Antioxidant Activities of Methanol Extract and Solvent Fractions of Marine Macroalga, Avrainvillea erecta (Berkeley) A. Gepp and E.S. Gepp (Dichotomosiphonaceae)

Purpose: To determine the antioxidant activity of methanol extract (ME) and solvent fractions of Avrainvillea erecta as well as their total phenolic and flavonoid contents.
Methods: The antioxidant activities of ME as well as its chloroform, butanol, and aqueous fractions (CF, BF and WF, respectively) of A. erecta were evaluated via 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and hydrogen peroxide (H₂O₂) scavenging assays as well as ferric reducing antioxidant power (FRAP) assay. Total phenolic and flavonoid contents were determined spectrophotometrically.
Results: CF and BF possessed equally high DPPH scavenging activity with half-maximal effective concentration (EC₅₀) of 535 and 532 mg/ml, respectively. CF had stronger NO scavenging activity (EC₅₀ 743 μg/mL) than ME and BF, although weaker compared with quercetin (EC₅₀ 279 μg/ml). CF also produced the highest FRAP value (451 μmol Fe²⁺/g) among all samples examined. Notably, H₂O₂ scavenging activity was only found in CF (EC₅₀ 387 μg/ml), which was as strong (p > 0.05) as that of gallic acid (EC₅₀ 456 μg/mL). BF had the highest total phenolic content while CF had the highest total flavonoid content.
Conclusion: CF of A. erecta, which has the highest flavonoid content of all the extracts evaluated, is a potential source of natural antioxidants, especially hydrogen peroxide scavengers.