Isolamento, identificação, atividade antioxidante e variabilidade temporal de compostos fenólicos de folhas de Eucalyptus microcorys F. Muell

• Ano de defesa: 2016
• Autor(a) principal: Fortes , Gilmara Aparecida Corrêa
• Orientador(a): Santos , Suzana da Costa
• Banca de defesa: Santos , Suzana da Costa, Costa , Maísa Borges, Moraes , Moemy Gomes de, Leandro , Wilson Mozena, Queiros Júnior , Luiz Henrique Keng
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Goiás
• Programa de Pós-Graduação: Programa de Pós-graduação em Química (IQ)
• Departamento: Instituto de Química - IQ (RG)
• País: Brasil
• Palavras-chave em Português: Eucalyptus microcorys; Compostos fenólicos; Elagitaninos; Atividade antioxidante; Curva de resposta principal
• Palavras-chave em Inglês: Eucalyptus microcorys; Phenolic compounds; Ellagitannins; Antioxidant activity; Principal response curves
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: http://repositorio.bc.ufg.br/tede/handle/tede/6347

The species Eucalyptus microcorys has important medicinal potential, since its leaves are rich in 1,8-cineole and hydrolysable tannins. The isolation of phenolic compounds from the leaves of this species was carried out using chromatographic methods and structural elucidation of the compounds was made by spectroscopic analysis, such as UV, IR, MS and 1H NMR and 13C, 1D and 2-D experiments. Seventeen compounds were isolated and identified, among them seven ellagitannins, four galloyl esters, four phenolic acids and two flavonoids. The acylated glycoside, 4-O-(4’,6’-di-O-galloyl -D-glucopyranosyl)-trans-p-coumaric acid, named microcoryn was first isolated in this work. Antioxidant activity of the isolated compounds was determined by two in vitro methods, free radical scavenging (DPPH) and the oxygen radical absorption capacity (ORAC). The results indicated that compounds with more phenolic hydroxyls exhibited the highest antioxidant activity, and the macrocyclic dimer oenothein B, major compound of this species, showed the highest activity. Seasonal factors and plant nutrient levels can influence the biosynthesis of secondary metabolites. This study also evaluated the temporal variability of phenolic compounds based on foliar nutrients and climatic changes in the period of two years with quarterly collections. The data were subjected to analysis of variance (ANOVA two-way); where the concentrations of oenothein B and total phenols did not show significant variations within each year, only between different years, while total tannin (astringency) varied only within the first year. Data were also analyzed by the multivariate statistical technique of time series, called primary response curve (PRC). This analysis showed that the variables that contributed most to the difference between the two years of study were copper, potassium, phosphorus, iron and magnesium as foliar nutrients, moisture and precipitation as climatic factors. Joining the results of two analyzes may suggest that variations in oenothein B levels and total phenols were influenced inversely by nutrients magnesium and iron, and directly by copper and potassium. The humidity can be an important climatic factor to the changes in total tannins, between months and years, while rainfall cannot be considered a determining factor in the variation of phenolic compounds, as it showed conflicting trends.