Conversion of cannabidiol to Δ9-tetrahydrocannabinol and related cannabinoids in artificial gastric juice, and their pharmacological effects in mice


Cannabidiol (CBD), a nonpsychoactive cannabinoid, was found to be converted to 9α-hydroxyhexahydrocannabinol (9α-OH-HHC) and 8-hydroxy-iso-hexahydrocannabinol (8-OH-iso-HHC) together with Δ9-tetrahydrocannabinol (Δ9-THC), a psychoactive cannabinoid, and cannabinol in artificial gastric juice. These cannabinoids were identified by gas chromatography-mass spectrometry (GC-MS) by comparison with the spectral data of the authentic compounds. Pharmacological effects of 9α-OH-HHC and 8-OH-iso-HHC in mice were examined using catalepsy, hypothermia, pentobarbital-induced sleep prolongation, and antinociception against acetic acid-induced writhing as indices. The ED50 values (effective dose producing a 50% reduction of control; mg/kg, i.v.) of 9α-OH-HHC and 8-OH-iso-HHC for the cataleptogenic effect were 8.0 and 30.4, respectively. 8-OH-iso-HHC (10 mg/kg, i.v.) produced a significant hypothermia from 15 to 90 min after administration, although 9α-OH-HHC failed to induce such an effect at the same dose. However, both HHCs (10 mg/kg, i.v.) significantly prolonged pentobarbital-induced sleeping time by 1.8 to 8.0 times as compared with the control solution with 1% Tween 80-saline. The ED50 values (mg/kg, i.v.) of 9α-OH-HHC and 8-OH-iso-HHC for the antinociceptive effect were 14.1 and 39.4, respectively. The present study demonstrated that CBD can be converted to Δ9-THC and its related cannabinoids, 9α-OH-HHC and 8-OH-iso-HHC, in artificial gastric juice, and that these HHCs show Δ9-THC-like effects in mice, although their pharmacological effects were less potent than those of Δ9-THC.

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Correspondence to Kazuhito Watanabe.

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Watanabe, K., Itokawa, Y., Yamaori, S. et al. Conversion of cannabidiol to Δ9-tetrahydrocannabinol and related cannabinoids in artificial gastric juice, and their pharmacological effects in mice. Forensic Toxicol 25, 16–21 (2007).

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  • Cannabidiol
  • Δ9-Tetrahydrocannabinol
  • 9α-Hydroxyhexahydrocannabinol
  • 8-Hydroxy-iso-hexahydrocannabinol
  • Acid-catalyzed cyclization
  • Antinociceptive effect