Optimization of microwave-assisted extraction (MAE) of coriander phenolic antioxidants - response surface methodology approach

BACKGROUND Microwave‐assisted extraction (MAE) of polyphenols from coriander seeds was optimized by simultaneous maximization of total phenolic (TP) and total flavonoid (TF) yields, as well as maximized antioxidant activity determined by 1,1‐diphenyl‐2‐picrylhydrazyl and reducing power assays. Box–Behnken experimental design with response surface methodology (RSM) was used for optimization of MAE. Extraction time (X1, 15–35 min), ethanol concentration (X2, 50–90% w/w) and irradiation power (X3, 400–800 W) were investigated as independent variables. Experimentally obtained values of investigated responses were fitted to a second‐order polynomial model, and multiple regression analysis and analysis of variance were used to determine fitness of the model and optimal conditions. RESULTS The optimal MAE conditions for simultaneous maximization of polyphenol yield and increased antioxidant activity were an extraction time of 19 min, an ethanol concentration of 63% and an irradiation power of 570 W, while predicted values of TP, TF, IC50 and EC50 at optimal MAE conditions were 311.23 mg gallic acid equivalent per 100 g dry weight (DW), 213.66 mg catechin equivalent per 100 g DW, 0.0315 mg mL−1 and 0.1311 mg mL−1 respectively. CONCLUSION RSM was successfully used for multi‐response optimization of coriander seed polyphenols. Comparison of optimized MAE with conventional extraction techniques confirmed that MAE provides significantly higher polyphenol yields and extracts with increased antioxidant activity. © 2016 Society of Chemical Industry