Phase I metabolism of the carbazole-derived synthetic cannabinoids EG-018, EG-2201, and MDMB-CHMCZCA and detection in human urine samples

Study of the Metabolic Profiles of "Indazole-3-Carboxamide" and "Isatin Acyl Hydrazone" (OXIZID) Synthetic Cannabinoids in a Human Liver Microsome Model Using UHPLC-QE Orbitrap MS

Unregulated core structures, "isatin acyl hydrazones" (OXIZIDs), have quietly appeared on the market since China legislated to ban seven general core scaffolds of synthetic cannabinoids (SCs). The fast evolution of SCs presents clinical and forensic toxicologists with challenges. Due to extensive metabolism, the parent compounds are barely detectable in urine. Therefore, studies on the metabolism of SCs are essential to facilitate their detection in biological matrices. The aim of the present study was to elucidate the metabolism of two cores, "indazole-3-carboxamide" (e.g., ADB-BUTINACA) and "isatin acyl hydrazone" (e.g., BZO-HEXOXIZID). The in vitro phase I and phase II metabolism of these six SCs was investigated by incubating 10 mg/mL pooled human liver microsomes with co-substrates for 3 h at 37 °C, and then analyzing the reaction mixture using ultrahigh-performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry. In total, 9 to 34 metabolites were detected for each SC, and the major biotransformations were hydroxylation, dihydrodiol formation (MDMB-4en-PINACA and BZO-4en-POXIZID), oxidative defluorination (5-fluoro BZO-POXIZID), hydrogenation, hydrolysis, dehydrogenation, oxidate transformation to ketone and carboxylate, N-dealkylation, and glucuronidation. Comparing our results with previous studies, the parent drugs and SC metabolites formed via hydrogenation, carboxylation, ketone formation, and oxidative defluorination were identified as suitable biomarkers.

Comparison between human liver microsomes and the fungus Cunninghamella elegans for biotransformation of the synthetic cannabinoid JWH-424 having a bromo-naphthyl moiety analysed by high-resolution mass spectrometry

PURPOSE

JWH-424, (8-bromo-1-naphthyl)(1-pentyl-1H-indol-3-yl)methanone, is a synthetic cannabinoid, which is a brominated analogue of JWH-018, one of the best-known synthetic cannabinoids. Despite the structural similarity to JWH-018, little is known about JWH-424 including its metabolism. The aim of the study was to compare human liver microsomes (HLM) and the fungus Cunninghamella elegans as the metabolism catalysts for JWH-424 to better understand the characteristic actions of the fungus in the synthetic cannabinoid metabolism.

METHODS

JWH-424 was incubated with HLM for 1 h and Cunninghamella elegans for up to 72 h. The HLM incubation mixtures were diluted with methanol and fungal incubation mixtures were extracted with dichloromethane and reconstituted in methanol before analyses by liquid chromatography-high-resolution mass spectrometry (LC-HRMS).

RESULTS

HLM incubation resulted in production of ten metabolites through dihydrodiol formation, hydroxylation, and/or ipso substitution of the bromine with a hydroxy group. Fungal incubation led to production of 23 metabolites through carboxylation, dihydrodiol formation, hydroxylation, ketone formation, glucosidation and/or sulfation.

CONCLUSIONS

Generally, HLM models give good predictions of human metabolites and structural analogues are metabolised in a similar fashion. However, major hydroxy metabolites produced by HLM were those hydroxylated at naphthalene instead of pentyl moiety, the major site of hydroxylation for JWH-018. Fungal metabolites, on the other hand, had undergone hydroxylation mainly at pentyl moiety. The metabolic disagreement suggests the necessity to verify the human metabolites in authentic urine samples, while H9 and H10 (hydroxynaphthalene), H8 (ipso substitution), F22 (hydroxypentyl), and F17 (dihydroxypentyl) are recommended for monitoring of JWH-424 in urinalysis.

