The use of supercritical carbon dioxide (SC-CO2), with water as a modifier, was evaluated in this study as a method to extract protocatechuic acid (PA) from Scutellaria barbata D. Don. The highest extraction yield of PA, 64.094 +/- 2.756 mu g/g of dry plant, was achieved at 75 degrees C and 27.5 MPa, with the addition of 15.6% (v/v) water as a modifier. The mean particle size was 0.355 mm, the CO2 flow rate was 2.2 mL/min (STP) and the dynamic extraction time was 100 min. At pressures of 16.2-30.0 MPa and temperatures of 45-75 degrees C, the mole fraction solubilities of PA in SC-CO2 ranged from 2.829 x 10(-7) to 9.631 x 10(-7). The solubility data for PA fit well in the Chrastil model. It is evident that the SC-CO2 extraction uses less solvent, saves both energy and time and is an environmentally friendly extract technology that can be used in the food, cosmetic and pharmaceutical industries. (C) 2013 Elsevier B.V. All rights reserved.