Rationalization and In Vitro Modeling of the Chemical Mechanisms of the Enzymatic Oxidation of Phenolic Compounds in Planta: From Flavonols and Stilbenoids to Lignins

Enzymatic oxidation of phenolic compounds is a widespread phenomenon in plants. It is responsible for the formation of many oligomers and polymers, which are generally described as the result of a combinatorial coupling of the different radicals formed through oxidation of the phenol group and deloc...

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Bibliographic Details
Published in:Chemistry : a European journal 2011-06, Vol.17 (26), p.7282-7287
Main Authors: Cottyn, Betty, Kollmann, Albert, Waffo-Teguo, Pierre, Ducrot, Paul-Henri
Format: Article
Language:English
Subjects:
Agricultural sciences
Chemistry
enzymes
Flavonols - chemistry
Flavonols - metabolism
Life Sciences
Lignin - chemistry
Lignin - metabolism
Models, Molecular
Molecular Structure
Oxidation
Oxidation-Reduction
Phenols - chemistry
Phenols - metabolism
Plants - chemistry
Plants - enzymology
Plants - metabolism
polymers
radical reactions
reaction mechanisms
Stereoisomerism
Stilbenes - chemistry
Stilbenes - metabolism
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Summary:Enzymatic oxidation of phenolic compounds is a widespread phenomenon in plants. It is responsible for the formation of many oligomers and polymers, which are generally described as the result of a combinatorial coupling of the different radicals formed through oxidation of the phenol group and delocalization of the radical. We focused our interest on several phenolic compounds that are present in plants and known to form, under enzymatic oxidation, oligomers with different type of linkages between monomers. To explain this diversity of inter‐monomer linkages and their variation according to the experimental procedure used for the enzymatic oxidation, we report an alternative mechanistic pathway involving dismutation of the radicals, leading to the formation of carbocations which, thereafter, react with nucleophilic species present in the medium. This alternative pathway allows the understanding of peculiar linkages between monomeric units in the oligomer and offers new insights for understanding the formation of phenolic biopolymers in plants. The possibility of dismutation of radicals generated through the enzymatic oxidation of plant vinyl phenols is proven and can be favoured according to the experimental procedure used (see scheme). This alternative pathway, leading to carbocations, allows the understanding of peculiar linkages between monomeric units in the oligomers and offers new insights for understanding the formation of phenolic biopolymers in plants.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201100421