• Extracts from Lycium ruthenicum Murr. fruit were obtained by UAE. • Phenolic compounds and antioxidant activities of obtained extracts were simultaneously optimized by RSM. • Optimum parameters: time 30 min, power 100 W, solvent-sample ratio 40 mL/g, ethanol 33%. • The extracts contained phenolic acids, identified and quantified by HPLC.
Lycium ruthenicum Murr. (LR) is a functional food that plays an important role in anti-oxidation due to its high level of phenolic compounds. This study aims to optimize ultrasound-assisted extraction (UAE) of phenolic compounds and antioxidant activities of obtained extracts from LR using response surface methodology (RSM). A four-factor-three-level Box-Behnken design (BBD) was employed to discuss the following extracting parameters: extraction time (X 1), ultrasonic power (X 2), solvent to sample ratio (X 3) and solvent concentration (X 4). The analysis of variance (ANOVA) results revealed that the solvent to sample ratio had a significant influence on all responses, while the extraction time had no statistically significant effect on phenolic compounds. The optimum values of the combination of phenolic compounds and antioxidant activities were obtained for X 1 = 30 min, X 2 = 100 W, X 3 = 40 mL/g, and X 4 = 33% (v/v). Five phenolic acids, including chlorogenic acid, caffeic acid, syringic acid, p-coumaric acid and ferulic acid, were analyzed by HPLC. Our results indicated that optimization extraction is vital for the quantification of phenolic compounds and antioxidant activity in LR, which may be contributed to large-scale industrial applications and future pharmacological activities research.