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

Abstract

In Cannabis sativa, Δ9-Tetrahydrocannabinolic acid-A (Δ9-THCA-A) is the non-psychoactive precursor of Δ9- tetrahydrocannabinol (Δ9-THC). In fresh plant material, about 90% of the total Δ9-THC is available as Δ9-THCA-A. When heated (smoked or baked), Δ9-THCA-A is only partially converted to Δ9-THC and therefore, Δ9-THCA-A can be detected in serum and urine of cannabis consumers. The aim of the presented study was to identify the metabolites of Δ9-THCA-A and to examineparticularlywhether oral intake of Δ9-THCA-A leads toin vivo formation of Δ9-THC ina ratmodel.After oral application of pure Δ9-THCA-A to rats (15mg/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 Δ9-THC and its metabolites, urine extracts were analyzed by gas chromatography-mass spectrometry (GC-MS). The identified metabolites show that Δ9-THCA-A undergoes a hydroxylation in position 11 to 11-hydroxy-Δ9- tetrahydrocannabinolic acid-A (11-OH-Δ9-THCA-A), which is further oxidized via the intermediate aldehyde 11-oxo-Δ9-THCA-A to 11-nor-9-carboxy- Δ9-tetrahydrocannabinolic acid-A (Δ9-THCA-A-COOH). Glucuronides of the parent compound and both main metabolites were identified in the rat urine as well. Furthermore, Δ9-THCA-A undergoes hydroxylation in position 8 to 8-alpha- and 8-betahydroxy-Δ9-tetrahydrocannabinolic acid-A, respectively, (8α-Hydroxy-Δ9-THCA-A and 8β-Hydroxy-Δ9-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 Δ9-THCA-A to Δ9-THCwas not observed. Copyright © 2009 John Wiley & Sons, Ltd.