Inclusion of non-steroidal anti-inflammatory agents into aqueous cyclodextrins: A UV-absorption spectroscopic study

Abstract

[EN]UV-absorption spectroscopy technique enables the determination of the binding constants of some non-steroidal anti-inflammatory drugs to α-, β-, and γ-cyclodextrins. In all cases the stoichiometry of the complex is 1:1 and the drugs have a higher affinity for β-cyclodextrin than for α-cyclodextrin or γ-cyclodextrin. The dielectric constant of the cyclodextrin cavity has also been determined. The values show that the microenvironment of the drugs in β-cyclodextrin is more hydrophobic than the corresponding value for α-cyclodextrin and for γ-cyclodextrin. This fact seems to be due to a greater penetration of the drugs into the β-cyclodextrin cavity. From the changes observed in the C-band of the absorption spectra of the complexed 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.