New Polymorph of β-Cyclodextrin with a Higher Bioavailability

Abstract

A new polymorph of anhydrous β-cyclodextrin (polymorph III) was obtained and characterized for the first time using powder X-ray diffraction, infrared spectroscopy and thermal analysis. Solution enthalpy and time of dissolution in water were determined by solution calorimetry for this polymorph and compared with those of dried commercial form of β-cyclodextrin (polymorph I), its amorphous form and 2-hydroxypropyl-β-cyclodextrin. Specific heat capacity of polymorphs I and III was determined by differential scanning calorimetry in the wide range of temperatures, which gives enthalpy and Gibbs energy of polymorphic transition at 298 K. Affinity of polymorph III and 2-hydroxypropyl-β-cyclodextrin for water was characterized by determination of their hydration isotherms, which gives the values of hydration Gibbs energy. Being energy-rich, the found new polymorph of β-cyclodextrin has a significantly higher dissolution rate and an in-creased affinity for water compared with the dried commercial form of β-cyclodextrin. Such properties make the new polymorph promising in industrial applications for guest inclusion in aqueous solutions and pastes and may be a desirable alternative for water-soluble β-cyclodextrin derivatives.