2-Hydroxypropyl-β-cyclodextrin (HP-β-CD) is a cyclic oligosaccharide containing seven D-(+)-glucopyranose units that is widely used to improve the aqueous solubility of various compounds, especially those containing a phenyl group. The circular arrangement of its glucose units produces a torus-shaped ring configuration in which the CH2 groups and ether linkages of the molecule face the hollow interior, resulting in a nonpolar, hydrophobic cavity and a polar, hydrophilic exterior. When combined in solution with other compounds, the nonpolar aromatic portions of that compound interact with the nonpolar interior of the HP-β-CD molecule, thus isolating the aromatic portion of the molecule from the water and thereby increasing its aqueous solubility.