Metabolism of third generation synthetic cannabinoids using zebrafish larvae

Synthetic cannabinoids are the second largest group of new psychoactive substances reported by the United Nations Office on Drugs and Crime in the last decade and case reports bring attention to its high potency effects and its severe toxicity, including fatalities. Moreover, synthetic cannabinoids are usually entirely metabolized and metabolic pathways for many new generation synthetic cannabinoids are still unknown. In this study, the metabolism of five third generation synthetic cannabinoids was evaluated using zebrafish (Danio rerio) larvae as 24-h in vivo model studied within 5 days after fertilization. The studied synthetic cannabinoids were MMB-CHMICA, ADB-CHMICA, ADB-CHMINACA, MDMB-CHMCZCA, and NNL-3, and the respective metabolites were identified by liquid chromatography-high resolution tandem mass spectrometry. Eleven, six, fourteen, eleven, and four metabolites were identified for MMB-CHMICA, ADB-CHMICA, ADB-CHMINACA, MDMB-CHMCZCA, and NNL-3, respectively, and metabolic pathways have been proposed. The use of zebrafish larvae, with a high degree of physiological and genetic homology to humans, is an emerging tool very useful for the identification of metabolic pathways of psychoactive substances. Results obtained in this study compared well with metabolites obtained previously for the same target molecules or structural analogous after in vitro incubation with human or rat hepatocytes. Thus, potential biomarkers for the evaluated compounds are the O-demethylated metabolite for MMB-CHMICA; the oxidative deamination to hydroxyl metabolite for ADB-CHMICA; hydroxyl metabolites at cyclohexylmethyl, tert-butyl, and indazole moieties for ADB-CHMINACA; hydroxyl metabolites at carbazole core, tert-butyl, or cyclohexylmethyl tail moieties for MDMB-CHMCZCA; and amide hydrolyzed, defluorinated, and dihydroxilated metabolite for NNL-3.

Synthetic cannabinoid receptor agonists and their human metabolites in sewage water: Stability assessment and identification of transformation products

Since their first appearance in 2008, synthetic cannabinoid receptor agonists (SCRAs) remain the most popular new psychoactive substances (NPS) in the EU. Following consumption, these drugs and their metabolites are urinary excreted and enter the sewage system enabling the application of wastewater-based epidemiology (WBE). Knowing the fate of target analytes in sewage water is essential for successful application of WBE. This study investigates the stability of several chemically diverse SCRAs and selected human metabolites under sewage conditions utilizing a combination of liquid chromatography-tandem mass spectrometry and high-resolution mass spectrometry (HRMS). Target analytes included SCRAs with indole (5F-PB-22, PB-22 pentanoic acid), indazole (AMB-FUBINACA, 5F-ADB, 5F-ADB dimethylbutanoic acid), carbazole (MDMB-CHMCZCA, EG-018), and γ-carboline (Cumyl-PeGaClone) chemical core structures representing most of the basic core structures that have occurred up to now. Stability tests were performed using wastewater effluent containing 5% activated sludge as inoculum to monitor degradation processes and formation of transformation products (TPs). The majority of investigated SCRAs, excluding the selected human metabolites, was recalcitrant to microbial degradation in sewage systems over a period of 29 days. Their stability was rather controlled by physico-chemical processes like sorption and hydrolysis. Considering a typical hydraulic in-sewer retention time of 24 h, the concentration of AMB-FUBINACA decreased by 90% thus representing the most unstable SCRA investigated in this study. Among the 10 newly identified TPs, three could be considered as relevant markers and should be included into future WBE studies to gain further insight into use and prevalence of SCRAs on the drug market.

