Emergence of the less common cannabinoid Δ⁸ -Tetrahydrocannabinol in a doping sample

Δ⁸ -Tetrahydrocannabinol (Δ⁸ -THC) as isomer of the well-known Δ⁹ -THC has a similar mode of action, and the potency was estimated to be two thirds compared with Δ⁹ -THC. Content of Δ⁸ -THC in plant material is low, but formulations containing Δ⁸ -THC in high concentrations are gaining popularity. Δ⁸ -THC is to be regarded as prohibited substance according to the Prohibited List of the World Anti-Doping Agency (WADA). Contradictory results between initial testing procedure and confirmatory quantitation for 11-Nor-9-carboxy-Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC-COOH) of a doping control sample gave rise for follow-up testing procedures. After alkaline hydrolysis and liquid-liquid extraction, the sample was analyzed by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) using isocratic elution instead of gradient elution, which is used for standard procedure. Isocratic elution resulted in two peaks instead of one using gradient elution. Both peaks showed same fragmentation. Using certified reference materials, one peak could be assigned to Δ⁹ -THC-COOH and the other one with higher intensity to the less common 11-Nor-9-carboxy-Δ⁸ -Tetrahydrocannabinol (Δ⁸ -THC-COOH) in a concentration of approximately 1200 ng/ml. As complementary method, gas chromatography tandem mass spectrometry (GC-MS/MS) can also be used for identification. Here Δ⁸ - and Δ⁹ -THC-COOH can be distinguished by chromatography and by fragmentation. Additional investigations of doping control samples containing Δ⁹ -THC-COOH revealed the simultaneous presence of Δ⁸ -THC-COOH in low concentrations (0.22-8.91 ng/ml) presumably due to plant origin. Percentage of Δ⁸ -THC-COOH varies from 0.05 to 2.83%. In vitro experiments using human liver microsomes showed that Δ⁸ -THC is metabolized in the same way as Δ⁹ -THC.