trans-Caftaric acid was the predominant hydroxycinnamic acid for both Merlot and Syrah, amounting to 35 mg/L in both fresh wines. trans-Coutaric acid concentration in fresh Syrah wine was threefold higher (16.8 mg/L) than the respective concentration in Merlot, while caffeic and coumaric acid were found in traces in both varieties. These observations are in agreement with Makris et al. (2006), Puértolas et al. (2011), and support their suggestion that trans-caftaric and trans-coutaric acid could be ‘marker compounds’for the differentiation of young wines in function of the cultivar. Also, Rodríguez Montealegre et al. (2006) found a similar content of trans-caftaric acid in Merlot and Syrah grape skins, but a twofold higher content of trans-coutaric acid in Syrah.