Optimization of antioxidant extraction from edible brown algae Ascophyllum nodosum using response surface methodology

•Antioxidant extraction from algae Ascophyllum nodosum was optimized.•Three variables of a water–ethanol solvent system were studied.•The condition for maximum antioxidant activity was determined.•The condition for the highest crude extract yield was predicted.•Both quadratic models show good agreement with validation results.