Anthocyanins reactivity

The precursors of these reactions are, on one hand, proanthocyanidins and, on the other hand, any kind of flavonoid that can act as a nucleophile. The latter include flavonols, dihydroflavonols, flavanol monomers, proanthocyanidins, and anthocyanins under their hemiketal form (for anthocyanin reactivity, see Chapter 9A). 

The third group of wine pigments corresponds to pyranoanthocyanins (fig. 3c) formed, as described in die anthocyanin reactivity section, by reaction of genuine anthocyanins with yeast metabolites released during fermentation (d)... 

Cyanidin 3-O-b-D-glucoside (C3G) of a typical anthocyanin pigment could lower the serum thiobarbituric acid-reactive substance concentration and increase the oxidation resistance of the serum to lipid peroxidation in rats [52]. In vitro enzymatic and non-enzymatic polyunsaturated fatty acid per oxidation was significantly inhibited in a dose-dependent manner by anthocyanin [53], a deep-red color pigment from carrot cell cultures. 

It is critical to recognize the high reactivity and low stability of anthocyanins in the selection of methods of extraction and quantitation in the analysis of anthocyanins. An analysis of processed samples containing anthocyanins for polymeric color as well as monomeric anthocyanins is recommended in nutrition studies until we better understand any health effects (positive or negative) of the compounds that are part of the mix measured as polymeric color. ... 

Grapes contain several hydroxycinnamic acids, p-coumaric, caffeic, ferulic and sinapic acids, which exist as free acids and esterified with tartaric acid. Saccha-romyces species can take up free acids to produce the corresponding vinyl phenol catalysed by hydroxycinnamate decarboxylase (phenylacrylic acid decarboxylase Padlp) (Fig 8D.11) (Chatonnet et al. 1992b Chatonnet et al. 1993 Edlin et al. 1995). Vinyl phenols are unstable and highly reactive. Dekkera bruxellensis is one of few wine microorganisms that can further reduce vinyl phenols to highly stable ethyl phenols in wine. Vinyl phenols can also react with anthocyanins to form vinyl derivatives, a reaction that is favoured by fermentation yeast having hydroxycinnamate decarboxylase activity (Morata et al. 2006). 

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