red wines, they are usually the most abundant class of
phenolics in free-run juice and consequently in white wines
(Adams 2006), where they contribute for white wine colour
browning under oxydation, in association with non phenolic
molecules (Blouin and Cruège 2003; Kennedy et al. 2006).
In the sub-epidermal tissue of DeChaumac grape two major
hydroxycinnamic acid esters, tartrate esters of p-coumaric
and caffeic acids are found; their concentrations in fresh
grape skins being 0.222 and 0.757 µmol/g, respectively
(Moskowitz and Hrazdina 1981).
A nonflavonoid compound class that, although present
in trace quantities in wine, has been drawing attention are
the stillbenes, and more specifically resveratrol (Fig. 8).
This molecule attracted little interest when it was discovered
in 1940, but, after it was postulated to be responsible
for some of the cardioprotective effects of wine in 1992, the
number of papers testing its effects both in vitro and in vivo
has been increasing exponentially, and it is now linked to
many of the beneficial effects of wine (reviewed by Baur
and Sinclair 2006). This compound is found in the skin of
the grape berry in response to attack from fungi, mainly
Botrytis cinerea (Ebel 1986), and can be present in its free
form or as a glucoside, piceid. Its concentration in red wine
can vary from 0.1 to 12 mg/L (Goldberg et al. 1994) and,
despite being much lower than the concentration of other
phenolics present in wine, it is the only known source of
dietary resveratrol, thus justifying the attention it has been
receiving recently.