An analysis of the supercritical fluid extraction process on Helianthus annuus L (sunflower) using carbon dioxide and water on a pilot plant scale has been carried out. The possibility of using the resulting extract as an herbicide was analyzed by bioassays. The influence of time for different solvent flow rates was investigated. The extraction pressure and temperature were optimized in previous studies and a pressure of 380 bar and a temperature of 50 degrees C were selected. The bioactivities and extraction yields obtained under the different conditions were compared. The best activity profiles were obtained for 40 g/min CO2 + 1 g/min H2O and 80 g/min CO2 + 2 g/min H2O. (C) 2008 Elsevier B.V. All rights reserved.