INCLUSION OF NONSTEROIDAL ANTIINFLAMMATORY AGENTS INTO AQUEOUS CYCLODEXTRINS - A UV-ABSORPTION SPECTROSCOPIC STUDY

Uv-absorption spectroscopy technique enables the determination of the binding constants of some non-steroidal anti-inflammatory drugs to alp ha-, beta-, and gamma-cyclodextrins. In all cases the stoichiometry of the complex is 1:1 and the drugs have a higher affinity for beta-cycl odextrin than for alpha-cyclodextrin or gamma-cyclodextrin. The dielec tric constant of the cyclodextrin cavity has also been determined. The values show that the microenvironment of the drugs in beta-cyclodextr in is more hydrophobic than the corresponding value for alpha-cyclodex trin and for gamma-cyclodextrin. This fact seems to be due to a greate r penetration of the drugs into the beta-cyclodextrin cavity. From the changes observed in the C-band of the absorption spectra of the compl exed drug, the changes in the structure of the drug included into the cyclodextrin may be analyzed and compared to the structure of the free drug.