Analytical study of photodegradation of inclusion complexes of nimodipine with alpha-, gamma-cyclodextrin, methyl-beta-cyclodextrin, and hydroxypropyl-beta-Cyclodextrin

The inclusion behavior of alpha-cyclodextrin (alpha-CD), gamma-cyclodextrin (gamma-CD), hydroxypropyl-beta-cyclodextrin (HP-betaCD), and methyl-beta-cyclodextrin (M-betaCD) with nimodipine (NM) in solution and in the solid state was investigated. Inclusion complexes of nimodipine with cyclodextrins (at a molar ratio of 1:1) in the solid state were obtained by the kneading method. Photochemical stability of NM in the solid inclusion complexes was assessed by IR spectrometry. The modified derivatives of beta-CD and alpha-CD were found to slow the photodegradation rate, whereas in the presence of gamma-CD the photodegradation of NM was a bit faster than in the corresponding physical mixture. Photochemical degradation of NM in liquid inclusion complexes was monitored by UV spectroscopy. According to the slowing effect on photodegradation of NM in the inclusion complexes, the studied cyclodextrins can be ordered as gamma-CD < alpha-CD < HP-betaCD < M-betaCD.