Mass spectrometric characterization and identification of new methcathinone metabolites in human blood (plasma), urine and hair by liquid chromatography-high field quadrupole exactive orbitrap mass spectrometer

•Methcathinone profiles were meticulously investigated by LC-Q Exactive HF MS.•Fifteen unreported metabolites were tentatively characterized and identified.•Five new metabolic pathways were reported.•It is the first report on the metabolic profiles of methcathinone in human hair.•Metabolic differences in urine, blood and hair samples were compared. Methcathinone metabolic profiles were meticulously evaluated in human blood (plasma), urine and hair samples. Ultrasound-assisted extraction with methanol was used to hair extraction, while solid-phase extraction (SPE) was applied to urine and blood (plasma) samples. Liquid chromatography-high field quadrupole exactive orbitrap mass spectrometer (LC-Q Exactive HF MS) was then applied to analyze the extracts. Full-scan positive-ion mode and the targeted MS/MS strategies were firstly employed to obtain precise mass measurements. Seventeen metabolites, including 14 phase I and 3 phase II metabolites, were characterized and preliminarily identified. In addition to methcathinone and cathinone, 15 unreported metabolites were identified initially. Six metabolic pathways, including demethylation, ketone reduction, glucuronidation, hydroxylation, acetylation and sulphation were also illuminated in this work, containing five novel metabolic pathways of methcathinone. Although methcathinone and cathinone are widely considered to be the primary biomarker, they were not detected in blood (plasma) samples. By comparing the contents and metabolic time points of these metabolites in different biological samples, it was determined that urine samples can serve as the preferred biological material for identifying methcathinone misuse. M4 (Demethylation + monohydroxlyation) was detected in all the biological samples, suggesting that it can potentially act as a new biomarker for monitoring methcathinone abuse.