Free radical scavenging of grape pomace extracts from Cabernet sauvingnon (Vitis vinifera)

Pressed grape pomace obtained from the wine production of Cabernet sauvignon (Vitis vinifera) vintage was dried until 9.8% moisture content, ground and submitted to extraction of soluble components from different extraction techniques. Low pressure extractions were performed with ethanol maceration followed by fractionation with n-hexane, dichloromethane, butanol and ethyl acetate. These solvents were furthermore applied for soxhlet extraction. Supercritical fluid extraction (SFE) was also performed to obtain grape pomace extracts by using pure CO2 and CO2 with ethanol as co-solvent in concentrations of 10, 15 and 20% w/w. The operating condition used in high pressure extractions was 150 bar and 40 °C. The antioxidant activity of the grape pomace extracts was determined considering the free radical scavenging assay using 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and was correlated with the total phenol content determined according to the Folin–Ciocalteu method. The results obtained in DPPH tests indicate the highest antioxidant activity of 96.6 ± 0.3% AA, with an IC50 value of 13 ± 1, for the extracts obtained with ethyl acetate in solid–liquid extraction. The highest yield values were achieved in soxhlet extraction with ethanol (13.2% w/w) and with butanol (12.2% w/w), and also by SFE with 15% ethanol (9.2% w/w). The lipophilic composition of grape pomace extracts was evaluated by gas chromatography–mass spectrometry with the identification of components like linoleic acid and ethyl linoleate, with important therapeutic activities.