Switchable deep eutectic solvents for the extraction of phlorizin and trilobatin from sweet tea (Lithocarpus litseifolius (Hance) Chun)

Switchable deep eutectic solvents (SDESs) have recently been developed to improve the recovery and reuse of the extractants. In this work, temperature-induced SDESs were prepared and used for the extraction of flavonoids (representative phlorizin and trilobatin) from sweet tea (Lithocarpus litseifolius (Hance) Chun). These SDESs solution can switch between solution and sediment depending on the temperature, and the phase diagram of SDESs solution had been drawn. Their temperature-responsive characteristics were studied by various characterizations, including variable-temperature FT-IR, variable-temperature ¹H NMR, and variable-temperature dynamic light scattering (DLS). SDES-1 (Benzamide: Malic acid = 2:1) was screened as the optimal extractant, and the major factors affecting the extraction process were studied by single-factor experiments and optimized by response surface methodology (RSM). The extraction yields for phlorizin and trilobatin were 114.72 and 12.56 mg/g, respectively. Moreover, the recoveries for phlorizin and trilobatin reached 98.46 % and 94.64 %, respectively. This study thus provides an environmentally sound strategy for extracting bioactive compounds from plant resources.