12/17/2011

Wines of Uruguay

TANNAT & HEALTH

During the past decade, many epidemiological studies have shown that the Mediterranean diet appears to have beneficial effects on cardiovascular diseases, which have has been labelled as the “French Paradox” [St. Legere et al, 1979]. The regular and moderate consumption of wine, especially red wine, appears to be one of the main reasons for these potential health effects.

Flavan-3-ols or flavonoids, such as catechin, epicatechin and procyanidins, contribute to the major antioxidant activity of red wines in the prevention of LDL cholesterol oxidation [Teissedre et al, 1996]. The amount of flavonoids in red wine depends on the grape variety, cultivation area, sun exposure, wine-making technique and wine age [Auger et al, 2004; Burns et al, 2000; Dell´agli et al, 2004]. Stilbene derivatives present in red wines, such as resveratrol, are also postulated as the compounds responsible for the French Paradox. The measurement of resveratrol levels in Tannat wines found an average of 2.7 mg/l, a higher value than reported for Pinot Noir, Merlot and Cabernet wines [Gu et al, 1999].
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Tannat wines were shown to have one of the highest levels of phenolic compounds reported for vinifera grape varieties [Boido et al, 2011]. The anthocyanin profile of grapes, young wines and wine aging have been characterized and compared with other grape varieties [Alcalde-Eon et al, 2006; Boido et al, 2006]. More recently, the profiles for different polyphenol families and OPC present in Tannat grapes (skins and seeds) and wines were determined all along the maturation process of the grapes in Uruguayan vineyards [Boido et al, 2011].

Tannat antioxidant activity
Red wine consumption has been tied to the prevention of pathologies associated with oxidative stress; antioxidant phenolic compounds have been suggested as being responsible for this effect. Although a correlation between the antioxidant properties of red wine and its content of phenolic compounds such as flavanols, anthocyanins and tannic acid, has been described, the antioxidant properties of red wine have been linked with total polyphenol concentration rather than individual polyphenols [Burns et al, 2001].
In this context, it was studied the factors influencing the antioxidant capacity and phenolic composition of red wines under different viticulture practices, vinification and maturation processes for Tannat [Carrau et al, 2011]. Some authors found in the Tannat wines studied, that antioxidant capacity increased with aging, although most of the phenolic families remained constant, suggesting the relevance of qualitative changes in these compounds for antioxidant capacity [Echeverry et al, 2005]. In another study led by Echeverry et al. [2004] assessed the cytoprotective capacity of Tannat wine and its phenolic fractions against an oxidative stress stimulus in the pheochromocytoma cell line PC12. The results pointed to natural polyphenols as potential neuroprotective compounds and showed the specific phenolic fraction that is involved in wine cytoprotective properties, perhaps acting synergistically.
Guigluicci et al. [2001] reported biochemical changes on the wine flavonoids during aging, modifying their antioxidant properties. The researchers paid particular attention to the polyphenols of Tannat wine using human low-density lipoprotein (LDL) as a clinical model and spectroscopic analysis to follow oxidation products. The research reported that younger Tannat wines had a more active inhibition of the LDL oxidation by peroxinitrite and lipooxigenase and, as was expected, found that shorter macerations time during vinification and barrel aging could also decrease this capacity.
On the other hand, Tannat wines with total polyphenol content similar to those of Californian Merlot and Cabernet Sauvignon demonstrated a double inhibition effect in the oxidation of LDL (Guigluicci et al, unpublished results). The dilution factor for these experiments in a standard red wine is about 1/1000 [Frankel et al, 1993], while for the Tannat wines dilutions up to 1/3000 were necessary to discriminate the different treatments. Interestingly, they also found that a bottle could lose 30% of its antioxidant capacity in 6 hours after it was open.
Based on these results, Bracesco et al. [2007] analysed the possible genome protection provided by Tannat wine in yeast cell populations exposed to H2O2. Haploid and diploid strains of Saccharomyces cerevisiae were used as a eukaryotic model. Cell samples were exposed to H2O2 in a nutrient medium. Chromosomal DNA was analysed after isolation and separation by pulsed field electrophoresis. Double-strand breaks were determined by laser densitometry and the application of Poisson distribution. Both haploid and diploid cells showed H2O2 dose-dependent DNA fractionation, as well as an increase of lethal and mutation events. Upon combining the Tannat wine and H2O2, a significant decrease of double strand breaks was observed, in association with an increase in surviving fractions. Moreover, no mutagenic effect was observed after wine exposure. Part of the observations regarding this protective wine effect was simulated by exposure to high concentrations of α-tocopherol. These results indicate that a grape derivative could act as a genome protector, increasing the probability of cell survival. Among other things, the involved molecular targets could be components of transduction redox cascades as well as DNA repair enzymes.


Tannat: Signature red of Uruguay, one example of the many interesting wines now fighting for shelf space from all over the world.
The ABCs of Wine Updated Glossary by Dorothy J. Gaiter and John Brecher
The Wall Street Journal, Sunday May 16, 2009.