The metabolic fate of two new psychoactive substances - 2-aminoindane and N-methyl-2-aminoindane - studied in vitro and in vivo to support drug testing

Target and suspect screening of (new) psychoactive substances in South Korean wastewater by LC-HRMS

New psychoactive substances (NPS) are a type of abused drug designed to mimic the effects of the currently known illicit drugs, whose structures are constantly changing to escape surveillance. The quick identification of NPS use in the community therefore demands immediate action. This study aimed to develop a target and suspect screening method using LC-HRMS to identify NPS in wastewater samples. An in-house database of 95 traditional and NPS was built using the reference standards, and an analytical method was developed. Wastewater samples were collected from 29 wastewater treatment plants (WWTP) across South Korea, representing 50 % of the total population. The psychoactive substances in waste water samples were screened using in-house database and developed analytical methods. A total of 14 substances were detected in the target analysis, including three NPS (N-methyl-2-AI, 25E-NBOMe, and 25D-NBOMe) and 11 traditional psychoactive substances and their metabolites (zolpidem phenyl-4-COOH, ephedrine, ritalinic acid, tramadol, phenmetrazine, phendimetrazine, phentermine, methamphetamine, codeine, morphine, and ketamine). Out of these, N-methyl-2-AI, zolpidem phenyl-4-COOH, ephedrine, ritalinic acid, tramadol, phenmetrazine, and phendimetrazine were detected with a detection frequency of over 50 %. Primarily, N-methyl-2-Al was detected in all the wastewater samples. Additionally, four NPSs (amphetamine-N-propyl, benzydamine, isoethcathinone, methoxyphenamine) were tentatively identified at level 2b in a suspect screening analysis. This is the most comprehensive study to investigate NPS using target and suspect analysis methods at the national level. This study raises a need for continuous monitoring of NPS in South Korea.

Metabolic study of new psychoactive substance methoxpropamine in mice by UHPLC-QTOF-HRMS

Methoxpropamine (MXPr) is an arylcyclohexylamine dissociative drug structurally similar to 3-methoxyeticyclidine, ketamine, and deschloroketamine, recently appeared in the European illegal market, and was classified within the new psychoactive substances (NPS). Our study investigated the metabolism of MXPr to elucidate the distribution of the parent drug and its metabolites in body fluids and fur of 16 mice. After the intraperitoneal administration of MXPr (1, 3, and 10 mg/kg), urine samples from eight male and eight female mice were collected every hour for six consecutive hours and then at 12- to 24-h intervals. Additionally, plasma samples were collected 24 h after MXPr (1 and 3 mg/kg) administration. Urine and plasma were diluted 1:3 with acetonitrile/methanol (95:5) and directly injected into the UHPLC-QTOF-HRMS system. The phase-I and phase-II metabolites were preliminarily identified by means of the fragmentation patterns and the exact masses of both their precursor and fragment ions. Lastly, the mice fur was analyzed following an extraction procedure specific for the keratin matrix. Desmethyl-MXPr-glucoronide was identified in urine as the main metabolite, detected up to 24 h after administration. The presence of norMXPr in urine, plasma, and fur was also relevant, following a N-dealkylation process of the parent drug. Other metabolites that were identified in fur and plasma included desmethyl-MXPr and dihydro-MXPr. Knowledge of the MXPr metabolites evolution is likely to support their introduction as target compounds in NPS toxicological screening analysis on real samples, both to confirm intake and extend the detection window of the dissociative drug MXPr in the biological matrices.

Behavioral and Pharmacokinetics Studies of N-Methyl-2-Aminoindane (NM2AI) in Mice: An Aminoindane Briefly Used in the Illicit Drug Market

Drug forums are considered as the main platform sources that have contributed to the increase in NPS popularity, especially for those not yet known to law enforcement and therefore not yet illegal. An example is the new synthetic stimulant NM2AI, which has a very short history of human use and abuse. Little is known regarding this compound, but some information from internet forums and the scientific literature indicates NM2AI as a structural derivate of MDAI, which is known for its entactogenic activity. Indeed, the purpose of this study is to evaluate, for the first time, the in vivo acute effect induced by the intraperitoneal injection of NM2AI (1-10-30-100 mg/kg) in mice. We demonstrate the sensory (by visual placing and object tests) and physiological (core temperature measurement) function variations, nociceptor (by tail pinch test) and strength (grip test) alterations, and sensorimotor (time on rod and mobility) decrease. Moreover, we verify the mild hallucinogenic effect of NM2AI (by startle/prepulse inhibition test). Lastly, we perform a pharmacokinetic study on mice blood samples, highlighting that the main active metabolite of NM2AI is 2-aminoindane (2AI). Taken together, our data confirm the suspected entactogenic activity of NM2AI; however, these in vivo effects appear atypical and less intense with respect to those induced by the classic stimulants, in surprising analogy with what is reported by networked users.

