This is the first report of the interaction between these algal extracts, rich in natural compounds with antioxidant potential, and Gram positive and Gram negative bacterial cells.

Natural antioxidants found in marine macroalgae are bioactive compounds known to play an important role in the prevention of diseases associated with aging cells protecting them against the oxidative damage. The purpose of this study was to evaluate the antioxidant and cytotoxic activity of ethanolic extracts of two species of red seaweeds, Amansia multifida and Meristiella echinocarpa. In vitro antioxidant activity was determined by DPPH radical scavenging assay, ferric-reducing antioxidant power (FRAP) assay, ferrous ion chelating (FIC) assay, β-carotene bleaching (BCB) assay and total phenolic content (TPC) quantification. Cytotoxicity was evaluated with the brine shrimp Artemia sp. lethality test. The TPC values observed in the present study indicated that both species A. multifida and M. echinocarpa are rich in phenolic compounds, reaching values of 45.40 and 28.46 mg gallic acid equivalent (GAE) g -1 of ethanolic extract, respectively. DPPH radical scavenging and ferrous ion chelating showed values of 60% and 17%, respectively. Both seaweed extracts inhibited β-carotene oxidation by approximately 40%. None of the algal extracts were potentially cytotoxic. The results have showed that extracts of both species of marine red algae exhibit antioxidant potential and low toxicity. They are sources of natural antioxidant compounds.

Marine invertebrates are capable of synthesizing bioactive compounds, which may be beneficial to human health. The aim of this study was to evaluate the antioxidant, hemolytic, antimicrobial and cytotoxic activities of crude extract (70% EtOH), and dichloromethane (DCM), ethyl acetate (EtOAc), and aqueous (Aq) fractions of the marine zoanthid Palythoa caribaeorum. The phenolic compound contents of the crude extract, DCM, EtOAc and Aq fractions were 12.33, 18.17, 10.53, and 3.18 mg GAE per gram, respectively. DPPH radical scavenging activity showed slight variation. IC 50 of crude extract, DCM, EtOAc and Aq fractions were 11.13, 11.25, 11.74, and 11.28 µg mL -1 , respectively. Among the sample, ferrous ion chelating was the highest in crude extract (IC 50 302.90 µg mL -1 ), followed by EtOAc, Aq, and DCM fractions with 457.77, 547.91, and 641.82 µg mL -1 , respectively. Ferric-reducing antioxidant power showed optical density at about 0.5. The samples tested exhibited low hemolytic activity under 10% up to a concentration of 50 μg mL -1 . No antimicrobial activity was observed against any of the tested bacterial strains. For the cytotoxic activity, LC 50 of DCM, crude extract, EtOAc, and Aq were 52.10, 83.06, 86.34, and 117.45 μg mL -1 , showing high toxicity.

This study evaluated the chemical composition and antioxidant activity of fatty acids from the marine red algae Pterocladiella capillacea (S. G. Gmelin) Santelices & Hommersand 1997 and Osmundaria obtusiloba (C. Agardh) R. E. Norris 1991. The gas chromatography mass spectrometry (GC-MS) identified nine fatty acids in the two species. The major fatty acids of P. capillacea and O. obtusiloba were palmitic acid, oleic acid, arachidonic acid and eicosapentaenoic acid. The DPPH radical scavenging capacity of fatty acids was moderate ranging from 25.90% to 29.97%. Fatty acids from P. capillacea (31.18%) had a moderate ferrous ions chelating activity (FIC), while in O. obtusiloba (17.17%), was weak. The ferric reducing antioxidant power (FRAP) of fatty acids from P. capillacea and O. obtusiloba was low. As for β-carotene bleaching (BCB), P. capillacea and O. obtusiloba showed a good activity. This is the first report of the antioxidant activities of fatty acids from the marine red algae P. capillacea and O. obtusiloba.

ABSTRACT. The aim of the present research was to evaluate the antioxidant activity of six species of marine algae (Caulerpa cupressoides, Ulva fasciata, Amansia multifida, Cryptonemia crenulata, Dictyota dichotoma and Sargassum vulgare) collected in 2011 at Paracuru Beach, Ceará State, Brazil. Methanol extracts were prepared from oven-dried algae and used to measure total phenolic content (TPC) using the FolinCiocalteu colorimetric method. In vitro antioxidant activity of the algal extracts (12.5 to 100 μg mL ). These results allow us to consider the algae species studied as potentially promising sources of natural antioxidants. ). Estes resultados permitem considerar as espécies de macroalgas estudadas como fontes potencialmente promissoras de antioxidantes naturais.Palavras-chave: extratos algáceos, compostos fenólicos, estresse oxidativo, antioxidantes naturais.