title: 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 X-ray 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.
authors.affiliation: Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima, Japan. ishizu@fupharm.fukuyama-u.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Ishizu
authors.forename: Shinya
authors.initials: S
authors.lastname: Kajitani
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsutsumi
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.forename: Hideji
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Chikako
authors.initials: C
authors.lastname: Hirata
mesh_terms: D002110:Caffeine / Q000737:chemistry*; D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003505:Cyclodextrins / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D013237:Stereoisomerism; D013662:Tea / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D003505:Cyclodextrins; D013662:Tea; D014867:Water; D002110:Caffeine; D002392:Catechin; C045651:epigallocatechin gallate