Δ9-Tetrahydrocannabinol hemisuccinate (THC-HS), an ester prodrug of Δ9-tetrahydrocannabinol (THC) has been investigated for its potential to form inclusion complexes with modified synthetic beta-cyclodextrins
(CDs). Phase solubility studies were performed to determine the stoichiometric ratio of complexation of THC-HS with random
methylated beta-cyclodextrin (RAMEB) and 2-hydroxypropyl beta-cyclodextrin (HPBCD). THC-HS/RAMEB and THC-HS/HPBCD solid systems
were prepared by lyophilization and the lyophilized complexes were characterized by Fourier transform infrared (FT-IR) spectroscopy,
proton nuclear magnetic spectroscopy, and molecular modeling techniques. The formation of inclusion complexes of THC-HS/RAMEB
and THC-HS/HPBCD was demonstrated by an AL type curve with the slopes less than unity by the phase solubility method. The association constants for THC-HS/RAMEB and
THC-HS/HPBCD were found to be 562.48 and 238.83 M−1, respectively. The stoichiometry of both of the complexes was found to be 1:1 as determined from the Job's plot. This was
confirmed by 1H NMR and FT-IR techniques. The results obtained from the molecular modeling studies were in accordance with the data obtained
from nuclear magnetic resonance and FT-IR. The docking studies revealed the most probable mode of binding of THC-HS with RAMEB
in which the alkyl chain was submerged in the hydrophobic pocket of the CD molecule and hydrogen bonding interactions were
observed between the hemisuccinate ester side chain of THC-HS and the rim hydroxy groups of RAMEB. The solubility of THC-HS
was significantly higher in RAMEB compared to HPBCD. Solid dispersions of THC-HS with CDs will be further utilized to develop
oral formulations of THC-HS with enhanced bioavailability.
Key words Δ9-tetrahydrocannabinol hemisuccinate - job's plot - lyophilization - molecular modeling - random methylated beta-cyclodextrin
Guest Editors: Michael Repka, Joseph Reo, Linda Felton, and Stephen Howard