AO. The level of CL in the outer mitochondrial membrane compared to the inner membrane is significantly increased due to the addition of cadmium chloride into the cells causing cell apoptosis.     

Rosmarinus officinalis extract as eco-friendly corrosion inhibitor for copper in 1 M nitric acid solution: Experimental and theoretical studies

Rosmarinus officinalis extract (ROE) was studied chemically (mass loss, ML), electrochemically impedance spectrometry (EIS), and potentiodynamic polarization (PDP) as a corrosion inhibitor in 1 M nitric acid. According to ML, ROE is effective like a copper preservative in 1 M HNO₃ acid solution at R.T by improving inhibitor concentration up to 77 % at 300 ppm and 25 °C. A study was conducted regarding the effect of temperature on copper adsorption, as well as the calculation of adsorption coefficients. Results indicated that physisorption increases with temperature, indicating a decrease in inhibition efficiency (%IE). Langmuir's adsorption model was consistent with the adsorption mechanism. Using the PDP method, the inhibitor accumulated on the copper surface in mixed forms. Moreover, EIS revealed that the value of double-layer capacitance dropped with an increased dose of ROE, while the charge transfer resistance improved. A different approach was taken to the examination of surfaces. Both theoretical studies and practical results were calculated and compared to demonstrate that the results were valid.     

Experimental and theoretical studies of carbon steel corrosion protection in phosphoric acid solution by expired lansoprazole and rabeprazole drugs

The effects of expired lansoprazole and rabeprazole on the corrosion protection of carbon steel in phosphoric acid (3.0 ?M) solution were examined by Tafel polarization and electrochemical impedance spectroscopy (EIS). Lansoprazole and rabeprazole concentrations (0.5, 1.0, 5.0 and 10 ?mM) in acid solution were raised, which improved corrosion prevention. Both lansoprazole and rabeprazole as the mixed inhibitors retarded the anodic and cathodic processes, as indicated by polarization data. With the increasing temperature in the range of 25–55 ?°C, the inhibition efficiency drops from 92.9% to 69.3% for lansoprazole and from 94.8% to 74.2% for rabeprazole. The major decrease in the inhibition efficiency with ascending temperature proved the physisorption of the drugs. The activation energies for carbon steel corrosion in H₃PO₄solution were enhanced from 41.6 ?kJ ?mol^?1 to 81.9 ?kJ.mol^?1and 85.9 ?kJ ?mol^?1 for lansoprazole and rabeprazole, respectively. The influence of temperature on the corrosion process of carbon steel in the acid medium was used to derive the thermodynamic quantities of corrosion. The adsorption of both lansoprazole and rabeprazole on carbon steel followed the Langmuir adsorption isotherm. The polarization data yielded outcomes that were consistent with the results arising from impedance measurements. The theoretical study of both lansoprazole and rabeprazole was done by a density functional theory (DFT) approach to realize the effects of molecular structure on their inhibitive action. Both lansoprazole and rabeprazole contain a higher E_HOMO, a lower E_LUMO and a lower energy gap than some inhibitors earlier reported as good corrosion inhibitors in the literature.     

Corrosion protection of carbon steel in acidic media by expired bupropion drug; experimental and theoretical study

The effects of expired bupropion on the corrosion protection of carbon steel in hydrochloric acid (1.0 M) and sulfuric acid (0.5 M) solutions were examined by Fourier transform infrared (FTIR) spectroscopy, Tafel polarization and electrochemical impedance spectroscopy (EIS). Bupropion concentrations in both acid solutions were raised, which improved corrosion prevention. Bupropion was a mixed inhibitor because it retarded the anodic and cathodic processes, as indicated by polarization data. The inhibition efficiency decreased with the increasing temperature from 25 to 55 °C. In the presence of bupropion, the activation energies of corrosion in both acid solutions increased. The thermodynamic quantities were deduced from the influence of temperature on the corrosion process of carbon steel in both acid media. Bupropion adsorption on carbon steel followed the Langmuir adsorption isotherm. The polarization data yielded outcomes consistent with the results arising from impedance measurements. FTIR spectroscopy showed the active sites of bupropion molecule during adsorption on the alloy surface. The theoretical study and molecular dynamics simulation of bupropion was done by a density functional theory (DFT) approach to realize the effects of molecular structure on the inhibitive action of bupropion.     

