Oxidation Of Morin Research Articles

Electrocatalytic Oxidation and Determination of Morin at a Poly(2,5-dimercapto-1,3,4-thiadiazole) Modified Carbon Fiber Paper Electrode

Voltammetric determination of morin on carbon fiber paper (CFP) electrode modified by electropolymerization of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) in phosphate buffer solution (PB, pH 9.0) have been studied. This modified electrode showed strong electrocatalytic activity toward the oxidation of morin, a flavonoid at physiological pH (PB, pH 7.0). Morin gave a sensitive anodic peak at 0.245 V (vs. SCE). The parameters influencing the anodic peak of morin such as effect of pH, effect of scan rate and concentration have been optimized. The electrochemical process was found to be irreversible and adsorption-controlled. Under the optimum conditions, the anodic peak current was linear to concentration of morin in the range of 2.5 × 10−10–2.75 × 10−9 M and detection limit was found to be 8.3 × 10−11 M. The practical application of the modified electrode was successfully demonstrated for the determination of morin in mulberry leaves.

Determination of pentahydroxyflavones using coated chitosan multi-wall carbon nanotubes and an ionic liquid glassy carbon electrode by adsorption stripping voltammetry (AdSV)

Abstract In this work, the determination of pentahydroxyflavones on a glassy carbon electrode modified with chitosan and multi-walled carbon nanotubes (Ch–MWCNT) was studied. The presence of ionic liquids (LIs) on the surface of the modified electrode (Ch–MWCNT–LI–GCE) increased the oxidation current by nearly 20%. The pH and electrochemical parameters (adsorptive potential and time accumulation) were optimized based on the oxidation of morin to obtain the following values: pH, 3.2; E ads , − 0.10 V; and t ads , 70 s. The detection limit was 0.54 × 10 − 7 mol L − 1 and the RSD was 1.7%. The new method was used to quantify pentahydroxyflavones in plant tissue samples.

Synthesis of narrowly dispersed silver and gold nanoparticles and their catalytic evaluation for morin oxidation

We present a study on the synthesis of narrowly dispersed silver and gold nanoparticles using generation five amino-terminated poly(amidoamine) dendrimers as a template. UV–vis spectrophotometry was performed to monitor the synthesis process and to characterize the metal nanoparticles. Infrared (IR) spectroscopy, and transmission electron microscopy (TEM) were also used to characterize the metal nanoparticles. A catalytic oxidation of morin (quercetin) in the presence of hydrogen peroxide was performed as a model reaction to evaluate the metal nanoparticle activities. Ultra high performance liquid chromatography analysis was performed to identify the reaction products. The kinetic data obtained were modeled to the Langmuir–Hinshelwood equation. The encapsulated silver and gold nanoparticles show high activity which confirm the passive interaction with the dendrimer.

The preparation of well-defined dendrimer-encapsulated palladium and platinum nanoparticles and their catalytic evaluation in the oxidation of morin

The preparation of dendrimer-encapsulated platinum (Pt-DENs) and palladium (Pd-DENs) nanoparticles using generation 6-hydroxyl-terminated poly(amidoamine) (PAMAM) dendrimers as a templating agent is described. These nanoparticles were characterized using UV–vis spectrophotometry, spectrofluorophotometry, Fourier transform infrared spectrometry (FTIR), and high resolution transmission electron microscopy (HRTEM). The UV–vis spectra of palladium and platinum dendrimer-encapsulated nanoparticles gave a clear proof that nanoparticles were formed. It was found from FTIR spectra that there are shifts of peaks from higher wave numbers to lower wave numbers after reduction with sodium borohydride and these confirm the encapsulation of nanoparticles inside the voids of the dendrimer. The particle diameters were found to be 1.4±0.2 and 1.6±0.2nm in diameter for palladium and platinum respectively from HRTEM. These nanoparticles were evaluated as catalysts in the oxidation of morin by hydrogen peroxide. The kinetic data was modeled to the Langmuir–Hinshelwood equation. The model allows relating apparent rate constant to the total surface area (S) of the nanoparticle. The Langmuir–Hinshelwood model also allows a direct relationship between the kinetic constant (k) and Kmorin and KH2O2. The Arrhenius and Eyring equations were used to determine thermodynamic parameters for the oxidation of morin.

