Extraction and purification of grape seed polysaccharides using pH-switchable deep eutectic solvents-based three-phase partitioning.

T-butanol is widely used in three-phase partitioning (TPP), which is harmful to the environment. pH-switchable deep eutectic solvents (DESs) can be used as recyclable alternatives to t-butanol. This study aimed to construct DES-based TPP for extracting and purifying grape seed polysaccharides (GSP). The main influence factors were investigated in single-factor experiments. DES-1 (dodecanoic acid: octanoic acid = 1:1)-based extraction was screened, and the extraction yield reached the maximum of 98.04 mg/g under the optimal conditions. Furthermore, DES can be recycled, only suffering a small loss capacity in extraction yield after 25 cycles. Most importantly, the extractability of DES could be completely recovered after switching and regeneration. The molecular weight of obtained GSP was 60 kDa, and the main monosaccharides of GSP included mannose, glucose, galactose, and arabinose. This study provides an efficient and sustainable method for the extraction of bioactive substances.