A 3D structural and conformational study of procyanidin dimers in water and hydro-alcoholic media as viewed by NMR and molecular modeling

The three‐dimensional structures of 5 procyanidin dimers have been determined in a hydro‐alcoholic medium and in water using 2D NMR and molecular mechanics. They are made from monomers of catechin (CAT) and epicatechin (EPI)‐B1: EPI‐CAT, B2: EPI–EPI, B3: CAT‐CAT, B4: CAT‐EPI and B2g: EPI‐EPI‐3‐O‐gal...

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Bibliographic Details
Published in:Magnetic resonance in chemistry 2006-09, Vol.44 (9), p.868-880
Main Authors: Tarascou, Isabelle, Barathieu, Karine, Simon, Cécile, Ducasse, Marie-Agnès, André, Yann, Fouquet, Eric, Dufourc, Erick J., de Freitas, Victor, Laguerre, Michel, Pianet, Isabelle
Format: Article
Language:English
Subjects:
3D structure
Alcohols - chemistry
Biflavonoids - chemistry
Catechin - chemistry
Chemical Sciences
Dimerization
Magnetic Resonance Spectroscopy
Models, Molecular
Molecular Conformation
molecular modeling
NMR
Proanthocyanidins - chemistry
procyanidin dimers
Tannins - chemistry
Water - chemistry
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Summary:The three‐dimensional structures of 5 procyanidin dimers have been determined in a hydro‐alcoholic medium and in water using 2D NMR and molecular mechanics. They are made from monomers of catechin (CAT) and epicatechin (EPI)‐B1: EPI‐CAT, B2: EPI–EPI, B3: CAT‐CAT, B4: CAT‐EPI and B2g: EPI‐EPI‐3‐O‐gallate. These tannins exist in two conformations that are in slow exchange in the NMR timescale (s), one is compact and the other extended. The compact form is found to dominate (76–98%) when the dimer is made of at least one CAT monomer (B1, B3, B4). Both forms are found in even proportions only in the case of procyanidin B2. The latter tannin can be converted into a dominant compact form when the lower EPI unit is galloylated. The finding of a predominant compact form for procyanidin dimers is discussed in relation with tannin‐saliva protein interactions that are of importance for the wine‐tasting/making processes. Copyright © 2006 John Wiley & Sons, Ltd.
ISSN:0749-1581
1097-458X
DOI:10.1002/mrc.1867