An Update on the Implications of New Psychoactive Substances in Public Health

The emergence of new psychoactive substances has earned a great deal of attention, and several reports of acute poisoning and deaths have been issued involving, for instance, synthetic opiates. In recent years, there have been profound alterations in the legislation concerning consumption, marketing, and synthesis of these compounds; rapid alert systems have also been subject to changes, and new substances and new markets, mainly through the internet, have appeared. Their effects and how they originate in consumers are still mostly unknown, primarily in what concerns chronic toxicity. This review intends to provide a detailed description of these substances from the point of view of consumption, toxicokinetics, and health consequences, including case reports on intoxications in order to help researchers and public health agents working daily in this area.

Can a Recently Developed Pig Model Be Used for In Vivo Metabolism Studies of 7-Azaindole-Derived Synthetic Cannabinoids? A Study Using 5F-MDMB-P7AICA

New psychoactive substances (NPS), especially synthetic cannabinoids (SC) remain a public health concern. Due to ethical reasons, systematic controlled human studies to elucidate their toxicodynamics and/or toxicokinetics are usually not possible. However, such knowledge is necessary, for example, for determination of screening targets and interpretation of clinical and forensic toxicological data. In the present study, the feasibility of the pig model as an alternative for human in vivo metabolism studies of SC was investigated. For this purpose, the metabolic pattern of the SC methyl-2-{[1-(5-fluoropentyl)-1H-pyrrolo[2,3-b]pyridine-3-carbonyl]amino}-3,3-dimethylbutanoate (5F-MDMB-P7AICA) was elucidated in pig urine following inhalative administration (dosage: 200 µg/kg of body weight). The results were compared with human and pig liver microsomal assays and literature. In addition, different incubations with isolated cytochrome-P450 (CYP) monooxygenases were conducted to identify the involved isozymes. In total, nine phase I and three phase II metabolites were identified in pig urine. The most abundant reactions were ester hydrolysis, ester hydrolysis combined with glucuronidation and ester hydrolysis combined with hydroxylation at the tert-butyl moiety. The parent compound was only found up to 1 h after administration in pig urine. The metabolite formed after hydroxylation and glucuronidation was detectable for 2 h, the one formed after ester hydrolyzation and defluorination for 4 h after administration. All other metabolites were detected during the whole sampling time. The most abundant metabolites were also detected using both microsomal incubations and monooxygenase screenings revealed that CYP3A4 catalyzed most reactions. Finally, pig data showed to be in line with published human data. To conclude, the main metabolites recommended in previous studies as urinary targets were confirmed by using pig urine. The used pig model seems therefore to be a suitable alternative for in vivo metabolism studies of 7-azaindole-derived SC.

Metabolism Study of N-Methyl 2-Aminoindane (NM2AI) and Determination of Metabolites in Biological Samples by LC-HRMS

Since the widespread diffusion of new psychoactive substances, forensic laboratories are often required to identify new drugs and their metabolites for which information or reference standards are lacking. We performed a study on N-methyl-2-aminoindane (NM2AI) metabolism in silico and in vivo, in order to identify the main metabolites to be screened in the different biological samples. We performed the in silico metabolism prediction of NM2AI using MetaSiteTM software and subsequently verified the presence of metabolites in the blood, urine and hair of mice after NM2AI administration. The samples were analyzed by liquid chromatography-high-resolution mass spectrometry (LC-HRMS) with a benchtop Orbitrap Exactive mass detector. This allowed the evaluation of the agreement between software prediction and experimental results in biological samples. LC-HRMS analysis identified seven main metabolites in the urine. They were identified, by their accurate masses and fragmentation patterns, as 2-aminoindane (2AI), two hydroxy-2AI and four hydroxy-NM2AI; one of the hydroxy-NM2AI and one of the hydroxy-2AI underwent also to conjugation. NM2AI and 2AI were also detected by LC-HRMS in the hair and blood. Based on these findings, we developed an LC-HRMS method for the screening of NM2AI and metabolites in urine, blood and hair samples. This can be of primary effectiveness to uncover the abuse of NM2AI and related possible intoxications.

