Dictyota mertensii: investigação química e farmacológica de seus extratos

Abstract

The marine natural products represent a huge potential for the discovery of new drugs. Among the marine organisms producers of bioactive compounds appear the macroalgae, with highlighting for the brown algae, which includes ca. 1800 species distributed in 285 genera. These are producers of structurally diversified secondary metabolites which exhibit several biological and pharmacological activities. The Dictyota genus is known as a prolific source of secondary metabolites, especially of diterpenes such as xenicanes, prenylated guaianes and dolabellanes. Some of these compounds exhibit antimicrobial, cytotoxic and antifungal activities, as well as can act in the defense mechanism. The seaweed Dictyota mertensii, collected on the beach of Flecheiras, Trairi-CE, was subjected to extraction in the solvents: hexane, ethyl acetate and ethanol. These extracts were chromatograped using classical chromatography techniques such as: chromatography on silica gel, exclusion chromatography using Sephadex® LH-20 and high performance liquid chromatography (HPLC). The structures of the isolated compounds were made by interpretation of spectroscopic and spectrometric techniques, such as: MS, 1H and 13C NMR, COSY, HMQC, HMBC and NOESY. The interpretation of the spectroscopic data, mainly of 1H and 13C NMR data led to structure elucidation of five compounds, being two quaternary amonium salts and three diterpenes, two of them with guaiane structure and one dolabellane. The compounds DM-01 to DM-04 were sumitted to cell viability and inhibition of nitric oxide production activities. As regards, the cell viability assays of the compounds with similar structure DM-01 and DM-02 (quaternary ammonium salts) showed similar cytotoxicity from the concentration of 12 μM, while the compounds DM-03 and DM-04 showed cytotoxicity over the concentration of 100 μM. In the inhibition NO assays, compound DM-02 showed a significant reduction in NO production from the concentration of 1.5 μM, while DM-01, 03 and 04 compounds showed reductive capacity from the concentration of 3 μM. The best reducing effect was observed at the concentrations of 50 μM of compounds DM-03 and DM-04.