Configurational studies of complexes of tea catechins with caffeine and various cyclodextrins

Abstract

A suspension of an equimolecular amount of ent-gallocatechin-3-O-gallate (entGCg) and caffeine in water afforded two kinds of crystals, which were 1:2 and 2:2 complexes of entGCg and caffeine. The stereochemical structures and intermolecular interactions between entGCg and caffeine were determined by Xray crystallographic analysis. The crystal structure of entGCg was determined and compared with those of the 1:2 and 2:2 complexes. Epigallocatechin-3-O-gallate (EGCg) formed a 1:1 complex with β-cyclodextrin (CD), in which the aromatic A ring and a part of the heterocyclic C ring were included from the wide secondary hydroxyl group side of the β-CD cavity in aqueous solution, while the B rings and 3-O-gallate groups (B' rings) were left outside the cavity. In contrast, entGCg formed a 1:2 complex with β-CD, in which the aromatic A and B rings of entGCg were included by two molecules of β-CD. © Georg Thieme Verlag KG Stuttgart - New York.