Allelopathic properties of the fractions obtained from sunflower leaves using supercritical carbon dioxide: The effect of co-solvent addition

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