Characterization of in vitro metabolites of JWH-018, JWH-073 and their 4-methyl derivatives, markers of the abuse of these synthetic cannabinoids

•Optimization of a suitable extraction protocol for alkylindoles and their metabolites from biological fluids.•Detection of alkylindoles and their metabolites by means of the GC/MS method adopted by UNODC.•In vitro incubation with human liver microsomes of alkylindoles.•Study of the metabolism of 1-butyl-3-(1-(4-methyl)naphthoyl)indole for the first time.

In vitro incubation with human liver microsomes of JWH-018, JWH-073, JWH-122 and for the first time 1-butyl-3-(1-(4-methyl)naphthoyl)indole (the 4-methylnaphthoyl analogue of JWH-073) was investigated to identify the principal metabolites of alkylindole synthetic cannabinoids, thus helping the discovering of synthetic cannabinoids abusers. The results obtained showed that the most abundant metabolites were mono-hydroxylated derivatives either on the alkyl chain (ω or ω–1 position) or on the indole (presumably in position 5 or 6) and naphthalene moieties.Moreover the extraction conditions of these derivatives from biological fluids, mainly plasma and urine spiked with commercially available metabolite standards, and the incubation procedure were investigated to obtain a fast, reliable and suitable extraction protocol to detect either the parent drugs or their metabolites by means of GC/MS.