Investigation of the interaction between acridine orange and bovine serum albumin

The results from the measurement of the fluorescence spectrum showing the binding characteristics of acridine orange (AO) and bovine serum albumin (BSA) are reported. It was found that the equilibrium constant k=4848.64 l mol⁻¹, and the number of binding sites n=0.82. Based on the mechanism of the Forster energy transference, the transfer efficiency of energy and distance between the acceptor AO and BSA were found. The interaction between AO and BSA have been verified as consistent with the static quenching procedure and the quenching mechanism is related to the energy transfer.     

Experimental and theoretical studies of media effects on copper corrosion in acidic environments containing 2-amino-5-mercapto-1,3,4-thiadiazole

Corrosion behaviour of copper metal in acid solutions (HCl, H₂SO₄ and H₃PO₄) containing 2-amino-5-mercapto-1,3,4- thiadiazole (AMT) was investigated experimentally and theoretically via gravimetric, potentio-dynamic and quantum electrochemical approaches. Similar behavior was observed for H₂SO₄ and H₃PO₄ media, and related to the nature of anions at metal/solution interface. With regard to HCl, however, the rate of corrosion was determined to be low at initial stages, but high later on using an auto-catalyzing mechanism. In the presence of AMT, the experimental studies revealed that this molecule was a good anodic-type inhibitor causing substantial changes in corrosion potential. Moreover, its adsorption obeys the Langmuir isotherm. The values of ΔG _ads were determined and correlated to the inhibitor powers. Finally, the influence of media (anions) on metal corrosion was also investigated from molecular point of view by calculations of the copper-anions interaction using density functional theory.     

Corrosion inhibitory action of some plant extracts on the corrosion of mild steel in acidic media

The alcoholic extracts of eight plants namely Lycium shawii, Teucrium oliverianum, Ochradenus baccatus, Anvillea garcinii, Cassia italica, Artemisia sieberi, Carthamus tinctorius, and Tripleurospermum auriculatum grown in Saudi Arabia were studied for their corrosion inhibitive effect on mild steel in 0.5 M HCl media using the open circuit potential (OCP), Tafel plots and A.C. impedance methods. All the plant extracts inhibited the corrosion of mild steel in acidic media through adsorption and act as mixed-type inhibitors.     

Review of corrosive environments for copper and its corrosion inhibitors

This review paper deals with corrosion of copper and its alloys in corrosive environments and their corrosion inhibitors. The main corrosion inhibitor groups for copper are introduced and a review of adsorption models is provided. The main part of this work is to investigate different corrosive environments for copper and its alloys and their corrosion inhibitors used in such environments to protect copper. According to the literature, the corrosion inhibition behavior of organic corrosion inhibitors and their derivatives in comparison with inorganic ones are further evaluated. Knowing maximum corrosion inhibition efficiency of a specific corrosion inhibitor in a specific corrosive environment is helpful to choose the most appropriate corrosion inhibitor compound.     

Evaluation of Allium sativum as corrosion inhibitor for carbon steel in sulphuric acid under hydrodynamic conditions

ABSTRACT

A study on the use of Allium sativum (garlic) as corrosion inhibitor for carbon steel in 0.5?M H₂SO₄ has been carried out in static and dynamic conditions by using potentiodynamic polarization curves and electrochemical impedance spectroscopy at 0, 200, 500, 1000 and 2000?rpm. Inhibitor concentrations included 0, 100, 200, 400, 600, 800 and 1000?ppm. Under static conditions, inhibitor efficiency increases with increasing its concentration up to 400?ppm, but it decreases with a further increase in its concentration. Under dynamic conditions and short testing times, inhibitor efficiency increases with increasing the rotating speed, due to a better inhibitor transfer towards the steel surface. However, for longer testing times, inhibitor efficiency increases only during the first 2?h, and then it decreases with a further increase in time, indicating a desorption of the inhibitor molecules from the steel surface.     

