Optimization of the Ultrasound‐Assisted Extraction of Phenolic Antioxidants from Cistus Salvifolius L. Using Response Surface Methodology

Abstract The current work aims to optimize the ultrasound‐assisted extraction (UAE) of Cistus salviifolius L. (aerial parts) antioxidative phenolic compounds using response surface methodology. A Box–Behnken design has been conducted to investigate the effect of four factors, namely: (i) percentage of ethanol (50–90 %, v/v), (ii) temperature (40–80 °C), (iii) solvent‐solid ratio (10–50 mL g −1 ) and (iv) extraction time (5–25 min) on four responses, namely: total phenolic content (TPC), total flavonoid content (TFC) 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical inhibition, and ferric reducing antioxidant power (FRAP). Based on the desirability index, UAE with 50 % (v/v) ethanol, at 80 °C, using a solvent‐solid ratio of 32.24 mL g −1 , for 21 min resulted in the maximum recovery of phenolic antioxidants. Under optimum conditions, the experimental values of TPC, TFC, % DPPH radical scavenging activity, and FRAP were 171.67±4.69 mg GAE g −1 , 26.87±0.78 mg CE g −1 , 81.31±0.16 %, and 1038.22±7.69 μmol TE g −1 , respectively. Results shows a reasonable agreement of experimental values with the predicted ones; the absolute error values being in all cases lower than 2.90 %. The present work provide a developed eco‐friendly extarction method that is appropriate for the improved recovery of phenolic antioxidants from C. salviifolius L.