Pressurized liquid extraction of bioactive compounds from grape marc

Extracts rich in monomeric anthocyanins (MAC) and total phenolic compounds (TPC) were obtained from grape marc by Pressurized Liquid Extraction (PLE). PLE was performed using ethanol and water mixtures (acidified or not) (50% w/w), pure ethanol and acidified water at temperatures from 40 to 100 °C. The best PLE conditions for MAC extraction (ethanol-water pH 2.0 [50% w/w]) resulted in 10.21 mg of malvidin-3-O-glucoside/g of dried grape marc (dr). Fifteen anthocyanins were identified and quantified in PLE extracts by UHPLC-UV-Vis. PLE with ethanol-water (50% w/w) as solvent at 100 °C achieved the highest TPC content (65.68 mg GAE/g dr) and antioxidant capacity by ORAC (772.11 μmol TE/g dr) and FRAP (1452 mg TE/g dr) among the evaluated conditions. Based on the results for extraction of monomeric anthocyanins and phenolics compounds, a sequential PLE process was performed and proved to be viable for the recovery of two different extract fractions.