Modelling and optimization of radical scavenging activity of Eryngium caucasicum Trautv leaf extracts obtained by ultrasound assisted extraction

Response surface methodology is a collection of mathematical and statistical techniques for empirical model building. In this study, response surface methodology based on Box Behnken design was applied for investigation, optimization and modelling of ultrasound assisted extraction independent variables including amplitude (25, 50 and 75%), temperature (30, 45 and 60 ºC) and sonication time (20, 40 and 60 min) to maximize the radical scavenging activity of Eryngium caucasicum Trautv leaf extracts. The radical scavenging activity was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) radical scavenging activity methods. Based on results obtained linear, quadratic and interaction effects of three independent variables had significant effect on DPPH and H2O2 free radical scavenging activity. Quadratic polynomial model was obtained for each response using multiple linear regression analysis. By using numerical optimization the optimized condition was obtained as 50% amplitude, 42 ºC temperature and 51 min sonication time. The radical scavenging activity of extracts under these optimal conditions was predicted as 50.20% DPPH free radical scavenging activity and 26.55% H2O2 free radical scavenging activity. The models obtained for prediction of dependent variables has a good closeness with experimental results. Finally, the results obtained were compared with conventional Soxhlet extraction results. Based on the results, by applying ultrasound waves it is possible to obtain more compounds with radical scavenging activity during short time.