Detection of Metabolites of the New Synthetic Cannabinoid MDMB-4en-PINACA in Human Urine by Liquid and Gas Chromato-Mass Spectrometry Methods

MDMB-4en-PINACA belongs to the new synthetic psychoactive compounds that have been distributed in Russia since at least 2020 and is highly active against the human cannabinoid receptor CB1. Its distinctive feature is the presence of an N-pentene residue, which is rare for this group of compounds. The significant hydrophobicity of MDMB-4en-PINACA, like most other synthetic cannabimimetics on the world market, results in almost complete biotransformation of the parent compound and very low levels in urine. Hence the need to identify its metabolites, the detection of which would indicate the use of MDMB-4en-PINACA. To solve this problem we used gas and liquid chromatography-mass spectrometry methods, including high-performance chromatography-mass spectrometry with a quadrupole time-of-flight detector and a three-dimensional ion trap detector equipped with an electrospray ionization source. A number of putative metabolites of MDMB-4en-PINACA in human urine were identified as products of hydrolysis, mono- and dihydroxylation, reduction, dihydrodiol formation, carboxylation, carboxylation with elimination of methylene group, N-dealkylation and combinations of these processes. A number of metabolites were found in the form of glucuronides. The obtained results are in good agreement with literature data. For routine chemical-toxicological and forensic chemical analysis of urine by gas chromatography-mass spectrometry is optimal to search for products of hydrolysis, dihydroxylation and dihydrodiol formation, while when using liquid chromatography-mass spectrometry is also recommended detection of glucuronides of hydrolysis products and dihydrodiol formation.