Deep eutectic solvent-based ultrasound-assisted extraction of polyphenols from Cosmos sulphureus.

In this study, deep eutectic solvents-based ultrasound-assisted extraction (DES-UAE) was done for extraction of polyphenols from Cosmos sulphureus. Among seven kinds of DESs prepared, choline chloride-lactic acid (1:2) was considered as a good candidate for polyphenols extraction due to superior extraction performance. Subsequently, process parameters for DES-UAE were optimized by response surface methodology. The highest total polyphenolic content (TPC) was achieved at 47.5 °C temperature, 32.6% water content and 4.0 W/mL ultrasonic energy density. This was 21% higher than that acquired with conventional ethanol-based UAE. Furthermore, Pearson's correlation coefficient revealed high correlation between TPC and antioxidant activity of extracts (r = 0.85). Moreover, HPLC analysis indicated that the substitution of DES for ethanol in UAE can effectively improve the individual concentrations in extracts of interested polyphenols (chlorogenic acid, caftaric acid, rutin and kaempferol) in the range of from 10.7% to 43.5%. In conclusion, this study implies that DES-UAE...