452 M. Monagas and B. Bartolom ́e
was similar to that of their precursor in grapes. The concentration of malvidin-3-
glucoside-based flavanyl-pyranoanthocyanins was higher than those of malvidin-
3-(6-p-coumaroyl)-based pigments. Pyranoanthocyanin-procyanidin adducts were
more abundant than the corresponding monomeric ones and among these latter
forms, pyranoanthocyanin-(–)-epicatechin were higher that the corresponding (+)-
catechin derivatives.
Factors affecting the reaction.To date there has been only one study in relation to
the evolution of these pigments during wine aging. According to He et al. (2006a),
the concentration of flavanyl-pyranoanthocyanin could be affected during wine
aging. An increase in the concentration of (+)-catechin and (–)-epicatechin deriva-
tives of pyranomalvidin-3-glucoside was observed from 3 to 6 years of aging,
probably due to the increase of the vinyl(epi)catechin precursors from ethyl-linked
(epi)catechin oligomers or to the hydrolysis of the corresponding acylated pyra-
noanthocyanins.
9A.2.4.3 Condensation Reaction Between Anthocyanins and Enolizable
Aldehydes and Ketones: Carboxy-Pyranoanthocyanins and Related
CompoundsPrecursors. Precursors for this reaction arecompounds exhibiting keto-enol tau-
tomerism. These compounds are usually secondary metabolites derived from the
glycolysis cycle of yeast metabolism during fermentation. Pyruvic acid is one of the
main precursor compounds involved in this type of reaction. During yeast fermenta-
tion it is decarboxylated to acetaldehyde and then reduced to ethanol. Acetone, ace-
toin (3-hydroxybutan-2-one), oxalaceticacid, acetoacetic acid and diacetyl, among
others, are also secondary metabolites likely to participate in this kind of condensa-
tion reaction with anthocyanins.
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 iso-
lated and characterized by NMR (Bakker et al. 1997; Fulcrand et al. 1998). Accord-
ing to Fulcrand et al. (1998), the reaction between pyruvic acid and grape antho-
cyanins 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).
Evidence in wine. The carboxy-pyranoanthocyanins have been extensively stud-
ied in wines. The derivatives of malvidin-3-glucoside and of itsp-coumaroyl and
acetyl esters, were first identified both in red wines (Revilla et al. 1999; Vivar-
Quintana et al. 1999; Asenstorfer et al. 2001; Hayasaka and Asenstorfer 2002;
Atanasova et al. 2002a; Heier et al. 2002; Alcalde-Eon et al. 2004, 2006; Monagas
et al. 2003; Morata et al. 2003a; Pozo-Bay ́on et al. 2004; Boido et al. 2006) and in
Port wines (Bakker et al. 1997; Romero and Bakker 2000b; Mateus et al. 2003a).