Abstract
The potential of antioxidant activity of the green algae (Chaetomorpha sp.) was studied in this work. The optimum processing conditions for the extraction of antioxidant compounds from dried green algae were determined using response surface methodology (RSM). A central composite design (CCD) was applied to determine the effects of three process variables as follows: solvent concentration (percent), extraction time (min) and microwave power (w) on total phenolic contents, ferric reducing power, 2'2-dipheny-l-picrylhydrazyl (DPPH) radical scavenging activity and total antioxidant capacity assays. The independent variables were coded at five levels and CCD included 20 experimental runs with six replications at the center point. The statistical analysis of data was performed using design expert software and second-order polynomial models generated after analysis of variance (ANOVA) applied for predicting the responses. The results revealed that the highest total phenol content and reducing power were 1.09 and 0.12 mg of tannic acid equivalent/g dry weight, respectively. The maximum antioxidant activity was 0.19 mg ascorbic acid equivalent/g dry weight and DPPH was 99.8 % under MAE. The optimum conditions using RSM for the predicted responses were: microwave power 300 W, extraction time 8 min and solvent concentration 25 %, respectively. Furthermore the actual experimental values were adjacent to the corresponding predicted values which demonstrated fitness of the employed models and suitability of RSM in extraction parameters optimization.