Extraction of Lycium barbarum polysaccharides using temperature-switchable deep eutectic solvents: A sustainable methodology for recycling and reuse of the extractant

Due to the nonvolatility of deep eutectic solvents (DESs), the recycling and reuse of them is encountering a lot of problems in the extraction and separation field. In this study, temperature-switchable DESs (TS-DESs) were prepared and their temperature-responsive characteristics and phase diagram were studied. TS-DESs were further used as the recyclable extractants for extracting Lycium barbarum polysaccharides (LBP) below their lower critical solution temperature (LCST), and then they can be recovered from the extract above their LCST. The main factors influencing the extraction process were investigated in the single-factor experiments. A maximal extraction yield of 465 mg/g was obtained. The TS-DES was recovered and reused in recycling experiments. The recovery of TS-DES was 80.2 % after the fifth cyclic test. The obtained LBP was studied by determining its molecular weight, assessing its radical scavenging activity, and analyzing its monosaccharide constituents. This study presents a novel method for polysaccharide extraction, which can also provide guidance for bioactive compounds extraction using recyclable extractants.