Extraction of curcumin from turmeric residue (Curcuma longa L.) using deep eutectic solvents and surfactant solvents
Using waste materials to extract biologically active ingredients with green solvents is a new trend for sustainable development. Herein, different types of deep eutectic solvents (DESs) and surfactant solvents (SSs) were used to extract curcumin from turmeric residues (TRs), among which choline chloride–propylene glycol (ChCl–Pro) showed the highest yield. The optimized extraction conditions included a ChCl : Pro ratio of 1 : 2, water content in the DESs of 20%, solid : liquid ratio of 1 : 40 maintained for 60 min at 50 °C, and a TR particle size of 0.18 mm. The extraction yield was 54.2 mg g−1, which was 1.31 times higher than when methanol was used as a solvent. Distilled water was used to recover curcumin from the DES extract with a recovery yield of 99.7%. Furthermore, the antioxidant and acetylcholinesterase (AChE) inhibitory activities of the recovered curcumin were evaluated, with IC50 values of 25.58 ± 0.51 and 19.12 ± 0.83 μg mL−1, respectively. This study highlights the promising potential of using green solvents to extract bioactive compounds from waste materials.