Binding Energy of Tea Catechin/Caffeine Complexes in Water Evaluated by Titration Experiments with¹H-NMR

Abstract

Evaluating the binding energy of a catechin/caffeine complex in water is important in order to elucidate the ability for molecular recognition of tea catechins. The results of this study revealed that the stoichiometric ratio of the complexation between tea chatechins (EGCg, ECg, EGC, and EC) and caffeine was 1:1 at least up to a concentration of 5.0 mM. The free energy (ÀÁG) values for binding in water at 301 K were evaluated to be 2.7, 2.6, 2.2, and 2.0 kcal/mol for EGCg, ECg, EGC, and EC, respectively, by the titration method with 1 H-NMR. An investigation of the 1 H-NMR chemical shift change and NOESY spectra in the catechin/caffeine solutions showed the participation of the A-rings of the catechins in complexation, as well as that of the galloyl groups or B-rings.

Chemical approach for target-selective degradation of oligosaccharides using photoactivatable organic molecules

“…After chemical synthesis of 19, its binding affinity with several monosaccharides, including octyl α-Glc (20), octyl β-Glc (21), octyl α-Gal (22), octyl β-Gal (23), and octyl α-Man (24), were examined, along with 1,6-hexanediol (25) (Fig. 9), using a 1 H-NMR binding assay based on the chemical shift of the imide NH proton of 19 in CDCl 3 [29][30][31][32]. It was found that the hybrid molecule 19 bound with high affinity to 21 (K a =539 M −1 ), in which all substituents were at equatorial orientations.…”

Properties of Precipitate of Creaming Down by (−)-Epigallocatechin-3-<i>O</i>-gallate and Caffeine

“…4) Thus, we investigated the crystal structure of the precipitate formed by creaming made from an aqueous solution of EGCg and caffeine, and detail properties of the complex of EGCg and caffeine in aqueous solution on the basis of the crystal structure of EGCg complex with caffeine.…”

Configurational Studies of Complexes of Various Tea Catechins and Caffeine in Crystal State

“…Also, it is very important to elucidate the stereochemical structures and the molecular interactions to explain the character and function of the complexes of catechins and caffeine. Previous structural studies of the complexes of polyphenols and caffeine were performed mainly in solution using several NMR techniques, [17][18][19] but their stereochemical structures and detailed intermolecular interactions have not been elucidated sufficiently.Thus, we have attempted to prepare crystals of the complexes of various tea catechins and caffeine, and investigated the stereochemical structures and intermolecular interaction using X-ray crystallographic analysis about the complexes which was able to get crystals successfully.A suspension of (Ϫ)-gallocatechin gallate (GCg) of galloylated catechin and caffeine in water gave two complexes, 1 : 2-and 2 : 2-complexes. X-Ray crystallographic analysis of crystals of the 1 : 2 complex showed that p-p interactions formed between the A, BЈ rings of GCg and the two sixmembered rings of caffeine, whereas the 2 : 2 complex showed that the A and C rings of GCg moieties faced each other, and face-to-face p-p interactions formed between the B ring of GCg and caffeine, the BЈ ring of GCg and caffeine.…”

“…Also, it is very important to elucidate the stereochemical structures and the molecular interactions to explain the character and function of the complexes of catechins and caffeine. Previous structural studies of the complexes of polyphenols and caffeine were performed mainly in solution using several NMR techniques, [17][18][19] but their stereochemical structures and detailed intermolecular interactions have not been elucidated sufficiently.…”