PERFIL QUÍMICO E AÇÃO DEFENSIVA COMPARATIVA DE EXTRATOS BRUTOS DE DIFERENTES LOCALIDADES DO LITORAL BRASILEIRO DA ALGA PARDA MARINHA Dictyota mertensii (DICTYOTALES, PHAEOPHYTA)

• Ano de defesa: 2006
• Autor(a) principal: Freitas, Odinéia do Socorro Pamplona
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Programa de Pós-graduação em Química Orgânica; Química Orgânica
• Palavras-chave em Português: diterpenos; herbivoría do litoral brasileiro; Lytechinus variegatus; Diterpenes; Brazilian littoral herbivory; Dictyota mertensii; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA
• Link de acesso: https://app.uff.br/riuff/handle/1/20967

Several types and concentrations of secondary metabolites can characterize the broad and diversified chemical profile of the seaweeds. This variability can be due to intrinsic aspects (genetics) or extrinsic (environmental factors), but unexplored yet. In the present study were analyzed the crude extracts of specimens of five populations of D. mertensii collected in several sites in Brazilian littoral to evaluate the quali- and quantitative production of its diterpenes and its defensive action against herbivory. The specimens of D. mertensii were collected in populations of this seaweed species inhabiting Atol das Rocas (RN), Riacho Doce (AL), Itapuã (BA), Praia Preta (RJ) and Praia Rasa (RJ). The analysis of the extracts were carried out by Thin Layer Cromatography (TLC), Nuclear Magnetic Ressonace (1H NMR) and Gas Chromatography coupled to Mass Spectrometer (GC/MS). The populations of D. mertensii were characterized by the presence of prenylated guaiane diterpenes and fucosterol. Among the diterpenes, there was a quantitative variation in its major compounds, such as pachydictyol A, isopachydictyol A, o dictyol B and its corresponding acetate, dictyol C, dictyoxide and dictyol H, but expressing a clear taxonomic pattern. The analysis by GC/MS and NMR revealed the a comparison between the populations of D. mertensii, and the establishment of a variable chemical profile of this species. The characterization of its diterpenes was efficient to establish the chemical similarity between the Praia do Riacho Doce (AL), Praia de Itapuã (BA) and Praia Preta (RJ) populations. Biological assays using artifical foods and lipophylic fractions (containing mainly diterpenes, sterols e fat acids), were used to evaluate the efficiency of these chemicals as defense against the herbivory by the sea-urchin Lytechinus variegatus. Under ecological view, this study verified the defensive action of lipophylic fractions to five studied populations of D. mertensii covering for the first time a broad latitudinal range in Brazilian coast from Rio Grande do Norte State to south of Rio de Janeiro. The variation in metabolites production was expressed in the biological assays, indicating that population from Alagoas was better defended agianst herbivory. Probably the variability of secondary metabolites production in D. mertensii populations is not only due to herbivory pressure, but to chemical characteristics of this species or other local environmental conditions. These results broader the information about the function or the ecological significance of these secondary metabolites in the Brazilian littoral.