Low resolution and high resolution MS for studies on the metabolism and toxicological detection of the new psychoactive substance methoxypiperamide (MeOP)

Abstract

In 2013, the new psychoactive substance methoxypiperamide (MeOP) was first reported to the European Monitoring Centre for Drug and Drug Addiction. Its structural similarity to already controlled piperazine designer drugs might have contributed to the decision to offer MeOP for online purchase. The aims of this work were to identify the phase I/II metabolites of MeOP in rat urine and the human cytochrome P450 (CYP) isoenzymes responsible for the initial metabolic steps. Finally, the detectability of MeOP in rat urine by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography coupled with multistage mass spectrometry (LC-MS(n)) standard urine screening approaches (SUSAs) was evaluated. After sample preparation by cleavage of conjugates followed by extraction for elucidating phase I metabolites, the analytes were separated and identified by GC-MS as well as liquid chromatography-high resolution-tandem mass spectrometry (LC-HR-MS/MS). For detection of phase II metabolites, the analytes were separated and identified after urine precipitation followed by LC-HR-MS/MS. The following metabolic steps could be postulated: hydrolysis of the amide, N-oxide formation, N- and/or O-demethylation, oxidation of the piperazine ring to the corresponding keto-piperazine, piperazine ring opening followed by oxidation of a methylene group to the corresponding imide, and hydroxylation of the phenyl group. Furthermore, N-acetylation, glucuronidation and sulfation were observed. Using human CYPs, CYP1A2, CYP2C19, CYP2D6, and/or CYP3A4 were found to catalyze N-oxide formation and N-, O-demethylation and/or oxidation. Mostly MeOP and N-oxide-MeOP but to a minor degree also other metabolites could be detected in the GC-MS and LC-MS(n) SUSAs.

Metabolite identification of the antimalarial piperaquine in vivo using liquid chromatography–high‐resolution mass spectrometry in combination with multiple data‐mining tools in tandem

“…Most likely, hydroxylation at the piperazine group could lead to unstable metabolites, which did not exist with detectable concentration levels. Oxidation of a methylene group on the piperazine ring leading to the corresponding keto‐piperazine or ring‐opening of piperazine has been described in previous studies, such as trimetazidine (Jackson et al , ) and a psychoactive substance methoxypiperamide (Meyer et al , ). In addition, PQ and its major metabolites could show multiple chromatographic peaks with similar MS/MS profiles owing to their multiple p K a values (Kjellin et al , ; Lindegardh et al , ).…”

Microbial biotransformation of five pyrrolidinophenone‐type psychoactive substances in wastewater and a wastewater isolated Pseudomonas putida strain

“…In contrast, the main alpha‐cleaved fragment ion in the TPs with a carbon‐bonded hydroxylation in the pyrrolidine ring ( Ib , IIIb , Vb ), carried the oxygen, which indicated a bond with a higher stability in the collision cell. All detected N‐ oxides eluted after the unchanged compound (Table ), whereas carbon‐bonded hydroxylation usually elutes before the unchanged compound using reversed phase chromatography . So far, metabolism studies of MPHP, MPBP, and MOPPP have only been analyzed using GC–MS, where N‐ oxides are not observed.…”

“…All detected N-oxides eluted after the unchanged compound (Table 2), whereas carbon-bonded hydroxylation usually elutes before the unchanged compound using reversed phase chromatography. [11,[32][33][34] So far, metabolism studies of MPHP, MPBP, and MOPPP have only been analyzed using GC-MS, where N-oxides are not observed. Evaluation on microbial biotransformation of environmentally relevant compounds, including pharmaceuticals, using activated sludge models have reported N-oxide formation of tertiary nitrogens.…”

Mass spectrometric strategies for the investigation of biomarkers of illicit drug use in wastewater

“…A suitable strategy to investigate metabolites and TPs makes use of “in vitro” or “in vivo” metabolism experiments , and of laboratory or field‐degradation experiments under controlled conditions, which can identify known and unknown metabolites or TPs of selected drugs, respectively. In the recent literature, several examples can be found that deal with the investigation of drug metabolites with in vitro or in vivo experiments (Pozo et al, ; Takayama et al, ; Holm et al, ; Meyer et al, ; Ibáñez et al, ). These experiments are very useful and allow the discovery of metabolites, which might be expected and detected in wastewater, and are, therefore, potential target IDBs in future WBE‐based studies.…”