Preliminary study of flavonols in port wine grape varieties

Seven varietal port wine grapes (Tinta Roriz, Tinta Barroca, Tinta Amarela, Tinta Cão, Touriga Francesa, Touriga Nacional and Rufete) were analysed in order to determine differences in flavonol compositions. For this purpose, a SPE-HPLC method was applied. Although no qualitative variations were found, there are quantitative differences in the individual concentrations of the phenolic compounds. In Tinta Cão and Rufete varieties, (−)-epicatechin was the major compound. All samples showed significant amounts of kaempferol 3-glucoside and isorhamnetin 3-glucoside, with the exception of Rufete variety, where these compounds were present in traces.