Measurement of Antioxidant Activities and Phenolic and Flavonoid Contents of the Brown Seaweed Sargassum horneri: Comparison of Supercritical CO₂ and Various Solvent Extractions

Seaweed Sargassum horneri extracts were obtained using supercritical carbon dioxide (SC-CO2) and different solvents. SC-CO2 was kept at a temperature of 45oC and pressure of 250 bar. The flow rate of CO 2 (27 g/min) was constant during the entire 2-h extraction period, and ethanol was used as a cosolvent. Six different solvents [acetone, hexane, methanol, ethanol, acetone mix methanol (7:3), and hexane mix ethanol (9:1)] were used for extraction and agitated by magnetic stirring (250 rpm) in the dark at 25oC for 20 h; the ratio of material to solvent was 1:10 (w/v). Antioxidant properties of S. horneri extracted using SC-CO2 with ethanol and different solvents have shown good activity. The highest activity belongs to SC-CO2 with ethanol extracted oil, showing DPPH, ABTS, total phenolic content, and total flavonoid levels of 68.38 ± 1.21%, 83.51 ± 1.25%, 0.64 ± 0.02 mg/g, and 5.57 ± 0.05 mg/g, respectively. The S. horneri extracts showed a significant correlation between the antioxidant activity and phenolic content. Based on these results, the SC-CO2 extract (ethanol) of the seaweed extract from brown seaweed may be a valuable antioxidant source.