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

Brown algae are valuable sources of health-benefiting compounds, such as polyphenols, proteins, and polysaccharides. In the present study, a binary solvent system of ethanol and water was used to obtain crude extracts from edible brown algae Ascophyllum nodosum. The extraction process was optimized using Box-Behnken design and response surface methodology to obtain crude extracts with strong antioxidant activity and high yield. Three variables including solvent-to-solid ratio (30-70 ml/g), ethanol concentration in the solvent system (40-80%), and extraction temperature (20-60 degrees C) were investigated to optimize the extraction process. The condition for maximum antioxidant activity of the crude extract was found at 70 ml/g solvent-to-solid ratio, 80% ethanol concentration, and 20 degrees C extraction temperature, while the condition for the highest crude extract yield was 40 mug solvent-solid-ratio, 44.83% ethanol concentration and 60 degrees C extraction temperature. Under the model-predicted optimal conditions, the predicted antioxidant activity and yield of the crude extract were 74.01 ml/g (1/IC50) and 55.60 mg extract/g-algae, which were in close agreement with the experimental results of 74.05 mug and 53.80 mg extract/g-algae, respectively, suggesting that the models could accurately predict and improve the extraction of antioxidants from A. nodosum. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.