Calculation study on complex formation of catechins with β-cyclodextrin using density function theory

• Published in: Journal of inclusion phenomena and macrocyclic chemistry 2021-06, Vol.100 (1-2), p.99-107
• Main Authors: Ikeda, Hirohito, Ohata, Tomonori, Yukawa, Miho, Tsutsumi, Hiroyuki, Fujisawa, Masao, Aki, Hatsumi
• Format: Article
• Language: English
• Subjects: Bitterness; Catechin; Chemistry; Chemistry and Materials Science; Complex formation; Crystallography and Scattering Methods; Cyclodextrins; Density functional theory; Food Science; Free energy; Heat of formation; Hydrogen bonds; Inclusion complexes; Organic Chemistry; Original Article
• ISSN: 1388-3127; 1573-1111
• DOI: 10.1007/s10847-021-01057-7

The inclusion of catechins with cyclodextrin (CD) is performed for the purpose of improving the water solubility and reducing the bitterness of catechins. In this study, the effect of catechins’ conformation on the formation of an inclusion complex between catechins and β-CD was examined by density functional theory (DFT) calculation at the B3PW91/cc-pVDZ level. It is known that the main components of catechins in tea leaves are (−)-epigallocatechin (EGC), which is a non-gallate-type catechin, and (−)-epigallocatechin gallate (EGCg), which is a gallate-type catechin. Catechins have a plurality of sites that can be included by β-CD (EGC: AC ring and B ring, EGCg: AC ring, B ring, and B′ ring). First, initial models for the calculation in which each ring of catechins gradually approaches into the cavity of β-CD were built. These initial models were optimized in water and then the optimized structure of the inclusion complex in water was determined. From the results of calculation, the degree of penetration of each ring into the β-CD cavity, the complex formation energy, and the number of intermolecular hydrogen bonds were examined. The results of calculation showed that the AC ring of catechins is most deeply included in the β-CD cavity and the B′ ring of catechins forms an energetically stable complex with β-CD. It was found that the inclusion complex of catechins and β-CD is stabilized energetically by intermolecular hydrogen bonds.