Structural Features of the β-CD Complexes with Naringin and its Dihydrochalcone and Aglycon Derivatives by 1 H NMR

Abstract

The β-CD inclusion complexes of naringin 1, naringin dihydrochalcone 2 and the aglycon of naringin dihydrochalcone 3 have been investigated by 1H NMR spectroscopy. Continuous variation plots show the stoichiometry of all complexes to be 1 : 1. Thestructure of complexes was determined from 2D ROESY and 1D ROE experiments. For 1 and 2 the inclusion involves the aromatic rings leaving the disaccharide unit α-L-Rha-(1-2)-β-D-Glc outside the β-CD cavity. For naringin 1 the inclusion occurs preferentially from the wider rim of the β-CD truncated cone with the terminal phenolic ring deeply inserted into the β-CD cavity while for naringin dihydrochalcon 2 it occurs from the side of the β-CD narrower rim. The β-CD/aglycon 3 complex exists as an equilibrium of the two inclusion modes.