Elucidation of the Phase I and Phase II metabolic pathways of (±)-4′-methylmethcathinone (4-MMC) and (±)-4′-(trifluoromethyl)methcathinone (4-TFMMC) in rat liver hepatocytes using LC–MS and LC–MS2

(±)-4′-Methylmethcathinone hydrochloride [(±)-mephedrone, 4-MMC] is a synthetic “legal high”, with a classical cathinone structure similar to methcathinone. In this study, the in vitro metabolism of 4-MMC was investigated in Sprague-Dawley rat hepatocytes to characterise the associated Phase I and II metabolites. 4-MMC was incubated with rat liver hepatocytes, and the reaction mixture was analysed on a zwitterionic hydrophilic interaction (ZIC®-HILIC) column using LC–MS and LC–MS2. 4-MMC was metabolised, yielding 17 metabolites. These metabolites were structurally characterised on the basis of accurate mass analyses and LC–MS2 fragmentation patterns and the major metabolic routes for 4-MMC determined to be via (i) oxidation of the 4′-methyl group and (ii) reduction of the β-keto moiety. The biotransformation of a modified 4′-trifluoromethyl- derivative (4-TFMMC) has also been studied and shows significant differences in its metabolism compared to 4-MMC. Key pharmacokinetic parameters for both drugs have been calculated [biological half-lives (t½) for 4-MMC = 61.9 min and for 4-TFMMC = 203.8 min] and this data may aid in the understanding of in vivo metabolism and the likely pharmacokinetic effects of chemical/structural modifications within this class of controlled substances

Graphical abstractThe prevalence of cathinone-derived “legal highs” on the recreational drug market has given rise to a number of legal, analytical and clinical challenges. A full elucidation of the biotransformational pathways of (±)-mephedrone (4-MMC) and the bioisosteric derivative, 4-TFMMC, using LC–MS and LC–MS2, with key pharmacokinetic data is presented.Figure optionsDownload full-size imageDownload as PowerPoint slide