pH and Temperature Responsive Electrooxidation of Thiazole Derivatives and Preliminary Screening of Their Antioxidant Activity

Abstract

Thiazole and its derivatives have extensive pharmacological, industrial and biological applications. In the present work an attempt has been made to evaluate important physico-chemical parameters of two thiazole derivatives, 2-amino-5-nitrothiazole (ANT) and 2-amino-3-thioxothiazolidin-4-one (ATO) for proposing their redox mechanism using cyclic, square wave and differential pulse voltammetric techniques. Differential pulse voltammetry was conducted in media of different pH for the determination of acid base dissociation constant (pKa) and number of electrons and protons involved in proton coupled electron transfer processes. Cyclic voltammetry was employed for getting general voltammetric portrait of the compounds and evaluation of kinetic parameters like diffusion coefficient and heterogeneous electron transfer rate constant. Square wave voltammetry was performed for ensuring the reversible or irreversible nature of the redox reactions of the analytes. The feasibility of the redox reactions were estimated by computing the thermodynamic parameters by observing the effect of temperature on the anodic response of the compounds. Computational studies were carried out and the theoretical findings were found in line with the experimental results. Moreover, the compounds were screened for cytotoxicity and antioxidant activity.

pH and Temperature Responsive Electrooxidation and Antioxidant Activity of Indole-3-Carbaldehyde

“…4. 40 The k e values (Table I) of the order of 10 −6 and 10 −5 support the irreversible nature 41,42 of the oxidation of I3C. The temperature dependent increase in rate constant can be related to the faster diffusion due to possible decrease in number of attached solvent molecules (solvation number) around the electroactive moiety of the analyte.…”

“…The temperature dependent change in peak position toward lower potential values accompanied with increase in current intensity points to facile oxidation and faster mobility of the analyte due to possible decrease in solvation number of the analyte and viscosity of the medium at higher temperature values. 40 From the CVs obtained at different temperatures, the D values listed in Table I were evaluated. The increase in magnitude of D e from 6.96 × 10 −7 to 1.84 × 10 −6 cm 2 /s with rise in temperature from 308 to 328 K can be related to the increase in thermal energy of I3C due to decrease in both viscosity of the solvent and hydrodynamic radius of the analyte according to Stokes-Einstein relation (D = k b T/6πηr).…”

Cyclic Voltammetric Behaviour and High-Performance Liquid Chromatography Amperometric Determination of Levamisole

“…The protonated form of levamisole (iv), predominating at low pH values (pKa = 7), can be oxidised via two-electron, one-proton oxidation (vi). This initial oxidation reaction results in the formation of free radicals (v); which could lead to the possible formation of a dimer, as is commonly reported in a number of studies undertaken on related compounds [37][38][39][40]. Masui et al [36] have studied the voltammetric oxidation of a number of different amines.…”

“…Figure 3 presents the overall mechanism we propose for electrochemical oxidation, reported here for levamisole. Amjad et al [37] studied the voltammetric behaviour of a number of compounds that are structurally related to levamisole, showing the voltammetric one-proton, two-electron oxidation of 2-amino-5-nitrothiazole. The protonated form of levamisole (iv), predominating at low pH values (pKa = 7), can be oxidised via two-electron, one-proton oxidation (vi).…”