Going deeper into the toxicokinetics of synthetic cannabinoids: in vitro contribution of human carboxylesterases

Abstract

Synthetic cannabinoids (SC) are new psychoactive substances known to cause intoxications and fatalities. One reason may be the limited data available concerning the toxicokinetics of SC, but toxicity mechanisms are insufficiently understood so far. Human carboxylesterases (hCES) are widely known to play a crucial role in the catalytic hydrolysis of drugs (of abuse). The aim of this study was to investigate the in vitro contribution of hCES to the metabolism of the 13 SC 3,5-AB-5F-FUPPYCA, AB-5F-P7AICA, A-CHMINACA, DMBA-CHMINACA, MBA-CHMINACA, MDMB-4F-BINACA, MDMB-4en-PINACA, MDMB-FUBICA, MDMB-5F-PICA, MMB-CHMICA, MMB-4en-PICA, MMB-FUBINACA, and MPhP-5F-PICA. The SC were incubated with recombinant hCES1b, hCES1c, or hCES2 and analyzed by liquid chromatography–ion trap mass spectrometry to assess amide or ester hydrolysis in an initial activity screening. Enzyme kinetic studies were performed if sufficient hydrolysis was observed. No hydrolysis of the amide linker was observed using those experimental conditions. Except for MDMB-5F-PICA, ester hydrolysis was always detected if an ester group was present in the head group. In general, SC with a terminal ester bearing a small alcohol part and a larger acyl part showed higher affinity to hCES1 isozymes. Due to the low hydrolysis rates, enzyme kinetics could not be modeled for the SC with a tert-leucine-derived moiety, but hydrolysis reactions of MPhP-5F-PICA and of those containing a valine-derived moiety followed classic Michaelis–Menten kinetics. In conclusion, drug–drug/drug–food interactions or hCES polymorphisms may prolong the half-life of SC and the current results help to estimate the risk of toxicity in the future after combining them with activity and clinical data.

In vitro characterization of the pyrazole-carrying synthetic cannabinoid receptor agonist 5F-3,5-AB-PFUPPYCA and its structural analogs

“…Uchiyama et al and McLaughlin et al analyzed 3,5-AB-CHMFUPPYCA, the latter identifying the substance in a sample that was incorrectly advertised as 5F-5,3-AB-PFUPPYCA, while also showing the synthesis and characterization of the regioisomer 5,3-AB-CHMFUPPYCA [29,33] . Furthermore, metabolism of these compounds was investigated by Franz et al [34] , who also looked at their thermal stability, and more recently by Wagmann et al [35] .…”

In vitro metabolic fate of the synthetic cannabinoid receptor agonists (quinolin‐8‐yl 4‐methyl‐3‐(morpholine‐4‐sulfonyl)benzoate [QMMSB]) and (quinolin‐8‐yl 4‐methyl‐3‐((propan‐2‐yl)sulfamoyl)benzoate [QMiPSB]) including isozyme mapping and carboxylesterases activity testing

“…Previous studies revealed that the hydrolysis of the related SCRAs QMPSB, 2F‐QMPSB, BB‐22, PB‐22, and 5F‐PB‐22, which also have an 8‐hydroxyquinoline ester head group, was mainly catalyzed by hCES1 as well 12,13,25 . Furthermore, a study on SCRAs containing a methyl ester showed that mostly hCES1 catalyzed the hydrolysis 26 …”

“…12,13,25 Furthermore, a study on SCRAs containing a methyl ester showed that mostly hCES1 catalyzed the hydrolysis. 26 Incubations with pHLM and pHLS9 revealed a faster increase in the hydrolysis product than the control incubations indicating enzymatic ester hydrolysis as well. In both incubations, QMiPSB was almost completely degraded after 8 or 14 min, so no further ester hydrolysis was possible.…”