Propriedades do extrato aquoso da macroalga verde (ulva lactuca leach).

Abstract

Ulva lactuca Leach, popularly known as "sea lettuce", is a green seaweed belonging to the Ulvaceae family. Macroalgae are considered efficient biofilters, as they absorb and store nutrients dissolved in the sea, improving water quality for aquatic life. There are reports of U. lactuca as a source of active metabolites with antimicrobial and hepatoprotective function, therefore, highlighting the need to investigate its use. This study aimed to investigate the aqueous extract of Ulva lactuca Leach, by determining its phenolic composition and biological activities, such as; antioxidant, cytotoxic, hepatoprotective and antimicrobial. For that, an aqueous extract of U. lactuca was prepared for the following assays: antioxidant activity determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) method; cytotoxic effect, viability of Artemia salina Leach nauplii; hepatoprotective effect, by measurement of liver biomarkers in gavage treated albino Winstar rats (Rattus norvegicus); and antimicrobial activity against bacterial strains of de Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella tiphy, by disk diffusion test. The results obtained showed that the aqueous extract of U. lactuca presents reasonable values of phenolic compounds, exhibiting 25 mEq of gallic acid/g in the tested sample. This value influences the antioxidant activity, which exhibited an inhibitory effect against the DPPH radical of approximately EC50 = 6, 82%. As for the hepatoprotective effect, apparently, the use of U. lactuca does not differ from the use of distilled water, since there was no significant difference when evaluating liver biomarkers (aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (FA) and bilirubin (BL)). As for the microbial susceptibility test, the aqueous extract did not show activity against the previously mentioned strains. Lastly, the toxicity assay showed mean LD50 values of approximately 13,564 µg/mL, constituting a non-toxic substance. Given the above, it is understood that the antioxidant activity is closely related to the concentration of phenolics in the sample. Following this line of thought, the absence of antimicrobial activity is attributed to the absence of active metabolites responsible for this action. Therefore, knowing that plant extracts exhibit wide biological activity and that usually their action is related to the presence of certain constituents and consequently concentration, it is suggested the development of studies for the identification and quantification of active compounds present in this species besides studies of dose response and mechanisms of action for the purpose of specific data.