Antioxidant potential of marine microalgae phenolic fractions

Microalgae are a potential renewable and sustainable source of biologically active compounds. Several biological activities have been attributed to different compounds such as phycobilins, fatty acids, vitamins, polysaccharides and sterols, namely phenolic compounds have been triggered special attention. The polyphenolic matrix obtained from marine algae exhibits a wide range of biological properties, e.g. antioxidant, anti-inflammatory, antidiabetic and anticancer. Therefore, the main goal of the present study was to evaluate the potential of the phenolic fraction of the marine microalgae Arthrospira, Raphidonema and Choridella sp., as new source of natural antioxidants. Acetone and methanolic fractions obtained from microalgae were quantified for their total phenolic content (TPC) analysis, by the Folin-Ciocalteu method. Afterwards, the extracts were also screened for their in vitro antioxidant activity using DPPH free radical-scavenging assay, iron chelation activity (ICA) and radical superoxide scavenging (SO). TPC content of Arthrospira is higher than Chloridella and Raphidonema for both fractions tested. Raphidonema and Chloridella, acetone fraction exhibited higher levels of phenolic compounds, compared to methanolic fraction. Regarding the in vitro antioxidant activity, acetone fractions showed the greatest ability for DPPH and superoxide scavenging assays and iron chelation. Specifically, acetone fraction of Arthrospira at 0.5 mg/mL had better ability to scavenge DPPH radicals (31.59 ± 1.21% of inhibiton) and also higher capacity for iron chelation (26.87 ± 2.18% of iron chelation) than Raphidonema and Chloridella. Overall, acetone solvents extraction was a better choice to improve antioxidant performance of extracts. Full characterization of antioxidant potential of marine microalgae fractions is ongoing with cellular models to assess bioactivities and consequently contribute to marine microalgae valorization.The authors acknowledge the financial support provided by the FCT-Portuguese Foundation for Science and Technology (PD/BD/150264/2019), under the Doctoral Programme “Agricultural Production Chains – from fork to farm” (PD/00122/2012), and the Financiamento Plurianual de Unidades de I&D UIDB/04050/2020. This work was also supported by project “EXTRATOTECA - Extratos de microalgas com elevado valor acrescentado” co-financed by FEDER under COMPETE 2020