Metabólitos secundários de algas pardas: Implicações ecológicas, taxonômicas e filogenéticas

Abstract

Brown algae (Phaeophyta) are the group with he largest biomass in the Brazilian coast Representative specimens of the Fucales and Dictyotales orders were studied in this work are among the most evolved of brown algae. Our photochemical results indicate a balance in the production of tannins, terpenes and sterols. Fucales algae, which are rich in sterols, show small amounts or absence of terpenes, while with Dictyotales, the inverse occurs. Surprisingly, tannins were found in small concentrations, contrary to what is observed in temperate regions. Herbivory tests were conducted, showing that the substances employed, the steroidal fraction and the diterpens dictyol H and 4 α-acetoxy-14α-hydroxydolastane-1(15),7,9-triene, isolated from Sargassum furcatum Kuetzing, Dictyota ceruicornis Kuetzing, Dictyota mertensii (Martius) Kuetzing, respectively, seem to be inactive towards grazing by the marine herbivore amphipod Parhyale hawaiensis Dana. Finally, a chemo-sistematic analysis of these two orders of brown algae was made, based of literature data and employing taxonomic índices such as "oxidaton index", and "skeleton evolutive advancement índex". Our results show that terpenes, either of simple or mixed biossynthetic origin, can be good taxonomic markers. Meroterpenes (mixed biossynthetic origin terpenes) are the most evolved of the chemo-systematic and phylogenetic markers so far studied for brown algae.