Metabolic Profile of Four Selected Cathinones in Microsome Incubations: Identification of Phase I and II Metabolites by Liquid Chromatography High Resolution Mass Spectrometry.

Alexandra M. M. Antunes,Beatriz T. Lopes,Maria João Caldeira,Helena Gaspar

doi:10.3389/fchem.2020.609251

Abstract

Consumption of synthetic cathinones, the second largest class of new psychoactive substances (NPS) reported worldwide, represents a serious public health risk. One of the biggest challenges created by the rapid spread of NPS on the illegal drug market is the discovery of selective biomarkers for their detection in biological matrices, which is only possible through the study of their metabolic profile. The synthetic cathinones 4′-methyl-N,N-dimethylcathinone (4-MDMC), 4′-methyl-N,N-diethylcathinone (4-MDEC), 4′-chloro-α-pyrrolidinovalerophenone (4Cl-PVP), and 4′-chloroethylcathinone (4-CEC) are NPS recently seized in Europe, and, with the exception of 4-CEC, no metabolism study was reported for these cathinones. With the ultimate goal of overcoming this gap, these cathinones were incubated in vitro in human and rat liver microsomes in the presence of Phase I and II (glucuronidation) co-factors, using α-pyrrolidinovalerophenone (α-PVP) as positive control. The metabolite identification was performed by liquid chromatography coupled to tandem high resolution mass spectrometry (LC-HRMS/MS). This allowed the identification of multiple Phase I and glucuronide metabolites of the selected cathinones. Additionally, a new glucuronide conjugate, derived from the recreational drug α-PVP, was herein identified for the first time. Importantly, we have demonstrated that 4-MDMC and 4-MDEC can act as prodrugs of the controlled substances 4-MMC and 4-MEC, respectively. The metabolites herein identified are expected to play an important role not only by acting as potential selective biomarkers of the intake of the synthetic cathinones selected for this study but also to understand their potential adverse effects and link these causative agents to toxicities, thereby helping in the treatment of non-fatal intoxications.

Highlights

new psychoactive substances (NPS) are a range of substances, mostly synthetic, that have been emerging in the recreational drugs market with the purpose of mimicking the effects of classic drugs and circumvent legislation restrictions against illicit substances (German et al, 2014)
The analytical standards of the hydrochloride salts of the selected cathinones used in this work were previously obtained and characterized within the scope of the protocol established between the Faculty of Sciences of the University of Lisbon (FCUL) and the Forensic Science Laboratory from Portuguese Criminal Police (LPC-PJ): 4-MDMC, 4-MDEC and α-PVP were synthesized at FCUL, as described by Gaspar et al (2018), while 4Cl-PVP and 4-CEC were obtained from seized samples provided by LPC-PJ (Antunes et al, 2020)
Taking into consideration that liver microsome incubations were already successfully used for the generation of metabolites that occur in vivo for other cathinones (Meyer and Maurer, 2010; Meyer et al, 2010, 2012; Strano-Rossi et al, 2010; Negreira et al, 2015), this in vitro model was used for the identification of the metabolite profile of the four para-substituted cathinones, 4-MDMC, 4-MDEC, 4Cl-PVP, and 4-CEC, selected for this study

Summary

Introduction

NPS are a range of substances, mostly synthetic, that have been emerging in the recreational drugs market with the purpose of mimicking the effects of classic drugs and circumvent legislation restrictions against illicit substances (German et al, 2014). The term NPS, according to the Directive (EU) 2017/2103 (EU, 2017) designates substances that are not covered by the Single Convention on Narcotic Drugs of 1961 neither by the Convention on Psychotropic Substances of 1971 but are likely to present health or social risks comparable to that posed by substances listed in those conventions. The second largest group of NPS reported worldwide (UNODC, 2018; EMCDDA, 2020) are βketo phenethylamines, structural analogs of cathinone, the major psychoactive alkaloid present in the leaves of Catha edulis. This plant, usually known as khat, is native from eastern Africa and southern Arabia, where it has been used, over centuries, due to its stimulant effects (Valente et al, 2014; Pieprzyca et al, 2020). Synthetic cathinones are known to produce psychostimulant effects similar to methamphetamine, cocaine, or MDMA (ecstasy) by interacting with the plasma membrane transporters of the monoamine neurotransmitters, dopamine, norepinephrine, and serotonin, increasing their synaptic cleft concentration (German et al, 2014; Weinstein et al, 2017)

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