Utility of cyclodextrins in the formulation of genistein: Part 1. Preparation and physicochemical properties of genistein complexes with native cyclodextrins

Isoflavones are suitable guest molecules for inclusion complex formation with cyclodextrins (CDs). The molecular encapsulation with CDs results in a solid, molecularly dispersed form and in a significantly improved aqueous solubility of isoflavones. Genistein, a key isoflavone constituent of Ononidis spinosae radix was found to form a supramolecular, non-covalent inclusion complex with both β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD), while it did not form a stable complex with α-CD. The guest genistein was found to spatially located in the less polar cavity of cyclodextrin. The isolated binary genistein/CD complexes appeared novel crystalline lattices. The in vitro dissolution of genistein entrapped into both β- and γ-CD, significantly surpassed that of the plain isoflavone.