Development of a New Method for the Quantitation of Metabolites in the Absence of Chemically Synthetized Authentic Standards

Publication date: Available online 21 February 2019Source: Journal of Pharmaceutical and Biomedical AnalysisAuthor(s): Altares R., F.M. Márquez del Pino, Benedit G., M.J. Guillén, Cuevas C., M.A. Pérez de la Cruz, Aviles P.AbstractA new method for the quantification of metabolites in the absence of a chemically synthetized authentic standard is described herein. Metabolites to be used as reference standards were obtained biologically from microsomes incubation. The method is a stepwise process in which, only the radiolabeled (14C) and non-radiolabeled parent compound are required. Briefly, the separation and principles of equimolar detection of LC-radioactivity were applied and, a calibration curve of the 14C-parent compound was used to quantify the formation of its 14C-metabolite. In turn, serial dilutions of this 14C-metabolite were the base for the calibration curve that allowed the quantification of the non-radiolabeled metabolite.This method was applied in plasma samples obtained from a dog pharmacokinetic study in which, a PharmaMar compound (lurbinectedin) and its N-desmethylated metabolite were quantified and, the results compared to those obtained by the classical approach (with the chemically synthetized N-desmethylated metabolite). Plasma concentrations obtained with the two methods were very similar, with standard relative errors between -11% to -4%. Similar, main pharmacokinetic parameters were calculated with the concentrations obtained either thru this metho...
Source: Journal of Pharmaceutical and Biomedical Analysis - Category: Drugs & Pharmacology Source Type: research