Competition between (+)-Catechin and (−)-Epicatechin in Acetaldehyde-Induced Polymerization of Flavanols

• Published in: Journal of agricultural and food chemistry Vol. 47; no. 5; pp. 2088 - 2095
• Main Authors: Es-Safi, Nour-Eddine, Fulcrand, Hélène, Cheynier, Véronique, Moutounet, Michel
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.05.1999
• Subjects: Acetaldehyde; acidity; Biological and medical sciences; catechin; Catechin - chemistry; chemical reactions; chemical structure; condensation reactions; epicatechin; Fermented food industries; Flavonoids - chemistry; Food engineering; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; Hydrogen-Ion Concentration; Kinetics; Life Sciences; Miscellaneous; Models, Chemical; polymerization; Stereoisomerism; Wines and vinegars; Flavanol; Catechin; Biochemical analysis; Thiolysis; HPLC chromatography; Polymerization; Competitive reaction; Model study; Experimental study; Red wine; Condensation; Chemical reaction kinetics; Acetaldehyde; Organic pigment; Polyphenol; Phenols; pH; Comparative study; Vegetal tannin
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf980628h

The reactions of (+)-catechin and (−)-epicatechin in the presence of acetaldehyde were studied in model solution systems. When incubated separately with acetaldehyde and at pH values varying from 2.2 to 4.0, reactions were faster with (−)-epicatechin than with (+)-catechin. In mixtures containing both (+)-catechin and (−)-epicatechin with acetaldehyde, new compounds besides the homogeneous bridged derivatives were detected. These compounds were concluded to be hetero-oligomers consisting of (+)-catechin and (−)-epicatechin linked with an ethyl bridge. In this case, the reaction of (−)-epicatechin was faster than that of (+)-catechin. This was also observed in solutions containing the two flavanols and the (+)-catechin−ethanol intermediate. Under these conditions, the homogeneous (+)-catechin bridged dimers and heterogeneous dimers were obtained by action of the intermediate on (+)-catechin and (−)-epicatechin, respectively. In addition, the homogeneous (−)-epicatechin ethyl-bridged dimers were also detected, showing that ethyl linkages underwent depolymerization and recombination reactions. Keywords: (+)-Catechin; (−)-epicatechin; acetaldehyde; condensation; thiolysis; LC/DAD; LC/MS; competitive action