Spectroscopic studies on the interaction between acridine orange and bile salts

The structure of sodium deoxycholate (NaDC) micellar aggregates has been previously reported to be helical, and two helical models have been proposed for the micellar aggregates of sodium taurodeoxycholate (NaTDC). Here we report NMR and UV-VIS studies on the interaction between acridine orange (AO) and NaDC or NaTDC aqueous micellar solutions. AO is known to aggregate in aqueous solutions. The addition of NaDC or NaTDC causes the breaking of the AO aggregates, although the binding geometry of the two bile salts with AO seems to be slightly different. The cationic dye interacts mainly with the C₁₈ and C,9 methyl groups of the bile salt molecules. This result agrees with one of the two NaTDC helical models and with some of its possible aggregates, and confirms again the helical structure attributed to the NaDC micellar aggregates within the limits of the experimental conditions tested by us.Devoted to Professor Giovannai Battista Marini Bettolo Marconi on the occasion of his 75th birthday.     

Chitosan as an eco-friendly inhibitor for copper corrosion in acidic medium: protocol and characterization

Natural biopolymer chitosan organic compound (COC) has been used as a copper corrosion inhibitor in molar hydrochloric medium. This study was conducted by weight loss, polarization curves and electrochemical impedance spectroscopy measurements. Scanning electron microscopy, energy dispersive X-ray spectrometry and atomic force microscopy studies were used to characterize the surface of uninhibited and inhibited copper specimens. The study of the temperature effect was carried out to reveal the chemical nature of adsorption. The inhibition efficiency tends to increase by increasing inhibitor concentration to reach a maximum of 87% at 10^?1 mg L^?1. The values of inhibitor efficiency estimated by different electrochemical and gravimetric methods indicate the performance of copper in HCl medium containing COC. Adsorption of COC was found to follow the Langmuir adsorption isotherm. In order to get a better understanding of the relationship between the inhibition efficiency and molecular structure of COC, quantum chemical and molecular dynamics simulation approaches were performed to get a better understanding of the relationship between the inhibition efficiency and molecular structure of chitosan.     

Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5 M H2SO4 solution

A study on the use of the methanol extract of Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5?M of sulfuric acid has been carried out by using potentiodynamic polarization curves, electrochemical impedance spectroscopy and gravimetric tests. Testing temperatures were 25°C, 40°C and 60°C. Results showed that M. sativa is a good corrosion inhibitor, with its efficiency increasing with its concentration and with time, but decreasing with the temperature. M. sativa forms a passive film on top of the steel with a passive current density and pitting potential values lower than that for uninhibited solution, and remained on the steel for 8–12?h. This film formed by iron ions and heteroatoms present in OH^? and amine groups from the extract are adsorbed on the steel and form a protective film on to the steel.     

Theoretical studies of some sulphonamides as corrosion inhibitors for mild steel in acidic medium

Density functional theory (DFT) at the B3LYP/6‐31G (d,p) and BP86/CEP‐31G* basis set levels and ab initio calculations using the RHF/6‐31G (d,p) methods were performed on four sulfonamides (namely sulfaacetamide (SAM), sulfapyridine (SPY), sulfamerazine (SMR), and sulfathiazole (STI)) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies (%IE). The order of inhibition efficiency obtained was SMR > SPY > STI > SAM which corresponded with the order of most of the calculated quantum chemical parameters namely E_HOMO (highest occupied molecular orbital energy), E_LUMO (lowest unoccupied molecular orbital energy), the energy gap (ΔE), the Mulliken charges on the C, O, N, S atoms, hardness (η), softness (S), polarizability (α), dipole moment (μ), total energy change (ΔE_T), electrophilicity (ω), electron affinity (A), ionization potential (I), the absolute electronegativity (χ), and the fraction of electrons transferred (ΔN). Quantitative structure activity relationship (QSAR) approach has been used and a correlation of the composite index of some of the quantum chemical parameters was performed to characterize the inhibition performance of the sulfonamides studied. The results showed that the %IE of the sulfonamides was closely related to some of the quantum chemical parameters but with varying degrees/order. The calculated %IE of the sulfonamides studied was found to be close to their experimental corrosion inhibition efficiencies. The experimental data obtained fits the Langmuir adsorption isotherm. The negative sign of the E_HOMO values and other thermodynamic parameters obtained indicates that the data obtained supports physical adsorption mechanism. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Extract sarampa wood (Xylocarpus Moluccensis) as an eco-friendly corrosion inhibitor for mild steel in HCl 1M

