Anthocyanins reaction between

Fulcrand, H. et al., A new class of wine pigments generated by reaction between pyruvic acid and grape anthocyanins. Phytochemistry, 47, 1401, 1998. 

Fig. 2.102. Structures of all the compounds found in fraction A (a) anthocyanins (b) A-type vitisins (c) pyranoanthocyanins originated by reaction between anthocyanins and vynilphenol, vynilcatechol or vynilguaiacol (d) pyranoanthocyanins originated by reaction between anthocyanins and vynil(epi)catechin. Reprinted with permission from C. Alcalde-Eon et al. [236],...

Es-Safi, N.E., Cheynier, V., and Moutounet, M., Study of the reactions between (+)-catechin and furfural derivatives in the presence or absence of anthocyanins and their implication in food color change. J. Agric. Food Chem. 48, 5946, 2000. 

Benabdeljalil, C. et al.. Evidence of new pigments resulting from reaction between anthocyanins and yeast metabolites. Set Aliment, 20, 203, 2000. 

As a first approximation, this experiment represents the evolution of the coloring matter in red wines during aging. It confirms the large role of tannins in the color of old wines and thus shows that tannins play an important part in the color of young wines. Taken as another point, the possibility of a reaction between the anthocyanins and tannins already postulated (50) is accurately described. 

Mechanism of reaction. The mechanism of the reaction between anthocyanins and 4-vinylphenols was first proposed by Fulcrand et al. (1996). Hydroxyphenyl-pyranoanthocyanins result from the cycloaddition of the ethylenic bond of the 4-vinylphenol molecule at positions C-4 and C-5 of the anthocyanin followed by an oxidation process, resulting in a pyrane ring (Fulcrand et al. 1996) for which this type of compound receives the name of pyranoanthocyanins (Fig. 9A.3f). The vinylphenol addition at C-4 protects the anthocyanin of being hydrated. 

Mechanism of reaction. The adduct of malvidin-3-glucoside with pyruvic acid, also known as vitisin A(Fig. 9A.3h), was firstly detected in fortified red wines (Bakker et al. 1997) and in a grape marc (Fulcrand et al. 1998) and further isolated and characterized by NMR (Bakker et al. 1997 Fulcrand et al. 1998). According to Fulcrand et al. (1998), the reaction between pyruvic acid and grape anthocyanins occurs through a series of steps similar to those previously described for the hydroxyphenyl-pyranoanthocyanins (Sect. 9A.2.4.1 Fig. 9A.3f). Later studies performed by NMR (Mateus et al. 2001b) and mass spectrometry (Asenstorfer et al. 2001 Hayasaka and Asenstorfer 2002) have confirmed the structure proposed by Fulcrand et al. (1998). This mechanism is extended to the condensation reaction between anthocyanins and other enolizable precursors found in wine (Benabdeljalil et al. 2000). 

Factors affecting the reaction. The extent of the reactions between anthocyanins and pyruvic acid in model solutions follows a first order kinetic with respect to the anthocyanin disappearance. This reaction is affected by several factors, such as anthocyanin composition, pH, pyruvic acid concentration, temperature and acetaldehyde concentration. The maximum formation took place at pH 2.7-3.0 due to requirement of the anthocyanin fiavylium form, at high pyruvic acid concentration, at low storage temperature (10-15 °C) and in the absence of acetaldehyde (Romero and Bakker 1999a,b, 2000a,b). 

Oliveira, J., De Freitas, V., Silva, A.M.S., Mateus N. (2007). Reaction between hydroxycin-namic acids and anthocyanin-pyruvic adducts yielding new portisins. J. Agric. Food Chem. 55, 6349-6359. 

Other pigment families have been shown to occur in red wine, like anthocyanin oligomers (Salas et al. 2005 Vidal et al. 2004a), caftaric acid-anthocyanin adducts (Sarni-Manchado et al. 1997) or catechin-pyrylium derived pigments (i.e., oaklins) resulting from the reaction between catechin and wood aldehydes, like coniferalde-hyde or sinapaldehyde (de Ereitas et al. 2004 Sousa et al. 2005). These... 

Both flavanol-anthocyanin pigments and colorless A(-0-)F have been detected in wines 11). Mass signals do not allow to distinguish between F-A+ and A+-F derivatives. However, dimeric anthocyanins consisting of one unit under flavylium cation and the other one under hydrated hemiketal form (A+-AOH) were characterized by mass spectrometry in wine like solutions (72). The existence of such structures arising from direct reactions between anthocyanin molecules confirms that they react both as nucleophiles and as electrophiles in wine. 

Similarly, direct reactions between anthocyanins and a flavanol dimer (namely epicatechin-epicatechin 3-gallate) were investigated in model solutions at pH 2 and pH 3.8 (31). Compounds with mass values corresponding to epicatechin-anthocyanin adducts and to anthocyanin-epicatechin-epicatechin 3-gallate, were detected at pH 2 and pH 3.8, respectively. Given the structure of the flavanol precursor, the former can be interpreted as F-A+ arising from cleavage of the flavanol dimer followed by addition of the anthocyanin AOH form onto the epicatechin carbocation whereas the latter is presumably an A+-F species formed by nucleophilic addition of the flavanol dimer onto the flavylium cation. Anthocyanin dimers (A+-AOH) were detected in model solutions at pH... 

Thus, it seems that the major changes induced by micro-oxygenation are due to acetaldehyde reactions (figure 6). In a first stage, acetaldehyde-induced reaction between anthocyanins and flavanols leads to purple ethyl-linked pigments. These intermediate pigments have been shown to be rather unstable... 

---