Natural bioactive chemicals extracted from Calendula officinalis using efficient binary deep eutectic solvent system

• Binary system of deep eutectic solvents (DES) selectively extracts natural bioactives. • DES extract bioactive substances from plants more effectively than classic solvents. • Switchable DES enable easy separation of carotenoids from Calendula officinalis. • Marigold extracts are reach in rutin, chlorogenic acid, and hesperidin. • DES can be regenerated and applied in the subsequent extraction cycles. The use of deep eutectic solvents (DESs) for extracting bioactive compounds from biomass is gaining attention due to their high efficiency and ecological character. However, separating the isolated biomolecules from DESs is challenging, which has led to increased interest in switchable hydrophobic deep eutectic solvents (HDESs). This study explored the extraction of bioactive compounds from Calendula officinalis petals using DESs and HDESs under various conditions. The results showed that DESs were efficient for phenolics and flavonoids extraction (16 mg/g and 12 mg/g respectively), while HDESs were better for carotenoids (2.2 mg/g). The main components in the extracts were rutin, chlorogenic acid, and hesperidin. Furthermore, a binary system of HDES + DES enabled simultaneous extraction of compounds with different polarities and easier separation of carotenoids. The basket reactor was generally less effective than the stirred batch reactor for polyphenols extraction in the binary system.