Plant extracts are currently being used as eco-friendly corrosion inhibitors. In this study, the inhibitive performance of Xylocarpus Moluccensis extract (XME) was used as an eco-friendly corrosion inhibitor for the first time. The extract was studied using electrochemical measurement on mild steel in 1M HCl. Results from FIR and phytochemical confirmed that Xylocarpus Moluccensis extract contains compound hydroxyl group, phenolic, and flavonoid content which can be used as a corrosion inhibitor. The inhibition efficiency was determined using Tafel polarization and electrochemical impedance spectroscopy and showed 68% efficiency in 500 ppm. Langmuir adsorption isotherm was used to determine the adsorption mechanism of XME. Surface characterization (AFM) was also used to study the surface morphology of protective film inhibitors.     

Spectral studies of N-nonyl acridine orange in anionic, cationic and neutral surfactants

The spectroscopic and photophysical properties of N-nonyl acridine orange – a metachromatic dye useful as a mitochondrial probe in living cells – are reported in water and microheterogeneous media: anionic sodium dodecylsulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB) and neutral octylophenylpolyoxyethylene ether (TX-100). The spectral changes of N-nonyl acridine orange were observed in the presence of varying amount of SDS, CTAB and TX-100 and indicated formation of a dye–surfactant complex. The spectral changes were also regarded to be caused by the incorporation of dye molecules to micelles. It was proved by calculated values K_b and f in the following order: K_b TX-100 > K_b CTAB > K_b SDS and f_TX-100 > f_CTAB > f_SDS. NAO binds to the micelle regardless the micellar charge. There are two types of interactions between NAO and micelles: hydrophobic and electrostatic. The hydrophobic interactions play a dominant role in binding of the dye to neutral TX-100. The unexpected fact of the binding NAO to cationic CTAB can be explained by a dominant role of hydrophobic interactions over electrostatic repulsion. Therefore, the affinity of NAO to CTAB is smaller than TX-100. Electrostatic interactions play an important role in binding of NAO to anionic micelles SDS. We observed a prolonged fluorescence lifetime after formation of the dye–surfactant complex τ_SDS > τ_TX-100 > τ_CTAB > τ_water, the dye being protected against water in this environment. TX-100 is found to stabilize the excited state of NAO which is more polar than the ground state. Spectroscopic and photophysical properties of NAO will be helpful for a better understanding of the nature of binding and distribution inside mammalian cells.     

An experimental and theoretical investigation on adsorption properties of some diphenolic Schiff bases as corrosion inhibitors at acidic solution/mild steel interface

The effect of novel synthesized three Schiff bases, namely, 1,3-bis[2-(2-hydroxy benzylidenamino) phenoxy] propane (P1), 1,3-bis[2-(5-chloro-2-hydroxybenzylidenamino) phenoxy] propane (P2), and 1,3-bis[2-(5-bromo-2-hydroxybenzylidenamino) phenoxy] propane (P3), on the corrosion of mild steel in 0.1 M HCl was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy methods. Polarization measurements suggest that P1 acts as mixed type inhibitor while P2 and P3 behave as mainly cathodic inhibitors for acidic corrosion of steel. All electrochemical measurements show that inhibition efficiencies increase with increase in inhibitor concentration. This reveals that inhibitive actions of inhibitors were mainly due to adsorption on steel surface. Adsorption of these inhibitors follows Temkin adsorption isotherm. The correlation between the adsorption ability of inhibitors and their molecular structures has been investigated using quantum chemical parameters obtained by MNDO semi-empirical method. Calculated quantum chemical parameters indicate that Schiff bases adsorbed on steel surface by chemical mechanism.     

Use of an amide-type corrosion inhibitor synthesized from the coffee bagasse oil on the corrosion of Cu in NaCl

An amide, namely N-[2-[(2-hydroxyethyl) amino] ethyl]-amide, extracted from the fatty acids contained in the coffee bagasse, has been investigated as a possible green corrosion inhibitor for copper in 3.5% NaCl by using potentiodynamic polarization curves and electrochemical impedance spectroscopy measurements. Results were complemented by detailed scanning electronic microscopy, FTIR and gas chromatography studies. Results have shown that N-[2-[(2-hydroxyethyl) amino] ethyl]-amide is a good, mixed type of corrosion inhibitor, with an efficiency that increases with its concentration but it decreases with a rise in the temperature. It adsorbs chemically onto the copper surface by following a Langmuir type of adsorption isotherm.     

