Anthocyanins, flavonols and hydroxycinnamates: an attempt to use them to discriminate Vitis vinifera L. cv 'Barbera' clones

Anthocyanin and flavonol profiles of Vitis vinifera berry skin have been diffusely studied in past years to identify the effects exerted by climate, environment and cultural practices on their biosynthesis. They have also been used for chemotaxonomic purposes with the aim of classifying grape varieties. Hydroxycinnamates and phenolic acids are the most important group of non-flavonoid phenols in grapes and wines. In the present work six 'Barbera' clones were grown in the same site to evaluate the influence of two seasons on the accumulation of flavonoids and hydroxycinnamates at maturity. Berry skins were extracted in an ethanolic buffer and flavonoids and hydroxycinnamates were separated by HPLC. Two principal component analysis (PCA) models were built to identify phenolic parameters exploitable to classify clones. The PCA scores were taken further to perform discriminant analysis to evaluate the degree of classification possible. A significant seasonal variability was observed for most phenolic features, whereas some parameters such as total anthocyanin expressed on a per berry basis, the sum of tri-hydroxylated anthocyanin percentages, the percentages of kaempferol glucuronide and the total hydroxycinnamate content were stable over the seasons. The percentage of individual anthocyanin alone, not associated with maturity data, was not effective in classifying clones; in association with maturity data it allowed to discriminate clones, similarly to what it was previously assessed for classifying varieties. The results indicated that LDA models developed on the PCA scores including maturity data correctly classified 75% of clones.