Electrooxidation of morin hydrate at a Pt electrode studied by cyclic voltammetry

The process and the kinetics of the electrochemical oxidation of morin in an anhydrous electrolyte have been investigated using cyclic and differential pulse voltammetry. The oxidation mechanism proceeds in sequential steps related to the hydroxyl groups in the three aromatic rings. The oxidation of the 2′,4′dihydroxy moiety at the B ring of morin occurs first, at very low positive potentials, and is a one-electron, one-proton irreversible reaction. The rate constant, electron transfer coefficient and diffusion coefficients involved in the electrochemical oxidation of morin were determined. The influence of the deprotonation of the ring B hydroxyl moiety is related to the electron/proton donating capacity of morin and to its radical scavenging antioxidant activity.

Oxidation of an organic dye catalyzed by MnOx nanoparticles

We present a study on the catalytic oxidation of the organic dye morin by hydrogen peroxide in the presence of manganese oxide nanoparticles in aqueous solution. The ultrathin manganese oxide nanoparticles consist of c*-disordered potassium birnessite and are immobilized on spherical polyelectrolyte brushes. The catalytic activity of these composite particles was investigated using the oxidation of morin by hydrogen peroxide as a model reaction. The oxidative degradation of morin was followed by UV/vis spectroscopy leading to an apparent rate constant kapp. We propose a modeling of the results in terms of a Langmuir–Hinshelwood model. kapp can be related to the kinetic constant k and to the apparent adsorption constants of H2O2 and morin. Based on this model, the dependence of kapp on temperature can be traced back to the activation energy of the rate constant k and the adsorption enthalpies of both educts on the surface of the nanoparticles.

Online Coupling of Lab-on-Valve Format to Amperometry Based on Polyvinylpyrrolidone-Doped Carbon Paste Electrode and Its Application to the Analysis of Morin.

The potential capabilities and analytical performance of lab-on-valve (LOV) manifold as a front end to amperometry have been explored for the on-line determination of morin. Meanwhile, the electrochemical behaviors of morin were investigated based on polyvinylpyrrolidone- (PVP-) doped carbon paste electrode (CPE), which found that PVP can significantly improve its oxidation peak current. The excellent amperometric current response was achieved when the potential difference (ΔE) of 0.6 V was implemented in pH 6.5 phosphate buffer solution (PBS) that served as the supporting electrolyte. A well-defined oxidation peak has been obtained in studies using PVP as a modifier of CPE based on the oxidation of morin. The present work introduces the LOV technique as a useful tool for amperometric measurement, documents advantages of using programmable flow, and outlines means for miniaturization of assays on the basis of PVP modified CPE. The proposed method was applied successfully to the determination of morin in real samples, and the spiked recoveries were satisfactory.

Electrochemical oxidation of morin and interaction with DNA

A poly (tetrafluroethylene)-deoxyribonucleate acid (PTFE-DNA) film-modified glassy carbon electrode (GCE) has been fabricated. The electrochemical oxidation behaviors of morin as well as its interaction with DNA have been studied at PTFE-DNA film-modified GCE and bare GCE by electrochemical methods. This modified electrode shows an enhanced effectiveness towards the oxidation of morin. Importantly, as to the interaction between morin and DNA in solution, characteristic parameters such as the binding stoichiometry and association equilibrium constant according to the Hill model for cooperative binding have been determined on the basis of linear sweep voltammetry and chronocoulometry.

Solid State Electrochemical Oxidation Mechanisms Of Morin in Aqueous Media

The mechanism of electrochemical oxidation of morin has been studied using cyclic, differential pulse and square-wave voltammetry techniques in aqueous electrolyte with solid, insoluble morin hydrate mechanically transferred to a glassy carbon electrode surface, over a wide pH range. The oxidation mechanism proceeds in sequential steps, related with the hydroxyl groups in the three aromatic rings and the oxidation is pH dependent over part of the pH range the oxidation potentials are shifted to lower values with increasing pH. Oxidation of the 2′,4′dihydroxy moiety at the B ring of morin occurs first, at very low positive potentials, and is a one electron one proton reversible reaction. The hydroxyl groups oxidized at more positive potentials were shown to undergo an irreversible oxidation reaction.

