Macrowine 2021

A mechanistic investigation of H/D scrambling processes in flavonoids

Abstract

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 scrambling 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.

DOI:

Publication date: September 16, 2021

Issue: Macrowine 2021

Type: Article

Authors

Graziano Guella

Biorganic Chemistry Lab/Dept. of Physics/University of Trento,Federico Bonaldo1, Fulvio Mattivi2, Daniele Catorci*, &, Panagiotis Arapitsas3, Graziano Guella1, * 1  Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, Trento, Italy; 2 Department of Cellular, Computational and Integrative Biology – CIBIO and C3A, University of Trento, Trento, Italy; 3 Department of Food Quality and Nutrition, Research and Innovation Centre, Fondazione Edmund Mach (FEM), San Michele all’Adige, Italy; * D. Catorci passed away on June 27th, 2020

Contact the author

Keywords

flavonoids; chemistry of polyphenols; h/d isotopic scrambling; reaction mechanism

Citation

Related articles…

Phenolic, antioxidant, and sensory heterogeneity of oenological tannins: what are their possible winemaking applications?

AIM: The aim of this work was to characterize 18 oenological tannins by the polyphenolic, antioxidant, and sensory point of view.

Read More

Protein extracts of the Andean pseudocereals quinoa and kiwicha as alternatives for the fining of wine phenolics.

INTRODUCTION: Lately, there has been an increasing interest in using plant-derived proteins for wine phenolic fining.

Read More

First application of an original methodology created to overcome conflicts between stakeholders in an important wine-growing territory: methodology, results, and perspectives in the application of sustainability EME4.1C

Considering the previous research and activities, also, on Sustainability EME4.1C which, as widely known, considers in a harmonious chain all the factors material, immaterial, moral and spiritual related to all aspects environmental, economic, social, existential, relational, ethical, technical and “MetaEthic” indexed 4.1C

Read More

Crown procyanidin quantification in red wines, rosé wines and Port wines

Condensed grape tannins play a major role in the organoleptic properties and quality of red wine. Recently, a new sub-family of macrocyclic condensed tannins has been identified in red wine and named “crown tannins”. Indeed, the first compound of the family identified and characterised by NMR was the crown procyanidin tetramer which is composed of a macrocyclic structure composed of four (-)-epicatechins link together by B-type interflavanoid linkage in the following an alternative sequences of C4-C8 and C4-C6 linkage. The 3D structure of this unusual crown procyanidin family reveals a central cavity in the molecule [1].

Read More

Unveiling a hidden link: does time hold the key to altered spectral signatures of grapevines under drought?

Remote sensing technology captures spectral data beyond the visible range, making it useful for monitoring plant stress. Vis-NIR (Visible-Near Infrared) spectroscopy (400-1000 nm) is commonly used to indirectly assess plant status during drought. One example is the widespread use of normalized difference vegetation index (NDVI) that is strongly linked to green biomass. However, a knowledge gap exists regarding the applicability of this method to all the drought conditions and if it is a direct correlation to the water status of the plant.

Read More