Identification of polyphenolic compounds in red and white grape varieties grown in R. Macedonia and changes of their content during ripening

The composition of polyphenols in the skin, seed and pulp extracts of the grapes of Vranec and Smederevka varieties, and Merlot and Chardonnay as well, was analyzed by liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS) and MS/MS techniques. Thirty-one phenolic compounds, including anthocyanins, flavonols and flavan-3-ols, as well as phenolic acids derivatives, have been identified in the extracts prepared from the grapes at physiological maturity, by mass spectrometry applying electrospray ionization operated in alternating ion mode and by performing tandem MS experiments in the ion trap mass analyzer. Grapes were analyzed at three different phases: (i) veraison, (ii) physiological ripeness and (iii) late harvest, in order to follow the evolution of polyphenolic content during berry development, applying spectrophotometric methods. Vranec had a higher polyphenolic content compared to Merlot due to the higher levels of total phenolics and flavonoids in the skins and seeds as well as a higher content of flavan-3-ols and anthocyanins in the skins, allowing discriminating the varieties. HPLC-DAD-MS analysis presented significantly higher relative amounts of anthocyanin monoglucosides and p-coumaroylglucosides in Vranec grapes. Smederevka seeds had a higher amount of flavan-3-ols than Chardonnay, while a higher content of total phenolics and flavonoids was found in the skins of the Chardonnay variety. Anthocyanin content in both red varieties increased during the berry ripening, while flavan-3-ols in seeds were mainly accumulated in the veraison phase followed by decrease of the content with ripening.

► Polyphenols in grapes Vranec, Merlot, Smederevka and Chardonnay were analyzed.
► The changes were examined at veraison, physiological ripeness and late harvest.
► Vranec and Chardonnay showed higher phenolic content than Merlot and Smederevka.
► The anthocyanins increased and the flavan-3-ols decreased during the ripening.