Focusing on the 5F-MDMB-PICA, 4F-MDMB-BICA synthetic cannabinoids and their primary metabolites in analytical and pharmacological aspects.

Nowadays, more and more new synthetic cannabinoids (SCs) appearing on the illicit market present challenges to analytical, forensic, and toxicology experts. For a better understanding of the physiological effect of SCs, the key issue is studying their metabolomic and psychoactive properties. In this study, our validated targeted reversed phase UHPLC-MS/MS method was used for determination of urinary concentration of 5F-MDMB-PICA, 4F-MDMB-BICA, and their primary metabolites. The liquid-liquid extraction procedure was applied for the enrichment of SCs.The pharmacological characterization of investigated SCs were studied by radioligand competition binding and ligand stimulated [35 S]GTPγS binding assays. For 5F-MDMB-PICA and 4F-MDMB-BICA, the median urinary concentrations were 0.076 and 0.312 ng/mL. For primary metabolites, the concentration range was 0.029-881.02* ng/mL for 5F-MDMB-PICA-COOH, and 0.396-4579* ng/mL for 4F-MDMB-BICA-COOH. In the polydrug aspect, the 22 urine samples were verified to be abused with 6 illicit drugs. The affinity of the metabolites to CB1R significantly decreased compared to the parent ligands. In the GTPγS functional assay, both 5F-MDMB-PICA and 4F-MDMB-BICA were acting as full agonists, while the metabolites were found as weak inverse agonists. Additionally, the G-protein stimulatory effects of the full agonist 5F-MDMB-PICA and 4F-MDMB-BICA were reduced by metabolites. These results strongly indicate the dose-dependent CB1R-mediated weak inverse agonist effects of the two butanoic acid metabolites. The obtained high concentration of main urinary metabolites of 5F-MDMB-PICA and 4F-MDMB-BICA confirmed the relevance of their routine analysis in forensic and toxicological practices. Based on in vitro binding assays, the metabolites presumably might cause a lower psychoactive effect than parent compounds.