Influence of methanol, ethanol and cypermethrin on the Glutathione S-tranferase catalyzed reaction of Glutathione with 1-chloro-2,4-dinitrobenzene: A method for detection and quantification of cypermethrin

This article describes application of normal mediatorless cyclic voltammetry and UV-visible spectroscopy to study the Glutathione S-tranferase (GST) catalyzed reaction of reduced glutathione(GSH) with 1-chloro-2,4-dinitrobenzene(CDNB) in two solvents methanol and ethanol, and influence of pyrethroid cypermethrin on it. The course of the reaction between CDNB and GSH in presence of GST differs in the two solvents, viz., methanol and ethanol. Unlike the case when ethanol was used as the solvent, in methanol GSH got transformed to an electro active state under the influence of electrode polarization. This electro active intermediate undergoes oxidation at 0.3 V, sufficiently stable (more than two hours) and reacts with CDNB to form UV active but electro inactive final product. The same electro active intermediate is also formed by non-electrochemical process in presence of CDNB in methanol and the formation is catalyzed by GST. The said reaction is quantitatively affected by cypemethrin. A 25 ppb cypermethrin solution can suppress completely the cyclic voltammetric peak as well as the UVpeak obtained from a 1:1 millimolar mixture of GSH and CDNB in presence of 20 μL (0.02 mg) of GST. Based on this, an electrochemical method for quantification of cypermethrin has been proposed that can detect cypermethrin down to 2 ppb.The work has opened up new possibilities for electrochemical study of detoxification processes carried out by GSH.