Spectroscopic Study of the Inclusion Complexes of Phenylbutazone and Oxyphenbutazone with Cyclodextrins in Polar Reaction Media

Abstract

The formation of inclusion complexes of α-, β-, hydroxypropyl-β- (HP-β-) and γ-cyclodextrins with phenylbutazone and oxyphenbutazone has been studied in aqueous buffer solution (pH 7.5 and 0.1 mol dm-3 NaCl), dimethylsulfoxide, and 25, 50 and 75% dimethylsulfoxide/water mixtures. These complexation reactions have been followed by UV electronic absorption spectroscopy. In addition, 1D and 2D 1H NMR spectra were recorded to obtain structural information about the inclusion complexes formed in solution; 136 binding constant values were determined at five different temperatures (288, 293, 298, 303 and 310 K) from the electronic absorption data and, from these Δ Hbinding and Δ Sbinding values were obtained. At the studied cyclodextrin and guest concentration ranges, 1 : 1 inclusion complexes were detected. Only in three cases were 1 : 2 complexes detected, those of phenylbutazone and oxyphenbutazone with α-cyclodextrin in aqueous, and oxyphenbutazone with hydroxypropyl-β-cyclodextrin in 75% dimethylsulfoxide/water solutions.