Preparation and characterization of inclusion complexes formed between baicalein and cyclodextrins

This study investigates the solubility of baicalein (Ba) with the addition of modified cyclodextrins using phase solubility method. The solubility of Ba in the presence of natural (alpha-,beta-, and gamma-) cyclodextrins and its derivatives, namely, hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and (2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD), was higher than that of free Ba. In particular, the stability constant of inclusion complex with DM-beta-CD was 13672.671 mol(-1), which was the highest among the examined cyclodextrins. The inclusion complexes of Ba and DM-beta-CD were prepared via freeze-drying method, which were both characterized in the solution and solid state by UV-vis spectroscopy, differential scanning calorimetry (DSC), proton nuclear magnetic resonance (H-1 NMR), scanning electron microscopy (SEM), and X-ray powder diffractometry (XRPD). The UV-vis, DSC, H-1 NMR, SEM, and XRPD results proved the formation of inclusion complex between Ba and DM-beta-CD. Furthermore, the dissolution rate and thermal stability of the inclusion complex were significantly enhanced compared with the pure drug. Therefore, using DM-beta-CD can effectively improve the solubility and thermal stability of free Ba, which is a promising approach to promote its clinical application. (C) 2013 Elsevier Ltd. All rights reserved.