Calorimetric study of the complex formation of cyclodextrins with nicotinic and niflumic acids in aqueous solutions

Abstract

Thermodynamic parameters of the inclusion complex formation of native and hydroxypropylated cyclodextrins with pharmacologically active niflumic and nicotinic acids were obtained and analyzed. It was shown that cyclodextrins selectively react with these acids and display a higher binding affinity to niflumic acid which is more hydrophobic and less hydrated compared to nicotinic acid. An influence of the cyclodextrin cavity size and accessibility of the hydroxypropyl substituent on the thermodynamics of the reactions and the binding mode of the acids was revealed and discussed in this work.