INTERACTION OF SOME BARBITURIC-ACID DERIVATIVES WITH HYDROXYPROPYL-BETA-CYCLODEXTRIN

The interaction between 39 barbituric acid derivatives and hydroxypropyl-beta-cyclodextrin (HPbetaCD) was studied by reversed-phase charge-transfer thin-layer chromatography. Except for one derivative, each barbiturate formed inclusion complexes with HPbetaCD, the complex always being more hydrophilic than the uncomplexed drug. The intensity of interaction significantly increased with increasing lipophilicity of the guest molecule proving the preponderant role of hydrophobic interactions in inclusion complex formation. The di- and trisubstituted derivatives probably formed complexes of different stoichiometry. Free-Wilson analysis proved that the intensity of interaction increases with increasing size of the substituents at least in the studied range.