Kinetic-fluorimetric study of the activator effect of zirconium(IV) on the air oxidation of morin catalysed by manganese(II)

A kinetic study of the activator effect of zirconium(IV) on the manganese(II)-catalysed air oxidation of morin has been made. The effect of ammonia, ethanol, morin, manganese(II) and zirconium(IV) concentrations and of temperature was examined in order to obtain the optimum conditions for the determination of zirconium(IV) and to establish the kinetic dependence of each of these variables for the catalysed and activated reactions. The reaction was followed by measuring the decrease in fluorescence at 548 nm, with an excitation wavelength of 417 nm. A kinetic-fluorimetric method for the determination of zirconium(IV) is proposed. The calibration graphs were obtained by applying the fixed time, fixed concentration, initial rate and rate constant methods. The method is linear up to 250 ng ml–1 of zirconium(IV). The precision was calculated for the different methods applied and was always smaller than 3%. The main interferences were due to BeII, CuII and MgII. Moreover, the zirconium(IV)'s activator effect has been used to improve the kinetic-fluorimetric determination of manganese(II). The method is linear up to 60 ng ml–1, with a detection limit of 0.26 ng ml–1 for manganese(II), and a sensitivity enhancement of about 50% is obtained in the presence of the activator.

Kinetic-fluorimetric study of the catalytic effect of manganese(II) on the air oxidation of morin

A kinetic study of the air oxidation of morin catalysed by trace amounts of manganese(II) has been made. The effect of ammonia, ethanol, morin and manganese(II) concentrations was examined, and the partial orders with respect to these reagents and the kinetic constants were obtained. The catalysed reaction is of zero order with respect to morin (for the range 1.48 × 10–5–2.07 × 10–5M), 0.75 order with respect to ammonia (between 0.40 and 6.68 M) and first order with respect to manganese(II). The effect of temperature was also studied. The activation energy was calculated by applying the Arrhenius equation (linear between 20 and 40 °C). The reaction was followed by measuring the decrease in fluorescence at 548 nm, with an excitation wavelength of 415 nm. A kinetic-fluorimetric method for the determination of trace amounts of manganese(II) is proposed. Calibration graphs were obtained by applying the fixed time, fixed concentration, initial rate and rate constant methods. The method is linear up to 70 ng ml–1 of manganese(II); the detection and quantitation limits were found to be 0.54 and 1.81 ng ml–1, respectively. The precision was calculated for the different methods applied, and varies between 1.9%(initial rate) and 4.5%(fixed time at 5 min). BeII, CuII and ZrIV increase the catalysed reaction rate, and MgII, CrIII and FeIII decrease the reaction rate.

Kinetic-fluorimetric determination of copper(II), based on its catalytic effect on the oxidation of morin with hydrogen peroxide

A kinetic method is described for the determination of trace amounts of copper(II) based on its catalytic effect on the oxidation of 3,5,7,2′,4′-pentahydroxyflavone (morin) by hydrogen peroxide. The reaction is followed by measuring the rate of decrease in fluorescence (λex.= 463 nm, λem.= 548 nm). The optimum conditions are as follows: pH 10.5 (ammonium chloride-ammonia buffer), 0.005% morin, 20% ethanol, 0.9% hydrogen peroxide and 25 °C. The calibration is linear for concentrations up to 50 ng ml–1 with a precision of 1.7% and the detection limit is 0.4 ng ml–1 of Cu(II). The main interferences are due to Be(II), Mn(II), Zr(IV), Fe(III) and Mn(VII).In the absence of H2O2, higher amounts of Cu(II) catalyse the air oxidation of morin. In this instance, the calibration graph is linear between 150 and 500 ng ml–1.