Application of liquid-phase microextration to the analysis of some antimalarial drugs and their metabolites in plasma

Author(s)

Igor Rafael dos Santos Magalhães

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2009-09-23

Examining board members

Pierina Sueli Bonato; Vera Lucia Lanchote; Regina Lucia de Moraes Moreau; Regina Vincenzi Oliveira; Ana Valéria Colnaghi Simionato

• Advisor: Pierina Sueli Bonato

Abstract

Currently, malaria is the main parasitic infection and shows worldwide distribution. Among therapeutic options used, chloroquine (CQ), mefloquine (MQ) and, more recently, artemether (ART) have been standing out. According to the literature, pharmacokinetic studies of these drugs have been hampered by the lack of proper methods of analysis in biological fluids and, regarding the chiral drugs (CQ and MQ), with the ability to determine the individual enantiomers. Therefore, the aim of this work was to evaluate the utilization of liquid-phase microextraction as the sample preparation technique for the determination of these antimalarial drugs and their metabolites in plasma. The enantioselective analysis of CQ and its metabolites was carried out using LPME as technique of sample preparation, which yielded recovery rates within 28- 66%. These analytes were resolved on a Chirobiotic V column in the polarorganic mode and further detected using mass spectrometry (MS) with electrospray interface (ESI) in the positive mode. The developed method was linear in the range of 5-500 ng mL-1 for all analytes studied. The kinetic disposition of CQ and its main metabolite monodesethylchloroquine (DCQ) in rats suggests enantioselectivity following the administration of the racemic drug, with higher concentrations of (+)-(S)-CQ and (-)-(R)-DCQ. The method for the analysis of the enantiomers of MQ and its achiral metabolite carboxymefloquine (CMQ) also had LPME as technique of sample preparation. The extraction of these analytes was carried out in two-steps to obtain efficient recovery rates (values within 35-38%). The analytes were resolved on a Chirobiotic T column in polar-organic mode and ultraviolet detection was performed at 285 nm. The method was linear in the range of 50-1500 and 50-3000 ng mL-1 for the enantiomers of MQ and CMQ, respectively. The kinetic disposition of MQ in rats indicates enantioselectivity with higher concentrations of (+)-(RS)-MQ following the administration of the racemic drug. The chromatographic resolution of ART and its metabolite dihydroartemisinin (DHA) in the reversed mode was achieved utilizing a column containing Si-Zr-PMTDS as stationary phase and their detection was conducted employing MS in the positive ESI mode. The optimized two-phase LPME procedure for the extraction of ART and DHA from plasma showed recovery values of 32 and 25%, respectively. The developed method was linear over the range of 5-1000 ng mL-1 for both analytes. The pilot study of kinetic disposition in rats showed higher concentrations of DHA. The obtained results confirm the feasibility of LPME for the extraction of these antimalarial drugs and their metabolites from plasma. (AU)