Electroanalytical method for the analysis of methyldopa in pharmaceutical tablets using a crude extract of laccase from Pycnoporus sanguineus as oxidizing agent

Abstract

Several colorimetric and chromatographic methods have been used for the identification and quantification of methyldopa (MA) in pharmaceutical formulations and clinical samples. However, these methods are time- and reagent-consuming, which stimulated our efforts to develop a simple, fast, and lowcost alternative method. We carried out an electroanalytical method for the determination of MA in pharmaceutical formulations using the crude enzymatic extract of laccase from Pycnoporus sanguineus as oxidizing agent. This method is based on the biochemical oxidation of MA by laccase (LAC), both in solution, followed by electrochemical reduction on glassy carbon electrode surface. This method was employed for the determination of MA in pure and pharmaceutical formulations and compared with the results obtained using the official method. A wide linear curve from 2.5 x 10^-5 to 1 x 10-4 mol L^-1 was found with a detection limit calculated from 4.5 x 10^-6 mol L^-1.