Correlation between the molecular structure and the corrosion inhibition efficiency of chestnut tannin in acidic solutions

The frontier orbital theory and the inhibitor adsorption theory were applied to the results of the quantum calculations and corrosion rate measurements, respectively, in order to elucidate the chestnut tannin inhibitory action on low-carbon steel corrosion in 2 M HCl. Nine major constituents of chestnut tannin—vescalagin, castalagin, vescalin, castalin, gallic acid, ellagic acid, mono-, di- and trigalloylglucose—were modeled by molecular mechanics, molecular dynamics and semiempirical quantum NDDO method with PM3 parametrization. The geometrical structure, the energy of the highest occupied (HOMO) and lowest unoccupied molecular orbital (LUMO), the HOMO–LUMO energy gap, the distribution of the HOMO electron density and the magnitude and direction of the dipole moment were calculated for each molecule. Molecular reactivity that is related to its adsorbability by the HSAB principle, was studied by calculating the absolute electronegativity, absolute hardness and the electron donating ability. The quantum calculations results, coupled with those derived from the adsorption theory, gave a consistent picture of the investigated corrosion system.     

Olive leaf extract as a green corrosion inhibitor of reinforced concrete contaminated with seawater

In reinforced concrete, a high alkaline medium, steel is commonly protected by formation a passive oxide film. Nevertheless, contamination with chlorides or carbonation causes the deterioration of protective film and the initiation of pitting corrosion. Hence, the need to enrich the fresh concrete solution with a good corrosion inhibitor. In accordance with green chemistry to evade toxicity and minimize waste, we have chosen to replace the usual inhibitors with an alternative not only ecological but also derived from biological wastes, in a perspective of circular economy emphasizing that waste can offer important compounds at an affordable price and easily available. In this context this work seeks to valorize the dried olive leaves extract as an inhibitor in alkaline chloride solution (pH 13). The targeted plant was grown in arid zones of Saudi Arabia and their leaves are usually disposed of as solid waste or animal feed. Four extraction solvents of different polarities were used; methanol, ethyl acetate, dichloromethane and hexane. The anticorrosive activity was performed using different electrochemical techniques; polarization curves, electrochemical impedance spectroscopy and Mott-Schottky analyses. The polarization studies proved that extract from olive leaves is a mixed type inhibitor in a solution of NaOH (0.1 M) + NaCl (0.5 M),with a predominant anodic effectiveness. The best inhibition of 91.9% is provided with methanol extract. GC–MS analysis showed the presence of compounds containing the heteroatoms N and O with the π electrons which are responsible for the corrosion inhibition activity. The olive leaves have been found to be high in phenol and flavonoid content. Inhibition efficiency of the olive leaves extracts increases with the polarity of extraction solvents but also it appears that it depends on another factors.     

Synthesis,biological evaluation and computational studies of fused acridine containing 1,2,4-triazole derivatives as anticancer agents

A novel series of fused acridine containing 1,2,4-triazole derivatives (13a-j) have been synthesized and their structures were confirmed by ¹HNMR, 13CNMR and mass spectral data. Further, all these derivatives were tested for their anticancer activity against four human cancer cell lines A549 (Lung), MCF7 (Breast), A375 (Melanoma) and HT-29 (Colon). The IC₅₀ values range of target compounds shown 0.11 ± 0.02 to 13.8 ± 0.99 µM as compared with standard drug range 0.11 ± 0.02 to 0.93 ± 0.056 µM. Among them, compounds 13d, 13f, 13g, 13h, 13i, and 13j were exhibited more potent activity. Docking simulation was performed as a trial to study the mechanisms and binding modes of these compounds towards the DNA target. The results showed these compounds have intercalated placement in the active sites and stable interactions similar to the co-crystallized reference ligand. Further, these compounds (13a-j) were investigated for Drug-likeness, ADME properties and Toxicity risk assessment.