Determination of Third-Generation Synthetic Cannabinoids in Oral Fluids

A procedure has been developed for the determination of third-generation synthetic cannabinoids in oral fluid samples by using a semi-automated microextraction by packed sorbent (MEPS) procedure and gas chromatography-mass spectrometry (GC-MS) determination. Five synthetic cannabinoids were employed as model compounds 5F-ADB, MMB-CHMICA, THJ-2201, CUMYL-4CN-BINACA and MDMB-CHMCZCA. The most adequate operative conditions for MEPS were evaluated giving quantitative recoveries, from 89 to 124%, in synthetic and field saliva samples spiked with 125 and 250 μg/L of the studied cannabinoids, with the exception of MDMB-CHMCZCA in field saliva samples that provided slightly lower recoveries from 62 to 66%. A high sensitivity was obtained for the proposed MEPS-GC-MS procedure with limits of detection from 10 to 20 μg/L. The obtained results demonstrate the high potential of MEPS-GC-MS combination for semi-automated, selective and sensitive determination of synthetic cannabinoids in oral fluid samples.

Recent bionalytical methods for the determination of new psychoactive substances in biological specimens

One of the problems associated with the consumption of new psychoactive substances is that in most scenarios of acute toxicity the possibility of quick clinical action may be impaired because many screening methods are not responsive to them, and laboratories are not able to keep pace with the appearance of new substances. For these reasons, developing and validating new analytical methods is mandatory in order to efficiently face those problems, allowing laboratories to be one step ahead. The goal of this work is to perform a critical review regarding bionalytical methods that can be used for the determination of new psychoactive substances (phenylethylamines, cathinones, synthetic cannabinoids, opioids, benzodiazepines, etc), particularly concerning sample preparation techniques and associated analytical methods.

Interpol review of toxicology 2016-2019

This review paper covers the forensic-relevant literature in toxicology from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20.Papers%202019.pdf.

In vitro and in vivo pharmacological evaluation of the synthetic cannabinoid receptor agonist EG-018

Synthetic cannabinoid receptor agonists (SCRAs) possess high abuse liability and complex toxicological profiles, making them serious threats to public health. EG-018 is a SCRA that has been detected in both illicit products and human samples, but it has received little attention to date. The current studies investigated EG-018 at human CB₁ and CB₂ receptors expressed in HEK293 cells in [³H]CP55,940 competition binding, [³⁵S]GTPγS binding and forskolin-stimulated cAMP production. EG-018 was also tested in vivo for its ability to produce cannabimimetic and abuse-related effects in the cannabinoid tetrad and THC drug discrimination, respectively. EG-018 exhibited high affinity at CB₁ (21 nM) and at CB₂ (7 nM), but in contrast to typical SCRAs, behaved as a weak partial agonist in [³⁵S]GTPγS binding, exhibiting lower efficacy but greater potency, than that of THC at CB₁ and similar potency and efficacy at CB₂. EG-018 inhibited forskolin-stimulated cAMP with similar efficacy but lower potency, compared to THC, which was likely due to high receptor density facilitating saturation of this signaling pathway. In mice, EG-018 (100 mg/kg, 30 min) administered intraperitoneally (i.p.) did not produce effects in the tetrad or drug discrimination nor did it shift THC's ED₅₀ value in drug discrimination when administered before THC, suggesting EG-018 has negligible occupancy of brain CB₁ receptors following i.p. administration. Following intravenous (i.v.) administration, EG-018 (56 mg/kg) produced hypomotility, catalepsy, and hypothermia, but only catalepsy was blocked by the selective CB₁ antagonist rimonabant (3 mg/kg, i.v.). Additional studies of EG-018 and its structural analogues could provide further insight into how cannabinoids exert efficacy through the cannabinoid receptors.

Adding more "spice" to the pot: A review of the chemistry and pharmacology of newly emerging heterocyclic synthetic cannabinoid receptor agonists

Synthetic cannabinoid receptor agonists (SCRAs) first appeared on the international recreational drug market in the early 2000s in the form of SCRA-containing herbal blends. Due to the cannabimimetic effects associated with the consumption of SCRAs, they have acquired an ill-informed reputation for being cheap, safe, and legal alternatives to illicit cannabis. Possessing high potency and affinity for the human cannabinoid receptor subtype-1 (CB₁ ) and -2 (CB₂ ), it is now understood that the recreational use of SCRAs can have severe adverse health consequences. The major public health problem arising from SCRA use has pressed legislators around the world to employ various control strategies to curb their recreational use. To circumvent legislative control measures, SCRA manufacturers have created a wide range of SCRA analogs that contain, more recently, previously unencountered azaindole, γ-carbolinone, or carbazole heterocyclic scaffolds. At present, little information is available regarding the chemical syntheses of these newly emerging classes of SCRA, from a clandestine perspective. When compared with previous generations of indole- and indazole-type SCRAs, current research suggests that many of these heterocyclic SCRA analogs maintain high affinity and efficacy at both CB₁ and CB₂ but largely evade legislative control. This review highlights the importance of continued research in the field of SCRA chemistry and pharmacology, as recreational SCRA use remains a global public health issue and represents a serious control challenge for law enforcement agencies.

