H-1 NMR, UV and circular dichroism study of inclusion complex formation between the 5-lipoxygenase inhibitor zileuton and beta- and gamma-cyclodextrins

The interactions between the chiral 5-lipoxygenase inhibitor zileuton and b eta- and gamma-cyclodextrins were characterised through solubility measurem ents and H-1 NMR, UV and circular dichroism spectroscopic studies. gamma-Cy clodextrin was found to increase the solubility of racemic zileuton while t he complexes formed with beta-cyclodextrin were almost insoluble. The chira l recognition mechanism which comes into play between the cyclodextrins and the zileuton isomers was studied by H-1 NMR, UV, and CD spectroscopies. Th e apparent association constants for the inclusion complexes were obtained from the changes in chemical shifts, UV absorbance and ellipticity, respect ively. It was found that zileuton interacted more strongly with beta-cyclod extrin, while gamma-cyclodextrin was a better chiral selector. The geometri es of the different complexes were also postulated on the basis of 2D NMR R OESY experiments.