Biology Reference
In-Depth Information
their C-1 position, with nucleophilic species in wine. Of course, this type
of chemical reaction is just one among several other processes leading to
the transformation of native
C
-glycosidic ellagitannins extracted from
oak-made casks by wine solutions.
Table 9.1 Levels of vescalagin, castalagin, ethylvescalagin and acutissimins in a sample
of red wine aged in oak barrels.
Compound
Concn (mg/L)
vescalagin (
1
)
2.20 ± 0.15
castalagin (
2
)
8.10 ± 0.31
ethylvescalagin (
31
)
0.85 ± 0.05
acutissimin A (
14
)
0.40 ± 0.03
acutissimin B (
15
)
0.28 ± 0.02
epiacutissimin A (
29
)
0.30 ± 0.02
epiacutissimin B (
30
)
0.35 ± 0.02
Moreover, it is important to keep in mind that wine is a complex
multi-component reaction system, which slowly but continuously
evolves under mildly acidic and oxidative conditions. As far as the
acutissimins are concerned, they are further transformed in wine, as we
shall illustrate below (Section 9.3.4), but they will continue to form as
long as grape flavan-3-ols and oak vescalagin (
1
) are present in the wine
solution. Furthermore, red wine, more than white wine, is particularly
rich in various components derived from grape (skin and seeds) and its
fermented juice, and contains a broad panel of nucleophilic species,
which may compete in the trapping of the benzylic cation intermediate
27
derived from
1
during its condensation reactions at C-1. Examples
of such nucleophiles are numerous other flavonoids (
e.g.
, from
procyanidins to proanthocyanidins, and anthocyanins) and, more
generally, a large library of all kinds of phenols, alcohols, amines,
carboxylic acids, enolizable carbonyl compounds, and thiols (Cabanis
et al.
, 1998), including macromolecules such as proteins and
polysaccharides that feature some of these functional groups. The
quantitative search by any given analytical method of each of the
compounds possibly resulting from a condensation reaction between one
of these nucleophiles and vescalagin at any given time during the aging
process of a wine can certainly fuel research for many years to come.
