Switchable Deep Eutectic Solvents for the Green Extraction of Tea Saponins From Camellia Oleifera Seed Meal

Tea saponin has garnered tremendous interest for its potential use in surfactant and drug synthesis. This research was designed to develop a technique based on pH-responsive switchable deep eutectic solvents (SDESs) for extracting tea saponins from Camellia oleifera seed meal. SDES synthesized from hexanoic acid and triethanolamine (1:1 molar ratio) offered the optimum extractive performance and the optimal conditions were obtained through single-factor experiments: 30 wt% water content in SDES, solid-liquid ratio of 1:30 g/mL, 60°C extraction temperature, 30 min extraction time, and acid volume of 1500 µL. The extraction yield was 162.14 mg/g after optimization, which increased by 15.65% and 9.47% compared to water and ethanol extraction methods, respectively. After pH adjustment, 98.95% of the tea saponins were recovered in the bottom phase. After precipitation and freeze-drying procedures, the purity of the tea saponin solid was 62.9%.