The demand for antioxidants in the food and supplement industries has increased significantly over the past decade, with microalgae emerging as a promising natural source. This study evaluated the antioxidant activities of five species of commercial microalgae. Antioxidants were extracted from Arthrospira platensis, Chlorella vulgaris, Dunaliella salina, Haematococcus pluvialis, and Nannochloropsis salina by lysing the cells with a sonicator and using acetone, ethanol, methanol, and hexane as solvents. Antioxidant activity was assessed using ferric reducing power, ferrous chelating activity, and ABTS radical scavenging activity assays. Methanol appeared to be the most effective solvent for extracting antioxidants from microalgae. N. salina exhibited the highest ferric reducing power (190.8 µmol ascorbic acid equivalent/g), followed by A. platensis (182.8 µmol ascorbic acid equivalent/g), C. vulgaris (154.9 µmol ascorbic acid equivalent/g), H. pluvialis (138.0 µmol ascorbic acid equivalent/g), and D. salina (119.9 µmol ascorbic acid equivalent/g). A. platensis demonstrated the highest ferrous chelating activity (171.0 µmol EDTA equivalent/g), followed by C. vulgaris (135.4 µmol EDTA equivalent/g), N. salina (95.6 µmol EDTA equivalent/g), D. salina (36.9 µmol EDTA equivalent/g), and H. pluvialis (6.6 µmol EDTA equivalent/g). In ABTS radical scavenging activity, A. platensis showed the highest activity (56.8 µmol Trolox equivalent/g), followed by H. pluvialis (23.4 µmol Trolox equivalent/g) and C. vulgaris (21.9 µmol Trolox equivalent/g), while D. salina and N. salina showed no ABTS radical scavenging activity. Interestingly, D. salina displayed the lowest antioxidant activities among all tested species, despite being known as the riches natural source of β-carotene. The low antioxidant activity of D. salina could be attributed to the oxidation of β-carotene during storage, as indicated by the visible fading of its orange color. This study highlights the considerable variability in antioxidant activities among different microalgae species and emphasizes the importance of selecting appropriate extraction methods.

Daniel Norena-Caro

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