In vitro metabolic profiling of synthetic cannabinoids by pooled human liver microsomes, cytochrome P450 isoenzymes, and Cunninghamella elegans and their detection in urine samples

As synthetic cannabinoids are extensively metabolized, there is an urgent need for data on which metabolites can be used for successful urine screening. This study examines the in vitro metabolism of EG-018 and its 5F-analogue EG-2201 by means of comparing three different in vitro models: pooled human liver microsomes, cytochrome P450 isoenzymes, and a fungal approach utilizing the filamentous fungus Cunninghamella elegans LENDNER, which is known for its ability to mimic human biotransformation of xenobiotics. In addition, this study includes the screening of two authentic urine samples from individuals with proven EG-018 consumption, for the evaluation of in vitro-in vivo extrapolations made in the study. Incubation with pooled human liver microsomes yielded 15 metabolites of EG-018 belonging to six different metabolite subgroups, and 21 metabolites of EG-2201 belonging to seven different metabolite subgroups, respectively. Incubation with cytochrome P450 isoenzymes incubation yielded a further three EG-018 and five EG-2201 metabolites. With reference to their summed metabolite peak abundancies, the isoenzymes CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5 were shown to contribute most to the microsomal metabolism of EG-018 and EG-2201. CYP2B6 was shown to make the lowest contribution, by far. As the phase I metabolism of both synthetic cannabinoids was shown to be distributed over a substantial number of different cytochrome P450 isoenzymes, it was concluded that it is likely to not be significantly affected by co-consumption of other drugs. Although fungal incubation with Cunninghamella elegans yielded an additional three EG-018 and four EG-2201 metabolites not observed after microsomal incubation, metabolites generated by Cunninghamella elegans were in good correlation with those generated by microsomal incubations. The fungal model demonstrated its ability to be an independent in vitro model in synthetic cannabinoid metabolism research. The three tested in vitro models enable sufficient predictive in vitro-in vivo extrapolations, comparable to those obtained from hepatocyte incubation published in the literature. In addition, with regard to the screening of authentic urine samples and comparison with the literature, one monohydroxylated EG-018 metabolite and two monohydroxylated EG-2201 metabolites can be recommended as urinary targets, on the basis of the tested in vitro models. Graphical abstract.

Synthetic Cannabinoid Hydroxypentyl Metabolites Retain Efficacy at Human Cannabinoid Receptors

Synthetic cannabinoids (SCs) are novel psychoactive substances that are easily acquired, widely abused as a substitute for cannabis, and associated with cardiotoxicity and seizures. Although the structural bases of these compounds are scaffolds with known affinity and efficacy at the human cannabinoid type-1 receptor (hCB1), upon ingestion or inhalation they can be metabolized to multiple chemical entities of unknown pharmacological activity. A large proportion of these metabolites are hydroxylated on the pentyl chain, a key substituent that determines receptor affinity and selectivity. Thus, the pharmacology of SC metabolites may be an important component in understanding the in vivo effects of SCs. We examined nine SCs (AB-PINACA, 5F-AB-PINACA, ADB/MDMB-PINACA, 5F-ADB, 5F-CUMYL-PINACA, AMB-PINACA, 5F-AMB, APINACA, and 5F-APINACA) and their hydroxypentyl (either 4-OH or 5-OH) metabolites in [3H]CP55,940 receptor binding and the [35S]GTPγS functional assay to determine the extent to which these metabolites retain activity at cannabinoid receptors. All of the SCs tested exhibited high affinity (<10 nM) and efficacy for hCB1 and hCB2 The majority of the hydroxypentyl metabolites retained full efficacy at hCB1 and hCB2, albeit with reduced affinity and potency, and exhibited greater binding selectivity for hCB2 These data suggest that phase I metabolites may be contributing to the in vivo pharmacology and toxicology of abused SCs. Considering this and previous reports demonstrating that metabolites retain efficacy at the hCB1 receptor, the full pharmacokinetic profiles of the parent compounds and their metabolites need to be considered in terms of the pharmacological effects and time course associated with these drugs.

