Concentrations of selected polyphenols in white commercial wines

Using an HPLC method with diode array detection, we have measured the conce ntrations of flavan 3-ols (catechin and epicatechin), trihydroxystilbenes ( the cis and trans isomers of polydatin and resveratrol), flavonols (quercet in and rutin), and the hydroxy acid p-coumaric in 644 white wines from the major wine-producing regions. Quercetin and rutin were detectable in very f ew of these wines, and the latter could not be unequivocally distinguished from isoquercitrin, which was not specifically measured in this study. One or more of the hydroxystilbenes were measurable in most, but the cis isomer s of polydatin and resveratrol were not frequently detectable. Among Chardo nnay wines, those from Australia had the highest concentrations of both fla van 3-ols, while those from California were highest in p-coumaric acid and trans-resveratrol. For Sauvignon blanc wines, those of South Africa had the highest content of both flavan 3-ols, For Riesling wines, those from Franc e (Alsace) were highest in (+)-catechin and trans-resveratrol, German wines in (-)-epicatechin, and Canadian wines in trans-polydatin. French wines fr om Pinot (blanc and gris) were higher in all constituents than North Americ an, while Italian wines from this cultivar were the lowest. There were no s ignificant differences in polyphenol concentrations between Gewurztraminer wines from France and North America. Low concentrations of polyphenols were found in miscellaneous white wines from Central Europe and Italy, When ana lyzed by cultivar rather than by region, highest flavan 3-ol concentrations were observed in wines from French hybrid grapes (Vidal blanc and Seyval b lanc) and lowest in Gewurztraminer, whereas the former had lowest concentra tions of p-coumaric acid and trihydroxystilbenes. In all instances, the con centrations of the polyphenols measured in white wines were 5% to 25% those of red wines (with quercetin and cis-trihydroxystilbenes being undetectabl e in most) and do not explain why white wines may have the same potency as red wines in certain biological functions. Climatic factors that appear to modulate polyphenol concentrations in red wines such as stress, fungal pres sure and sunlight do not seem to be important for white wines, The intrinsi c properties of the individual cultivars or clones together with regional d ifferences in enological techniques may be the most important factors.