alpha-cyclodextrin and thiobarbituric-acid

Quantitative structure-stability relationships (QSSRs) are formulated for the inclusion complexation of 17 barbituric acid derivatives with alpha- and beta-cyclodextrin. The variation in the complex stability constants K alpha and K beta is found to be partly accounted for by the molar refractivity or the hydrophobicity of the substituent R1 at position 5 of the barbiturate ring. In addition, K alpha also depends upon whether or not R1 is branching or cyclic, and K beta also depends upon whether the guest molecule is a barbiturate or a thiobarbiturate. The results suggest that in alpha-cyclodextrin-barbiturate complexes the cyclodextrin cavity includes only R1, while in beta-cyclodextrin complexes both R1 and (part of) the barbiturate ring are included. This complexation model is compared with those proposed by other authors.

Topics: alpha-Cyclodextrins; Barbiturates; beta-Cyclodextrins; Chemistry, Pharmaceutical; Chromatography, High Pressure Liquid; Cyclodextrins; Dextrins; Drug Stability; Kinetics; Solubility; Starch; Structure-Activity Relationship; Thiobarbiturates