Inclusion complexations of clomipramine HCl (CIP), a tricyclic antidepressant, with β-cyclodextrin (β-CyD) and heptakis (2, 6-di-O-methyl) -β-CyD (DM-β-CyD) were studied by ultraviolet, fluorescence, circular dichroism and 13C-nuclear magnetic resonance spectroscopies. Both β-CyDs decelerated the photodegradation of CIP under aerobic and anaerobic conditions, where the inhibitory effect of DM-β-CyD was larger than that of β-CyD. The photodegradation products of CIP in the absence and presence of DM-β-CyD were analyzed by liquid chromatography/mass spectroscopy. The results indicate that β-CyDs suppress the formation of 3-hydroxyimipramine, while they accelerate the formation of imipramine. The alternation in photochemical reaction of CIP may result from the inclusion of chlorobenzene moiety of CIP molecule within the hydrophobic cavity of β-CyDs.
