Process optimization of deep eutectic solvent-based microwave-assisted extraction of flavonoids from Ziziphi Spinosae Semen using response surface methodology

Total flavonoids were extracted from Ziziphi Spinosae Semen (ZSS) by applying microwave-assisted extraction with low eutectic solvent (DES) as the extractant. This study investigated the effect of 21 different components of DES on the yield of total flavonoids in ZSS. The results revealed that the DES system, which consists of choline chloride and lactic acid with a molar ratio of 2:1, achieved the best flavonoid extraction efficiency. Based on the single-factor test, response surface methodology was used to optimize and determine the optimal process conditions for the extraction of total flavonoids from ZSS with deep eutectic solvent. The maximum flavonoids yields were achieved at 36.24 mg/g within the 50% DES water content, a microwave power of 600 W, a microwave time of 60 s, a liquid-solid ratio of 1:28 mg/mL, an extraction time of 66 min, and an extraction temperature of 93 °C. The macroporous resin was used to recover flavonoids from extracts. The DM130 resin showed higher adsorption/desorption performance. The total flavonoids of ZSS were extracted using the recovered DES with a yield of 32.58 mg/g and a high reusability of 89.9%.