Study of the potential of two red algae extracts against oxidative stress. Optimisation and quantification of antioxidant compounds

Abstract

Oxidative stress occurs when there is an imbalance between the action of free radicals (ROS) and endogenous enzymatic antioxidants, causing oxidative damage at cellular level (Grande et al., 2006). Therefore, in these situations, it is necessary to apply exogenous antioxidants (Machu et al., 2015). Seaweeds are a natural source of these compounds, their antioxidant capacity is mainly due to the presence of active biomolecules, which could be beneficial in the treatment of cellular damage caused by oxidative stress (Sánchez-Bonet et al., 2021; Yalçın et al., 2021). The objective of this study was therefore to obtain crude extracts from the red algae: Palmaria palmata and Porphyra sp, and characterize their composition by means of chromatographic techniques. To obtain extracts with the highest antioxidant activity, UAE extraction was used and the variables optimised were: quantity of algae, type, volume and concentration of solvent, timepower and temperature. Optimal extraction conditions were: 8 g of algae, 20 mL of ethanolwater (40:60), 10 min-300 W and 65 °C for P. palmata and 35 °C for Porphyra sp. Antioxidant activity was determined by the DPPH method, obtaining better results for Porphyra sp. than Palmaria palmata (87.64% vs. 78.70%, respectively). These results were confirmed by ORAC and FRAP assays. In addition, the total content of polyphenols (Folin- Ciocalteu) and polysaccharides (Dubois) of the optimised extract were determined. Lastly, by means of HPLC-DAD, the polyphenol content was determined by quantifying 11 polyphenols in Palmaria palmata and 10 in Porphyra sp. And, by means of HPLC-Fl, the the pigments: fucoxanthin, violaxanthin, lutein and chlorophyll a' in Palmaria palmata, and lutein and chlorophyll a' in Porphyra sp. were identified and quantified. The results obtained confirm the high potential of Palmaria and Porphyra algae in the possible treatment of oxidative stress.