H/D Exchange Processes in Flavonoids: Kinetics and Mechanistic Investigations

Several classes of flavonoids, such as anthocyanins, flavonols, flavanols, and flavones, undergo a slow H/D exchange on aromatic ring A, leading to full deuteration at positions C(6) and C(8). Within the flavanol class, H-C(6) and H-C(8) of catechin and epicatechin are slowly exchanged in D2O to the...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2021-06, Vol.26 (12), p.3544
Main Authors: Bonaldo, Federico, Mattivi, Fulvio, Catorci, Daniele, Arapitsas, Panagiotis, Guella, Graziano
Format: Article
Language:English
Subjects:
Anthocyanins
Antioxidants
Aromatic compounds
Catechin
Deuteration
Epicatechin
Equilibrium
Flavanols
Flavones
Flavonoids
Flavonols
H/D isotopic exchange
Hydrogen-deuterium exchange
kinetics
Molecular modelling
NMR spectroscopy
Quercetin
reaction mechanism
Reaction mechanisms
Solvent effect
Solvents
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Summary:Several classes of flavonoids, such as anthocyanins, flavonols, flavanols, and flavones, undergo a slow H/D exchange on aromatic ring A, leading to full deuteration at positions C(6) and C(8). Within the flavanol class, H-C(6) and H-C(8) of catechin and epicatechin are slowly exchanged in D2O to the corresponding deuterated analogues. Even quercetin, a relevant flavonol representative, shows the same behaviour in a D2O/DMSOd6 1:1 solution. Detailed kinetic measurements of these H/D exchange processes are here reported by exploiting the time-dependent changes of their peak areas in the 1H-NMR spectra taken at different temperatures. A unifying reaction mechanism is also proposed based on our detailed kinetic observations, even taking into account pH and solvent effects. Molecular modelling and QM calculations were also carried out to shed more light on several molecular details of the proposed mechanism.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules26123544