Optimization of Ultrasonic-Assisted Deep Eutectic Solvent Extraction Process, Biological Activities and Components of Burdock Polyphenols

The extraction effects of six deep eutectic solvents on burdock polyphenols (BPs) were investigated, and the response surface methodology was used to optimize the process conditions of ultrasonic-assisted deep eutectic solvent extraction of BPs, moreover, the total reducing power, the DPPH• scavenging capacity, the inhibition of α-glucosidase and cholic acid binding capacity in vitro were studied, and its composition were analyzed by HPLC. The results showed that DES 5 (the molar ratio of choline chloride to ethylene glycol was 1:4) was the best solvent system for the extraction of BPs. The optimum technological conditions were as follows, the water content of deep eutectic solvent was 40%, the ratio of material to liquid was 55:1 mg/mL, the extraction temperature was 49 ℃, and the extraction time was 41 min, under the above conditions, the yield of BPs was 1.19%±0.11%. The biological activity analysis showed that the IC₅₀ of the total reducing power and DPPH• scavenging capacity of burdock polyphenol were 0.93 mg/mL and 7.03 μg/mL, respectively, indicating that it had good antioxidant capacity, but weaker than V_C. The IC₅₀ of α-glucosidase inhibition was 0.13 mg/mL, which was higher than acarbose, indicating that it possessed excellent hypoglycemic activity. In addition, its cholic acid binding rate was 33.23% when the mass concentration was 1.5 mg/mL, implied that it had a certain hypolipidemic activity. HPLC analysis showed that BPs contained chlorogenic acid, caffeic acid and ferulic acid. The results would provide a theoretical basis for the green preparation of burdock polyphenol and its development and utilization as a functional component of antioxidation, hypoglycemia and blood lipids.