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

Abstract

Abstract Δ 8 ‐Tetrahydrocannabinol (Δ 8 ‐THC) as isomer of the well‐known Δ 9 ‐THC has a similar mode of action, and the potency was estimated to be two thirds compared with Δ 9 ‐THC. Content of Δ 8 ‐THC in plant material is low, but formulations containing Δ 8 ‐THC in high concentrations are gaining popularity. Δ 8 ‐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‐Δ 9 ‐tetrahydrocannabinol (Δ 9 ‐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 Δ 9 ‐THC‐COOH and the other one with higher intensity to the less common 11‐Nor‐9‐carboxy‐Δ 8 ‐Tetrahydrocannabinol (Δ 8 ‐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 Δ 8 ‐ and Δ 9 ‐THC‐COOH can be distinguished by chromatography and by fragmentation. Additional investigations of doping control samples containing Δ 9 ‐THC‐COOH revealed the simultaneous presence of Δ 8 ‐THC‐COOH in low concentrations (0.22–8.91 ng/ml) presumably due to plant origin. Percentage of Δ 8 ‐THC‐COOH varies from 0.05 to 2.83%. In vitro experiments using human liver microsomes showed that Δ 8 ‐THC is metabolized in the same way as Δ 9 ‐THC.

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