Study of interaction of spironolactone with hydroxypropyl-β-cyclodextrin in aqueous solution and in solid state

The interaction between spironolactone (Sp) and hydroxypropyl-β-cyclodextrin (HPβCD) has been investigated in aqueous solution and in the solid state. Phase solubility studies indicate that the complex is formed with possible stoichiometry of 1:1 and association constant of 9806 M−1. Differential scanning calorimetry (DSC) gave evidence for the formation of the complex. The details of Sp/HPβCD molecular interaction were analyzed by Fourier transform infrared (FTIR) and Raman spectroscopy. The characterization studies confirmed that the CO groups of the six-member ring and acetylthio group of Sp interacts with the hydroxyl groups inside and outside the cavity of HPβCD through formation of hydrogen bonds.