Physicochemical and thermodynamic characterization of hydroxy pentacyclic triterpenoic acid/γ-cyclodextrin inclusion complexes

Hydroxy pentacyclic triterpenoic acids (HPTAs) have been described to exhibit numerous pharmacological properties. They also exhibit poor hydrosolubility, thus affecting their potential clinical interest. The association of these active substances with cyclodextrins could be employed to improve some properties such as bioavailability and activity. 1:1 Inclusion complexes of ursolic, oleanolic and betulinic acids with gamma-cyclodextrin were evaluated by DSC and H-1 NMR spectroscopy. The apparent formation constants (K-f) of the formed complexes were determined using RP-HPLC. Thermodynamic parameters Delta GA(0), Delta HA(0) and Delta SA(0) were calculated with temperatures ranging from 25 to 45 A degrees C to evaluate the complexation process. Finally the influence of gamma-CD on the HPTA water solubility was investigated by phase-solubility studies.