Abstract
Synthetic cannabinoids (SCs), originally sold as herbal mixtures for smoking since the mid-2000s, have become one of the most prevalent drug classes within new psychoactive substances (NPS). SCs have heterogeneous chemistries, the structural evolution having rapidly evolved from the first generation to the fourth or latest generation by clandestine laboratories. The substances can be unexpectedly toxic and harmful since they are produced by unregulated clandestine laboratories, therefore, little is known about their purity or potency towards cannabinoid (CB1 and CB2) receptors. SCs are still posing a health threat to the public due to their psychoactive and peripheral toxic effects. Their toxicology and pharmacology are mostly unknown due to the dynamic nature of these recreational drugs.The aim of the project was to conduct a detailed analytical study of SCs and their metabolites and explore several analytical challenges with respect to their detection and identification: (1) Investigation of alternative formulations containing SCs in order to identify potentially harmful substances in these commercial products; (2) Studies on the biotransformation and pyrolysis products of SCs in order to understand the metabolism and pyrolysis of selected SCs; (3) Studies on the formation of new analytical markers due to SCs and alcohol concomitant administration to produce SC-ethyl esters, which could further complicate their toxicological profile. Furthermore, a liquid chromatography-high resolution mass spectrometric (LC-HRMS) method for the detection and quantification of several SCs, their metabolites and SC-ethyl esters in human plasma was developed and validated. Finally, clinical samples from an emergency department in London as well as post-mortem forensic samples were analysed for SCs to enable prevalence to be assessed.
The metabolism of SCs is relevant in clinical and forensic toxicology, as SC metabolites are widely used as markers for identifying SC intake. Poly-drug use represents another significant concern related to SCs, which may augment the toxicity profiles of SCs; as recently reported by the United Nations Office on Drugs and Crime, antipsychotic, cannabis and alcohol were the three most frequently detected substances in conjunction with fatality cases involving SCs. This work reports the discovery of a new indicator -‘the SC-ethyl ester’ - resulting from SCs and alcohol co-consumption. The new metabolite SC-ethyl ester is hereby proposed to be used as a new marker of SC-alcohol concomitant misuse. This species was produced and detected (in vitro using HLM systems) when SCs containing labile ester functional groups reacted with ethanol via esterase-mediated transesterification. Method validation for the semi-quantitative screening was performed to detect and identify these SCs and new metabolites in biological matrices with the aim to investigate in vivo production of these novel markers in real cases using clinical and forensic samples. A retrospective forensic toxicology analysis revealed detection 5F-PB-22-ethyl ester in a post-mortem blood sample from more than 5 years ago, thus suggesting the concomitant presence of 5F-PB-22 and ethanol in that sample.
An LC-HRMS method with liquid–liquid extraction for the quantification of 28 SC parent compounds and 6 SC-ethyl esters in human plasma was developed and validated according to the SWGTOX guidelines using JWH-018-4-hydroxy pentyl-d5 as an internal standard. The method proved to be suitable for the identification and quantification of SCs and SC-ethyl esters in human plasma. The linear calibration curve ranged from 1 to 25 ng/mL with R2 values approaching 0.98. The LLOQ ranged from 1 to 2.5 ng/mL. Accuracy and precision were assessed at LLOQ, 10 and 25 ng/mL. The accuracy was considered acceptable ranging from 82 % to 111.4 % and precision (interday) is in the range of 0.3 % - 16.1 %. The method was successfully applied to 250 plasma samples collected from an emergency department in London during 2018-2019. 5F-MDMB-PICA and 4F-MDMB-BINACA were detected in 25 and 22 cases, respectively. Several samples were found to contain both compounds in the same plasma sample. The metabolite, 5F-MDMB-PICA-desfluoro hydroxy, has been detected alongside 5F-MDMB-PICA in 25 cases. 4F-MDMB-BINACA-desfluoro hydroxy, was detected alongside 4F-MDMB-BINACA in 8 cases. No ethyl ester and pyrolysis markers were detected in these clinical plasma samples, whereas a retrospective analysis in blood from a post-mortem case did find the ethyl ester species. It was concluded that the markers and also parent compound itself can be used to indicate trends in use and prevalence of SCs changing over time.
| Date of Award | 1 Jul 2022 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Vincenzo Abbate (Supervisor) & David Cowan (Supervisor) |