The antioxidant activities of methanol extract and its solvent fractions (n -hexane, dichloromethane and ethyl acetate) of three red seaweeds (Hypnea musciformis , H. valentiae , and Jania rubens ) collected from the Gulf of Mannar of South eastern coast of India were evaluated, using different in vitro systems, viz., DPPH, ABTS, HO radical scavenging activities, H 2 O 2 scavenging ability, Fe 2+ ion chelating ability and reducing potential. Folin-Ciocalteu method was used to determine the total phenolic content of the extracts/fractions, and the results were expressed as mg of gallic acid equivalent (GAE)/g of the seaweed extracts/ fractions. Thiobarbituric acid-reactive substances (TBARS) inhibition assay was employed to assess the ability of the seaweed extracts/fractions to inhibit lipid oxidation. Ethyl acetate (EtOAc) fractions of H. musciformis exhibited significantly higher total phenolic content (205.5 mg GAE/g), DPPH· scavenging activity (IC 50 0.6 mg/mL), ABTS .+ scavenging activity (IC 50 0.51 μg/mL), Fe 2+ chelating ability (IC 50 0.70 mg/mL), H 2 O 2 scavenging activity (IC 50 0.39 mg/mL), reducing ability (Abs 700 nm 1.46) and lipid peroxidation inhibitory ability (2.71 MDAEC/kg) (P <0.05) compared to its n-hexane, DCM fractions, crude MeOH extract and MeOH extracts/fractions of H. valentiae and J. rubens. DCM fraction of J. rubens showed significantly higher hydroxyl radical scavenging activity (IC 50 0.55 mg/mL) compared with H. musciformis and H. valentiae (P <0.05). This study indicated the potential use of red seaweeds, in particular, H. musciformis as candidate species to be used as food supplement for increasing the shelf-life of food industry, and candidates in combating carcinogenesis and inflammatory diseases.

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