Multiple complexation of cyclodextrin with soy isoflavones present in an enriched fraction

In the present study we evaluated the complexation of daidzein/genistein/glycitein, present in an isoflavone enriched fraction (IEF), with beta-cyclodextrin and 2-hydroxypropyl-beta-cyclodextrin (HP beta CD). Based on the increased solubility and higher complexation efficiency, IEF and HP beta CD solid complexes were prepared by kneading, freeze-drying, co-evaporation, spray-drying and microwave. The solid complexes were characterized using Fourier transformed-infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and nuclear magnetic resonance spectroscopy, and the isoflavone content and solubility were determined by liquid chromatography. The results suggest that the isoflavones daidzein, genistein and glycitein may be externally associated to HP beta CD as well as that isoflavones/HP beta CD inclusion complexes are formed through the insertion of B-ring into the cyclodextrin cavity. Except for the freeze-dried IEF/HP beta CD solid complex, all complexes showed similar content and solubility. In conclusion, the three isoflavones showed to be able to simultaneously complex with HP beta CD. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.