Gas chromatography-mass spectrometry of eight aminoindanes: 2-Aminoindane, N-methyl-2-, 5-methoxy-, 5-methoxy-6-methyl-, 4,5-methylenedioxy-, 5,6-methylenedioxy- and 5-iodo-2-aminoindane, and rasagiline

RATIONALE

Aminoindanes are one class of many new psychoactive substances that have emerged over the last decade. Analogues of 2-aminoindane (2-AI) are being encountered in crime laboratories and analytical data for most aminoindanes are limited. Interpretation and optimization of gas chromatography-mass spectrometry data will enhance reliability in characterizing aminoindanes.

METHODS

This study focuses on the electron ionization mass spectrometric fragmentation of eight aminoindane analogues and the gas chromatographic separation of these eight aminoindane analogues using four different column stationary phases, Rxi®-1Sil MS, Rxi®-5Sil MS, Rxi®-35Sil MS, and Rxi®-624Sil MS. Split injection (25:1) was utilized and each column had the same configuration (30 m × 25 mm × 0.25 μm), with the exception of the Rxi®-624Sil MS column (30 m × 25 mm ×1.4 μm).

RESULTS

Mass spectra showed strong molecular ions for all aminoindanes, except for rasagiline that produced a uniquely abundant [M - 1] ion. Other characteristic fragmentation that was present for all the aminoindanes included indane and indene ions (m/z 115-117), the tropylium ion (m/z 91), and subsequent loss of diene to produce smaller ions that followed: phenyl (m/z 77), cyclopentadienyl (m/z 65), cyclobutadienyl (m/z 51), and cyclopropenyl (m/z 39).

CONCLUSIONS

Separation of eight aminoindanes was optimized, and linear retention indices were determined for the compounds on four capillary columns. Based on the retention data, all eight aminoindanes were resolved on an Rxi®-624Sil MS column. Each aminoindane exhibited unique fragmentation ions in the mass spectra to distinguish between similar analogues. The results of this study will strengthen the analytical profiles of 2-AI and seven analogues, assisting forensic scientists in their analysis and identification of these substances.

Liquid Chromatography-High-Resolution Mass Spectrometry-Based In Vitro Toxicometabolomics of the Synthetic Cathinones 4-MPD and 4-MEAP in Pooled Human Liver Microsomes

Synthetic cathinones belong to the most often seized new psychoactive substances on an international level. This study investigated the toxicometabolomics, particularly the in vitro metabolism of 2-(methylamino)-1-(4-methylphenyl)-1-pentanone (4-MPD) and 2-(ethylamino)-1-(4-methylphenyl)-1-pentanone (4-MEAP) in pooled human liver microsomes (pHLM) using untargeted metabolomics techniques. Incubations were performed with the substrates in concentrations ranging from 0, 12.5, and 25 µM. Analysis was done by means of high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC-HRMS/MS) in full scan only and the obtained data was evaluated using XCMS Online and MetaboAnalyst. Significant features were putatively identified using a separate parallel reaction monitoring method. Statistical analysis was performed using Kruskal-Wallis test for prefiltering significant features and subsequent hierarchical clustering, as well as principal component analysis (PCA). Hierarchical clustering or PCA showed a distinct clustering of all concentrations with most of the features z-scores rising with the concentration of the investigated substances. Identification of significant features left many of them unidentified but revealed metabolites of both 4-MPD and 4-MEAP. Both substances formed carboxylic acids, were hydroxylated at the alkyl chain, and formed metabolites after combined hydroxylation and reduction of the cathinone oxo group. 4-MPD additionally formed a dihydroxy metabolite and a hydroxylamine. 4-MEAP was additionally found reduced at the cathinone oxo group, N-dealkylated, and formed an oxo metabolite. These findings are the first to describe the metabolic pathways of 4-MPD and to extend our knowledge about the metabolism of 4-MEAP. Findings, particularly the MS data of the metabolites, are essential for setting up metabolite-based toxicological (urine) screening procedures.