Ultrasound-assisted ternary temperature-responsive deep eutectic solvents for extraction of carotenoids from tomato samples

As new green solvents, the low volatility of deep eutectic solvents (DESs) limits their development in natural product extraction. In this work, a series of novel lower critical solution temperature (LCST) type temperature-responsive DESs (TRDESs) were prepared and applied to the extraction of carotenoids from tomato. The highest yields (408.85 ± 4.97 μg/g of lycopene, 68.78 ± 2.00 μg/g of β-carotene) were obtained under the following conditions: extractant DES-16 (methyl 1-benzylpiperidine-4-carboxylate: valeric acid: heptanoic acid = 2:1:1), solid-liquid ratio 1:58 g/mL, extraction temperature 68 °C, and extraction time 44 min. Utilizing the temperature response characteristics of TRDESs, the separation of carotenoids and TRDESs was achieved in a mild way. Upon analysis, hydrophilic polysaccharides were simultaneously extracted and retained in water through the recovery experiment. Green Analytical Procedure Index (GAPI) proved the greenness of the method. This work provides new ideas for DESs in the extraction of natural products.