ABSTRACT
OBJECTIVE: To evaluate the effect of different cyclodextrins (ß-cyclodextrin [ß-CD], methyl-ß-cyclodextrin [Mß-CD], or hydroxypropyl-ß-cyclodextrin [HPß-CD]) and/or hydrophilic polymers (carboxymethylcellulose, hydroxypropylmethylcellulose [HPMC], polyethyleneglycol, or polyvinylpyrrolidone [PVP]) on daidzein solubility in water. MATERIALS AND METHODS: The corresponding associations were characterized in aqueous media using phase-solubility studies. The morphology of daidzein/cyclodextrin freeze-dried complexes was characterized using scanning electron microscopy, and their spatial configuration was proposed by means of nuclear magnetic resonance spectroscopy. RESULTS AND DISCUSSION: In the presence of 6 mM of cyclodextrins, the solubility of daidzein in water was significantly enhanced: 5.7-fold (ß-CD), 7.2-fold (Mß-CD), and 9.4-fold (HPß-CD). The analysis of the three solid complexes proved that the formation of inclusion complexes occurred through the insertion of the B and C rings of daidzein molecule into the cyclodextrins cavity. The association of daidzein/cyclodextrin complexes to the hydrophilic polymers HPMC or PVP (1%, w/w) was able to improve the solubility of daidzein even further. CONCLUSION: The highest solubilizing effect was obtained for daidzein/HPß-CD/PVP ternary system (12.7-fold).
