Supercritical fluid extraction of phenolic compounds from Eucalyptus globulus Labill bark

The supercritical fluid extraction (SFE) of phenolic compounds from Eucalyptus globulus bark was carried out along with detailed analysis of the extracts for the first time. The extracts were accessed in terms of: (i) extraction yield (EY), (ii) total phenolic content by Folin-Ciocalteu method (TPC), (iii) phenolics quantified by high performance liquid chromatography (PC-HPLC), and (iv) antioxidant activity (AA). Preliminary runs were performed with pure and modified CO2, using ethanol (EtOH), ethyl acetate, and water. The CO2/EtOH mixture provided the best extraction yield, high total phenolic content and antioxidant activity. Results also demonstrated high selectivity of the CO2/EtOH mixture to the extraction of flavanones, particularly eriodictyol and naringenin; and to the O-methylated flavonol isorhamentin, also found in abundance. To analyse the influence of temperature, ethanol content and flow rate on SFE at 300 bar using CO2/EtOH, a full 2(3) design of experiments was accomplished. The most favourable conditions under the experimental range studied were found as 70 degrees C, 20% ethanol, and 10 g of CO2 min(-1), for which EY = 0.48%, TPC = 57.22 mg of gallic acid equivalents (GAE)g(-1) of extract, PC-HPLC = 119.46 mg g(-1) of extract, and AA = 49.74 mg of ascorbic acid equivalents (AAE)g(-1) of extract. (C) 2012 Elsevier B.V. All rights reserved.