Optimization of microwave-assisted extraction conditions for antioxidant compounds from Undaria pinnatifida using response surface methodology

CATARINA LOURENÇO-LOPES; CECILIA JIMENEZ LÓPEZ; LUCÍA CASSANI; PAULA GARCÍA-OLIVEIRA; ANTÍA G. PEREIRA; MARIA FRAGA; ANDREA GOMEZ-ZAVAGLIA; MIGUEL A. PRIETO; JESUS SIMAL GÁNDARA

Coimbra

Conferencia; International conference- Advances in the role of phenols in health effects and other uses; 2020

Iberphenol

Algae are a rich source of diverse secondary metabolites such as phenolic compounds and carotenes with health-related benefits. These compounds have attracted special attention in both, scientific and industrial fields, since they could be included into nutritional supplements for prevention and treatment of a wide variety of pathologies. In this way, the aim of this study was to simultaneously optimize the total phenolics content (TPC), total flavonoids content (TFC), extraction yield (EY), DPPH radical scavenging activity (DPPH), trolox equivalent antioxidant capacity (TEAC) and β-Carotene bleaching activity (BC) from Undaria pinnatifida using microwave-assisted extraction. To carry this out, response surface methodology (RSM) with a five-level central composite design combining the independent variables of ethanol concentration (0-100%), time (3-25 min) and pressure (2-20 bar) in 28 experiments was applied. Each response was individually optimized and compared with a global optimization that allowed obtaining the optimum extraction conditions which maximize allresponses at the same time. Analysis of variance of each response variable model showed that they were all significant (p < 0.05), suggesting that these models could be used to describe the effects of the selected independent variables on TPC, TFC, EY, DPPH, TEAC and BC of Undaria pinnatifida. The optimum conditions for extracting bioactive compounds with antioxidant activity from the studied alga were: 10.25±0.34 min, 20.00 ± 4.00 bar and 0% of ethanol, which means that water was more receptive polar solvent for microwave energy absorption than ethanol. In a next step, a validation study was performed and a close agreement between experimental and predicted values was observed, indicating the suitability of the model employed and the success of RSM in modelling responses to characterize their dependence with extraction conditions under evaluation. In conclusion, an aqueous microwave-assisted extraction (20 bar, 10 min) appears to be the optimum processing approach for the extraction of polyphenols with antioxidant activity from Undaria pinnatifida with no need for the use of organic solvents.