Phenolic compounds and flavonoids as part of bioactive substances in grape pomace extracts from six cultivars of Vitis vinifera L. grown in the Tajna locality (Slovakia)

Grape pomace (GP) is considered a good source of antioxidant active phenolic compounds, including phenolic acids and flavonoids. GP extracts from six Vitis vinifera cultivars were used to determine total polyphenol content, selected flavonoids (myricetin, quercetin, kaempferol, and rutin), phenolic acids (gallic, sinapic, cinnamic, and p -coumaric acids), and antioxidant activity (DPPH, FRAP). The total polyphenol content was from 15.1 (cv. Merlot) to 36.4 (cv. Cabernet Franc) mg GAE/g dry weight (DW), the myricetin content was max. 28.5 (cv. Merlot), quercetin 109 (Cabernet Franc), kaempferol 26.4 (cv. Cabernet Franc) and rutin 66.6 (cv. Cabernet Sauvignon) mg/kg DW in GP extracts. The content of gallic acid was 7.61–70.1, sinapic acid BDL–47.1, cinnamic acid BDL–6.34, and p -coumaric BDL–7.60 mg/kg DW (BDL – below detection limit). The highest antioxidant activity (DPPH method) was determined in GP extract from cv. Dunaj and Cabernet Franc (24.4 µmol TE/g DW), resp. in GP extract cv. Cabernet Franc (91.5 µmol TE/g DW – FRAP method). The aim of the study was to quantify selected biologically active substances present in Vitis vinifera pomace.