Suspect and non-target screening workflows to investigate the in vitro and in vivo metabolism of the synthetic cannabinoid 5Cl-THJ-018

The use of synthetic cannabinoids causes similar effects as Δ⁹ -tetrahydrocannabinol and long-term (ab)use can lead to health hazards and fatal intoxications. As most investigated synthetic cannabinoids undergo extensive biotransformation, almost no parent compound can be detected in urine, which hampers forensic investigations. Limited information about the biotransformation products of new synthetic cannabinoids makes the detection of these drugs in various biological matrices challenging. This study aimed to identify the main in vitro biotransformation pathways of 5Cl-THJ-018 and to compare these findings with an authentic urine sample of a 5Cl-THJ-018 user. The synthetic cannabinoid was incubated with pooled human liver microsomes and cytosol to simulate phase I and phase II biotransformations. Resulting extracts were analyzed with liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Three different data analysis workflows were applied to identify biotransformation products. A suspect screening workflow used an in-house database built from literature data and in silico biotransformation predictions. Two non-target screening workflows used a commercially available software and an open-source software for mass spectrometry data processing. A total of 23 in vitro biotransformation products were identified, with hydroxylation, oxidative dechlorination, and dihydrodiol formation pathways as the main phase I reactions. Additionally, five glucuronidated and three sulfated phase II conjugates were identified. The predominant in vivo pathway was through oxidative dechlorination and in total six metabolites of 5Cl-THJ-018 were identified. Biotransformation products both in vitro and in vivo were successfully identified using complementary suspect and non-target screening workflows.

Human phase I metabolism of the novel synthetic cannabinoid 5F-CUMYL-PEGACLONE

PURPOSE

5F-CUMYL-PEGACLONE is a recently emerged γ-carbolinone derived synthetic cannabinoid. The present study aimed to identify phase I metabolites to reliably prove consumption of the substance by urine analysis and to differentiate from the uptake of the non-fluorinated analog CUMYL-PEGACLONE.

METHODS

For metabolite characterization, phase I metabolites were analyzed by liquid chromatography-high resolution mass spectrometry after incubation with pooled human liver microsomes. Reliability of the biomarkers was evaluated by analysis of human urine samples (n = 20) by liquid chromatography-triple quadrupole tandem mass spectrometry. Sample preparation included β-glucuronidase treatment followed by liquid-liquid extraction.

RESULTS

In total, 15 metabolites were detected in vivo and characterized. Metabolic reactions were primarily observed at the γ-carbolinone core and the 5-fluoropentyl chain, and included N-dealkylation, hydroxylation, hydrolytic defluorination, formation of a dihydrodiol, oxidation to the pentanoic acid metabolite and formation of the propionic acid metabolite. Six of these metabolites were identical with phase I metabolites of CUMYL-PEGACLONE, which must be considered for interpretation of analytical findings in urine samples.

CONCLUSIONS

5F-CUMYL-PEGACLONE was subject to extensive metabolism in humans. The propionic acid metabolite was the most abundant metabolite in all urine samples and should be targeted when maximum sensitivity is needed (e.g., drug abstinence control). However, this metabolite also occurs in the biotransformation of the non-fluorinated analog and is, therefore, not a compound-specific marker. For differentiation, a metabolite hydroxylated at the γ-carbolinone core showed to be the most reliable marker and should be used as an additional target analyte.