Studies on the metabolism of the Δ9-tetrahydrocannabinol precursor Δ9-tetrahydrocannabinolic acid A (Δ9-THCA-A) in rat using LC-MS/MS, LC-QTOF MS and GC-MS techniques

In Cannabis sativa, Delta 9-Tetrahydrocannabinolic acid-A (Delta 9-THCA-A) is the non-psychoactive precursor of Delta 9-tetrahydrocannabinol (Delta 9-THC). In fresh plant material, about 90% of the total Delta 9-THC is available as Delta 9-THCA-A. When heated (smoked or baked), Delta 9-THCA-A is only partially converted to Delta 9-THC and therefore, Delta 9-THCA-A can be detected in serum and urine of cannabis consumers. The aim of the presented study was to identify the metabolites of Delta 9-THCA-A and to examine particularly whether oral intake of Delta 9-THCA-A leads to in vivo formation of Delta 9-THC in a rat model. After oral application of pure Delta 9-THCA-A to rats (15 mg/kg body mass), urine samples were collected and metabolites were isolated and identified by liquid chromatography-mass spectrometry (LC-MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high resolution LC-MS using time of flight-mass spectrometry (TOF-MS) for accurate mass measurement. For detection of Delta 9-THC and its metabolites, urine extracts were analyzed by gas chromatography-mass spectrometry (GC-MS). The identified metabolites show that Delta 9-THCA-A undergoes a hydroxylation in position 11 to 11-hydroxy-Delta 9-tetrahydrocannabinolic acid-A (11-OH-Delta 9-THCA-A), which is further oxidized via the intermediate aldehyde 11-oxo-Delta 9-THCA-A to 11-nor-9-carboxy-Delta 9-tetrahydrocannabinolic acid-A (Delta 9-THCA-A-COOH). Glucuronides of the parent compound and both main metabolites were identified in the rat urine as well. Furthermore, Delta 9-THCA-A undergoes hydroxylation in position 8 to 8-alpha- and 8-beta-hydroxy-Delta 9-tetrahydrocannabinolic acid-A, respectively, (8 alpha-Hydroxy-Delta 9-THCA-A and 8 beta-Hydroxy-Delta 9-THCA-A, respectively) followed by dehydration. Both monohydroxylated metabolites were further oxidized to their bishydroxylated forms. Several glucuronidation conjugates of these metabolites were identified. In vivo conversion of Delta 9-THCA-A to Delta 9-THC was not observed. Copyright (C) 2009 John Wiley & Sons, Ltd.