Flavonols in wines

Volikakis, G.J. and Efstathiou, C.E. (2005) Fast screening of total flavonols in wines, tea-infusions and tomato juice by flow injection/adsorptive stripping voltammetry. Anal Chim Acta, 551 (1-2), 124-131. 

Hertog, M.G.L. (1998). Flavonols in wine and tea and prevention of coronary heart disease. In Polyphenols 96 (eds J. Vercauteren, C. Cheze 1. Triaud), pp. 117-131. INRA Editions, Paris. 

CZE is particularly useful for separating anthocyanin dimers or polymeric anthocyanins. Calvo et al. (2004)" separated 13 anthocyanins by CZE including acylated and non-acylated anthocyanins, pyranoanthocyanins, and flavonol derivatives in wine. Saenz-Lopez et al. (2004)" applied CZE to analyze wine aging (1 to 14 yr) as related to monomeric anthocyanins, anthocyanin derivatives, tannins, and fla-vonols. Bicard et al. (1999)" reported the improved detection sensitivity of anthocyanin chemical degradation analysis by CZE. 

Makris DP, Kallithtaka S and Kefalas P. 2006. Flavonols in grapes, grape products and wine burden, profile and influential parameters. J Food Compos Anal 19 396-404. 

For the red wines (82-84), which were injected directly into the HPLC without sample preparation, a ternary-gradient system using aqueous acetic acid (1% and 5% or 6%), and acidified acetonitrile (acetonitrile-acetic acid-water, 30 5 6) was used for cinnamic acid derivatives, catechins, flavonols, flavonol glycosides, and proanthocyanidins. Due to the large number of peaks, the gradient was extended to 150 min for the resolution of many peaks of important phenolics. This direct injection method was able to separate phenolic acids and esters, catechins, proanthocyanidins, flavonols, flavonol glycosides, and other compounds (such as tyrosol, and rrans-resveratrol) in wine in a single analysis. However, use of acetic acid did not permit the detector (PDA) to be used to record the UV spectra of phenolics below 240 nm (84). 

The concentration in wine is ca. 2(MK)mg/K (75MI1,98JAFC368), and these flavonols are found as glycosides, as, for example, 3-O-rhamno-sylquercetin with R3=rhamnose. 

Similar assay of the detection systems is performed by Stecher et al., who analyzed flavonols and stilbenes in wine and biological products and found that ESI-MS detection gave two, three, and nine times lower limit of detection (LOD) for myricetin, quercetin, and kaempferol. 

Figures 2.17 and 2.18 show the chromatograms relative to analysis of HCTA and flavonols in Raboso and Brunello di Montalcino wines, respectively.

Currently, LC/MS and multiple mass spectrometry (MS/MS) have been used to study the grape polyphenols (anthocyanins, flavonols, tannins and proanthocyanidins, hydroxycinnamic, and hydroxycinnam-oyltartaric acids), which allow to structurally characterize and understand the mechanisms involved in stabilizing the color in wines (Flamini, 2003). 

Several colourant materials for example those in fruit, tea and in wine which have been used historically world-wide and bear no E numbers have more recently been judged to have useful health properties probably through their role as antioxidants (ref. 119). Thus in this class can be instanced the flavonol, epicatechin, the flavanoid quercitin, the stilbene referred to earlier, resveratrol. and theaflavin, the colourant of black tea (ref. 120), (the absolute configuration of this is not known). 

It is a fact that phenolic compounds, namely flavonoids, play a crucial role in wines as they are responsible for the color of red and white wines and contribute to their mouth characteristics (astringency and bitterness). In Vitis vinifera grapes and wines, this group of compounds is structurally diversified and comprises different classes of compounds, such as anthocyanins, flavan-3-ols (catechins and condensed tannins), flavonols, flavones, and dihydroflavonols. 

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