Study of freeze-dried quercetin-cyclodextrin binary systems by DSC, FT-IR, X-ray diffraction and SEM analysis.

The inclusion behavior of 2-hydroxypropyl beta-cyclodextrin (HPbetaCD) and beta-cyclodextrin (betaCD), in solution and solid-state was studied towards a poorly water-soluble bioflavonoid, quercetin (QURC), chemically 3,3',4',5',7-pentahydroxy flavone. Drug-cyclodextrin solid systems were prepared by freeze-drying. Phase solubility study was used to evaluate the complexation in solution, of two cyclodextrins, i.e., betaCD and HPbetaCD. The stoichiometry and stability constants of QURC-betaCD (1:1 and 402M(-1)) and QURC-HPbetaCD (1:1 and 532M(-1)) complexes were calculated by phase solubility method. The formation of inclusion complexes with betaCD and HPbetaCD in the solid-state were confirmed by infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy (SEM).