Sustainable ultrasound-assisted extraction of osthole from Cnidum monnieri (L.) Cuss based on natural deep eutectic solvents and switchable hydrophilicity solvents

Osthole, a compound found in Cnidum monnieri (L.) Cuss has various pharmacological activities. Ultrasound-assisted extraction of osthole was conducted using natural deep eutectic solvents (NADESs) combined with switchable hydrophilicity solvents (SHSs), and the feasibility of repeated use of recycled extractants was evaluated. NADES (xylose-levulinic acid) was used as an extraction solvent for the green extraction of osthole from Cnidum monnieri (L.) Cuss. Osthole in NADES was finally enriched in heptanoic acid, and due to the heptanoic acid convertibility, osthole can be easily and rapidly isolated and recovered. By adjusting the pH to alkaline, hydrophobic heptanoic acid was switched into a hydrophilic solution to precipitate the osthole. The recovery of osthole was over 90 %, with a yield of 8.35 mg g –1 . After five reuses of recycled NADES to extract new Cnidum monnieri (L.) Cuss powder, the change in osthole yield was non-significant. This novel, eco-friendly, and sustainable extraction method offers a new idea for developing bioactive substances in medicinal plants.