Quercetin and p-coumaric acid concentrations in commercial wines

Using analytical methods based upon high performance liquid chromatography, the quercetin and p-coumaric acid concentrations were analyzed in 872 and 547 commercial red wines, respectively, from 14 of the world's leading wine-producing regions or countries. Quercetin concentrations were clearly highest in wines from warmer climates notable for high sunshine including Australia, California, South Africa, South America, Midi, and Provence, an exception being the Rhone Valley region of France. Among wines from individual cultivars, those of Pinot noir were consistently the lowest, although the Oregon wines from this cultivar matched the quercetin concentrations of Cabernet Sauvignon and Merlot-based wines from neighboring Washington State. The distribution of p-coumaric acid in red wines seemed to be more random than that of quercetin. Highest values were observed in Cabernet Sauvignon and Merlot wines from Bordeaux, Australia, California, Washington State, and South Africa. Climate and sunlight appeared to be less consistent determinants of concentration than was the case with quercetin, and genetically determined metabolic set-points may be more relevant for this key phenolic acid that acts as a precursor of trihydroxystilbenes as well as of flavonoids and flavan 3-ols.