Sequential Extraction of Bioactive Polar and Non-Polar Compounds from Calendula Using Supercritical Fluid Extraction (SFE) and Natural Deep Eutectic Solvents (NaDESs)

Sequential selective extraction of bioactive compounds from plants can be achieved by using different approaches. Recently, we described the use of supercritical fluid extraction (SFE) to provide two fractions from Calendula flower, one containing the faradiol esters, in a non-polar fraction, and one the isorhamnetin-3-O-rutinoside (narcissin), in a polar fraction. In this paper, we attempted to replace the second step of SFE with NaDES (natural deep eutectic solvent) ultrasonic-assisted extraction (UAE) since NaDES extract could be directly incorporated into cosmetic formulation owing to their safety. The paper reports the method development for the UHPLC analysis of viscous NaDES samples, the screening of the suited NaDES from narcissin extraction and the Box–Behnken experimental design applied to the Calendula flower to select the experimental conditions—ultrasound frequency, water content, and extraction duration—that maximize narcissin recovery. Finally, a sequential selective extraction methodology combining SFE with the NaDES is proposed and discussed.