Studies on the metabolism of synthetic cathinones N-ethylhexedrone and buphedrone using liquid chromatography-mass spectrometry (LC-MS/MS)

N-ethylhexedrone (NEH) and buphedrone (BUPH) are synthetic drugs structurally related to natural cathinone. These synthetic cathinones are part of a large group of compounds classified as new psychoactive substances (NPS), which have caused major concern in scientific and forensic communities over the past years, due to their widespread abuse. Moreover, since NPS enter recreational markets every week, as reported by the European Monitoring Centre on Drugs and Drug Addiction (EMCDDA), there is a constant need to monitor the use/consumption of these newly synthesized substances and obtain sufficient knowledge on their metabolism and excretion profiles.

This study aims at helping to uncover the metabolic and excretion profiles of NEH and BUPH. These two synthetic cathinones, as well as selected metabolites among those expected, were synthesized, being the parent drugs used for in vivo studies. NEH and BUPH and their metabolites were quantified in 24h urines, collected from male CD-1 mice following intraperitoneal administrations (i.p., 64 mg kg-1) of NEH or BUPH (n= 3-4 mice/group). The method of analysis of cathinones and their metabolites by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was optimized and validated.

Results showed that NEH and BUPH were present in 24h mice urines at concentrations of 58.3±14.4 and 146.2±14.9 µg mL-1, respectively, and these values were in accordance with their lipophilic properties (LogP NEH = 3.6, .LogP BUPH = 2.1), which affect their bioavailability. Longer side chains are known to be associated with higher lipophilicity, which usually leads to greater drug absorption and body distribution. Metabolites resulting from the reduction of the ketone group and/or N-dealkylation of the drugs, as well as 4-aryl hydroxylation of ketone reduced NEH, were quantified in mice urine at concentrations between 1.23±0.13 and 80.3±11.4 µg mL-1. The use of these metabolites as NPS markers in the analysis of biological samples is discussed as well as their contribution to assess and estimate its consumption through wastewater samples. Future studies should comprise the identification of other metabolites, including possible phase II metabolites (glucuronides or sulfates).