Anthocyanin reaction

Lu, Y. and Foo, L.Y.,Unusual anthocyanin reaction with acetone leading to pyranoan-thocyanin formation. Tetrahedron Lett., 42, 1371, 2001. 

Anthocyanin reaction products Caffeoyltartaric acid-malvidin 3-0-glc adducts (e.g., 5 1, Figure 5.4)... 

FIGURE 5.S Anthocyanin reactions with caffeoyltartaric acid o-quinone coupled oxidation of cyanidin 3-glucoside (A) and nucleophilic addition of anthocyanins (B). Anthocyanin-caffeoyltartaric acid adducts are represented as one of the possible isomers, namely 2-(8-anthocyanin) caffeoyltartaric acid (5 1). 

Finally, reactions of flavonoid and nonflavonoid precursors are affected by other parameters like pH, temperature, presence of metal catalysts, etc. In particular, pH values determine the relative nucleophilic and electrophilic characters of both anthocyanins and flavanols. Studies performed in model solutions showed that acetaldehyde-mediated condensation is faster at pH 2.2 than at pH 4 and limited by the rate of aldehyde protonation. The formation of flavanol-anthocyanin adducts was also limited by the rate of proanthocyanidin cleavage, which was shown to take place at pH 3.2, but not at pH 3.8. Nucleophilic addition of anthocyanins was faster at pH 3.4 than at pH 1.7, but still took place at pH values much lower than those encountered in wine, as evidenced by the formation of anthocyanin-caffeoyltartaric acid adducts, methylmethine anthocyanin-flavanol adducts,and flavanol-anthocyanin adducts. The formation of pyranoanthocyanins requiring the flavylium cation was faster under more acidic conditions, as expected, but took place in the whole wine pH range. Thus, the availability of either the flavylium or the hemiketal form does not seem to limit any of the anthocyanin reactions. 

Finally, the relative amounts of anthocyanin-flavanol pigments and anthocyanin-anthocyanin pigments obviously depend on the anthocyanin to flavanol ratio. However, the kinetics of anthocyanin polymerization and flavanol-anthocyanin reactions as well as the quantities of the resulting pigments in wine remain to be established. Consequently, the importance of these processes with respect to other anthocyanin reactions (hydration and subsequent degradation, cycloadditon with yeast metabolites) and the impact of resulting polymeric anthocyanins on wine quality are speculative. 

Figure 1. Tannin-Anthocyanin reactions mediated by acetaldehyde (Cheynier, 2001).

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