Allelopathic properties of the fractions obtained from sunflowerleaves using supercritical carbon dioxide: The effect ofco-solvent additionZ

tThe work described here is a continuation of a previous study centered on the extraction, using super-critical carbon dioxide, of bioactive substances from sunflower leaves of the Helianthus annuus L. varietyArianna. In this study the addition of 9% of ethanol as co-solvent was analyzed. The extraction was carriedout (P = 100/400 bar, T = 35/55◦C, ethanol = 9%) in order to analyze the influence of pressure, temperatureand sample pre-treatment on the extraction yield and bioactivity of the extracts. The addition of 9% ofethanol to the supercritical solvent enhanced both the extraction yield and the biological activity of theextracts. The best conditions were a pressure of 400 bar and a temperature of 55◦C. In an effort to improvethe bioactivity of the extract, a cascade fractionation of the extracts was carried out and this gave differ-ent results in terms of biological activities and extraction yields. The phytochemical compositions of theextracts were analyzed by thin layer chromatography. The fractionation that gave the best results wascarried out at 90 bar and 40◦C in the first separator. Finally, the effect of extracts on the growth of seedsfrom different plants was analyzed