Abstract— <p>A comparison of thermal and ultrasonic intensification of supercritical fluid extraction using wild parsnip seeds, a source of plant oil and furocoumarin photosensibilizers, is conducted. It is found that, even at pressure as high as 300 bar, the temperature effect on parsnip extraction demonstrates a so-called retrograde behavior; i.e., isobaric temperature increase leads to a decrease in extraction speed and overall mass yield. The previously proposed idea on a chromatography-like mechanism of the supercritical fluid extraction process with multiple re-adsorption of the isolated components onto the plant material working as a sorbent allows explaining the observance of retrograde behavior, uncommon for such high pressure values. The overall influence of ultrasonic intensification of extraction process is shown to be similar to that of temperature. At low extraction pressure (100 bar), when cavitation of a subcritical fluid entering the extraction zone is possible in principle, ultrasonication leads to an increased extraction kinetics at the initial, linear part of the extraction curve. At high working pressure (300 bar), the effect of ultrasonication is essentially equal to that of direct heating. Using supercritical fluid chromatography, the furocoumarin profiles of the thermal and ultrasonic parsnip extracts are shown to be identical; thus, ultrasonication even at 100 bar does not cause any unwanted sonochemical effects.</p>