The possibility of recovering biologically active polyphenolic compounds from hydro-alcoholic mixtures, with supercritical carbon dioxide, was investigated. In order to evaluate the viability of this fractionation step, vapor-liquid equilibrium measurements on the quaternary systems (CO2 + ethanol + water + phenolic compound = resveratrol, p-coumaric acid, quercetin-3-glucoside, and catechin) were performed at 40 degrees C and at (15 and 20) MPa. The separation factors for hydro-alcoholic mixtures of different compositions in water + ethanol were determined and compared.