Antioxidant activity of supercritical extracts from Nannochloropsis gaditana: Correlation with its content of carotenoids and tocopherols

• Minor lipids content and antioxidant activity were studied under a response surface design.
• High temperature and CO2 density resulted in higher minor lipids content and antioxidant activity.
• Extraction temperature had an effect higher than CO2 density on studied responses.
• Antioxidant activity positively correlated with the minor lipids content in microalga oil.
• Fatty acid composition was measured in selected supercritical extract from Nannochloropsis gaditana.
• No previous studies have reported on supercritical extraction from pelletized microalgae.

Nannochloropsis gaditana is a microalga characterized by its high lipid content and as an important source of carotenoids, recognized as potent natural antioxidants. The objective of this work was to study the effects of temperature (36–64 °C) and CO2 density (914–956 kg/m3) on the content of carotenoids and tocopherols (minor lipids), and the antioxidant activity of oil extracted from N. gaditana using supercritical CO2. Antioxidant activity was measured by the DPPH assay, FRAP assay and β-carotene bleaching assay. A process development unit was used for extraction experiments, performed under a central composite rotatable design. The experimental data were analyzed by means of the response surface methodology. Content of carotenoids and tocopherols showed differences of 1.5- and 2.3-fold, respectively. The minor lipid content and the antioxidant activity increased with the increase of the temperature and CO2 density, reaching the highest values at 64 °C and 956 kg/m3 for all responses studied. Important antioxidant properties in the oil showed a positive correlation with the content of minor lipids.

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