Extraction of bioactive phenolics from black poplar (Populus nigra L.) buds by supercritical CO 2 and its optimization by response surface methodology.

The scope of current study was to apply supercritical CO2 for extraction of black poplar buds (Populus nigra L.) and to optimize the extraction parameters (pressure and temperature) using response surface methodology aimed at maximum extraction yield, total phenolic content (TP), ferric reducing antioxidant power (FRAP) and individual amount of selected bioactive phenolics. The pressure and temperature influenced significantly the extract yield (0.38-10.28 g/100 g), TP content (21.62-31.09 μg GAE/mg), FRAP capacity (0.30-0.48 μmol Fe2+ /mg), and the amounts of p-coumaric acid (0.33-1.52 μg/mg), pinocembrin (20.99-47.24 μg/mg) and galangin (4.04-10.25 μg/mg). The extraction of pinostrobin (51.73-79.56 μg/mg), pinobanksin (0.41-1.55 μg/mg), and chrysin (0.97-2.03 μg/mg) was significantly affected only by the operating pressure. Optimized extraction parameters (30 MPa and 60 °C) allow to obtain higher yield and extracts enriched with bioactive phenolics.