Simple Method Development for the Separation of Chiral Synthetic Cannabinoids using Ultra High Performance Supercritical Fluid Chromatography

by Jacquelyn Runco, Andrew Aubin, Jo-Ann Jablonski Waters Corporation, Milford, MA, USA

Ultra high performance supercritical fluid chromatography (UHPSFC) technology presents an alternative and orthogonal solution to GC and HPLC for the separation of synthetic cannabinoids. In particular, it offers excellent selectivity for structural analogs and stereoisomers. Here, a simple method development strategy is demonstrated for the chiral analysis of selected synthetic cannabinoids including: HU-210, HU- 211, (±)-CP 47,497, (±)-epi CP 47,497, (±)-CP 55,940 and (±)5-epi CP 55,940. Fast stereoisomeric separations, including related enantiomers and diastereomers, are achieved on the Waters ACQUITY UPC2

System using the Waters Trefoil chiral columns. The efficiency of UHPSFC is demonstrated for rapid enantiomeric separation of chiral synthetic cannabinoids.

Synthetic cannabinoids (so named because they are structurally related to naturally occurring compounds found in the marijuana plant) refer to a large and growing number of man-made compounds that are often sprayed on dried, shredded plant material so they can be smoked. Mixtures of synthetic cannabinoids are sold under various brand names such as ‘Spice’ and ‘Smoke’ and are becoming more widely used as illicit, abused drugs [1]. Many of these analogues are being produced in order to circumvent laws banning their use as recreational drugs [2]. However, some synthetic cannabinoids have been used for medicinal purposes including rimonabant, nabilone, and dronabinol [3]. In addition, efforts have been ongoing to find selective analogues of tetrahydrocannabinol (THC) that separate beneficial effects, such as pain treatment, from psychotropic effects [4]. Since pharmacological studies involving structure–activity relationships, receptor binding, and detailed mechanisms of activity for these drugs is required, it is necessary to fully characterise these molecules.

The series of synthetic cannabinoids possess a wide structural variability and potent cannabimimetic pharmacological activity, and bind to the same cannabinoid receptors as THC. The modifications made to these compounds result in structural analogues, structural homologues, positional isomers and stereoisomers [1,4]. Just as with other active pharmaceutical ingredients, stereochemistry of synthetic cannabinoids affects pharmacological activity. For example, HU-210 is a synthetic cannabinoid

that has neuroprotective effects and psycho activity 100 to 800x more potent than THC, while HU-211 (the enantiomer of HU-210) also has slightly different neuroprotective effects without the psychotropic effects.

Due to the growing popularity and hazardous potential of uncharacterised synthetic cannabinoids, the ingredient analysis of these products is required in forensic toxicology, regulatory environments, and pharmaceutical development [1]. Specifically, chiral separation of the cannabinoid stereoisomers is important for pharmaceutical development, whether for identification and characterization of impurities, or for purification purposes. Chiral analysis is also important for screening in forensic laboratories, where achiral analysis

alone will not result in comprehensive qualitative analysis. A variety of analytical techniques have been used for the comprehensive screening of drugs of abuse, including immunoassay, GC-MS and LC-MS. The immunoassay solution suffers from low selectivity, while GC is limited to volatile compounds and requires derivatisation [1]. LC-MS offers high sensitivity and specificity for cannabinoids, however, another complementary methodology is needed to obtain high-precision, qualitative analysis of these products. As laboratories struggle to keep pace with the proliferation of these newly emerging drugs, simple method development strategies that can be quickly applied to obtain the necessary qualitative information are urgently needed [2].

Figure 1: Stereochemical structures of selected synthetic cannabinoids

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