Structual Features of Inclusion Complexes between Glycyrrhizinates and Cyclodextrins

Abstract

Inclusion complexations of α- and β-glycyrrhizinate (α-GK2 and β-GK2) or β-GK2 methyl ester (GMe) with y-cyclodextrin (γ-CyD) and 2, 6-di-O-methylcyclodextrin (DM-β-CyD) have been structurally investigated by ultraviolet (UV) and circular dichroism (CD) spectroscopy. Based on a close relationship between the UV-absorption wavelength or the CD-intensity and the polarity of the local microenvironment around the enone moiety in the triterpenoidal part, it is found that β-GK2 forms only 1: 1 complexes with γ-CyD and DM-β-CyD, while GMe and α-GK2 form quite a stable 1:1 complex with γ-CyD, accompanied by weak complexation with a 1: 2 stoichio-metry. The location of the CyD torus on the triterpenoidal skeleton is determined with the help of force field molecular mechanics calculations.