Activity-based detection of synthetic cannabinoid receptor agonists in plant materials

Since late 2019, fortification of 'regular' cannabis plant material with synthetic cannabinoid receptor agonists (SCRAs) has become a notable phenomenon on the drug market. As many SCRAs pose a higher health risk than genuine cannabis, recognizing SCRA-adulterated cannabis is important from a harm reduction perspective. However, this is not always an easy task as adulterated cannabis may only be distinguished from genuine cannabis by dedicated, often expensive and time-consuming analytical techniques. In addition, the dynamic nature of the SCRA market renders identification of fortified samples a challenging task. Therefore, we established and applied an in vitro cannabinoid receptor 1 (CB₁) activity-based procedure to screen plant material for the presence of SCRAs.

The assay principle relies on the functional complementation of a split-nanoluciferase following recruitment of β-arrestin 2 to activated CB₁. A straightforward sample preparation, encompassing methanolic extraction and dilution, was optimized for plant matrices, including cannabis, spiked with 5 µg/mg of the SCRA CP55,940.

The bioassay successfully detected all samples of a set (n = 24) of analytically confirmed authentic Spice products, additionally providing relevant information on the 'strength' of a preparation and whether different samples may have originated from separate batches or possibly the same production batch. Finally, the methodology was applied to assess the occurrence of SCRA adulteration in a large set (n = 252) of herbal materials collected at an international dance festival. This did not reveal any positives, i.e. there were no samples that yielded a relevant CB₁ activation.

In summary, we established SCRA screening of herbal materials as a new application for the activity-based CB₁ bioassay. The simplicity of the sample preparation, the rapid results and the universal character of the bioassay render it an effective and future-proof tool for evaluating herbal materials for the presence of SCRAs, which is relevant in the context of harm reduction.