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Abstract(s)
Desde a antiguidade, que as plantas desempenham um papel fundamental na medicina, sendo a base dos tratamentos tradicionais. Assim, grande parte do conhecimento atual sobre elas deve-se à medicina tradicional. Tendo em conta a sua importância, surgiu a necessidade de se realizarem estudos cada vez mais aprofundados destas, de forma a isolar-se os seus constituintes e as suas potenciais atividades biológicas.
Neste estudo foram investigados dois extratos provenientes de cascas de Salix salviifolia subsp. salviifolia, também conhecida como salgueiro branco, obtidos por extração com n-hexano e com etanol/água (80/20). Essencialmente, o objetivo foi fracionar e caraterizar quimicamente estes extratos e avaliar a sua atividade biológica por determinação da sua atividade antioxidante.
O estudo foi iniciado com o extrato de etanol/água, tendo-se realizado diversos fracionamentos que se demonstraram ineficazes, o que levou à adoção da estratégia dos grupos protetores. A estratégia mais eficaz acabou por ser a acetilação do extrato bruto, onde foi possível a identificação estrutural, por RMN (Ressonância Magnética Nuclear), de três produtos: 3-Acetil-3-hidroxi-6-metil-piran-2,4-diona; 3-Acetil-3,6-dimetil-piran-2,4-diona; Ácido (E)-2-acetil-3-hidroxibut-2-enóico. Por análise do extrato acetilado, no GC-MS (cromatografia gasosa acoplada a espetrometria de massa), foram identificados monossacáridos e dissacáridos acetilados e alguns glicósidos. Minoritariamente, também foram identificados esteroides, lactonas, furanocumarinas e salicoilsalicina. Este extrato demonstrou possuir um elevado conteúdo de fenóis totais e um teor relativamente baixo de flavonoides.
O extrato de n-hexano sofreu um processo de separação, o qual originou três fases, que foram estudadas separadamente e analisadas por GC-MS. Esta análise permitiu identificar alguns compostos nele presentes, concluindo-se que os terpenoides são os compostos maioritários. Para além destes, também foram identificados hidrocarbonetos e ácidos gordos esterificados com um grupo metilo.
Quanto à avaliação da atividade biológica, a sua determinação foi efetuada pelo método de DPPH (2,2-difenil-1-picrilhidrazil) e pelo sistema ß-caroteno/ácido linoleico. Esta avaliação apenas foi realizada para o extrato de etanol/água. O extrato demonstrou uma atividade antioxidante muito forte, pelo método de DPPH. Pelo sistema ß-caroteno/ácido linoleico, o extrato apresentou um poder antioxidante menor.
Since antiquity, plants have played a key role in medicine, being the basis of traditional treatments. Thus, almost all the current knowledge about them is due to traditional medicine. Once they are important, there was a need to develop more depth studies, to isolate their constituents and their potential biological activities. Therefore, in this study were analysed two extracts from barks from Salix salviifolia subsp. salviifolia, also known as white willow, obtained by extraction with n-hexane and with ethanol/water (80/20). Essentially, the objective was to fractionate and chemically characterize these extracts and evaluate their biological activity by determining their antioxidant activity. This study was started with the ethanol/water extract, in which were performed several fractionations, which proved to be ineffective. To solve this problem was adopted a strategy, which consisted in the use of the protective groups. The most effective strategy turned out to be the acetylation of the crude extract, where it was possible to identify three structural products by NMR (Nuclear Magnetic Resonance): 3-Acetyl-3-hydroxy-6-methyl-pyran-2,4-dione; 3-Acetyl-3,6-dimethyl-pyran-2,4-dione; (E)-2-Acetyl-3-hydroxybut-2-enoic acid. By the analysis of the acetylated extract, by GC-MS (Gas Chromatography-Mass Spectrometry), were identified several acetylated monosaccharides and disaccharides and some glycosides. In minority quantity have also been identified some steroids, lactones, furanocoumarins and salicoylsalicin. This extract has been shown to have a high content of total phenols and a relatively low content of flavonoids. The n-hexane extract underwent a separation process, which gave rise to three phases, which were studied separately and analysed by GC-MS. This analysis allowed to identify some compounds present in the extract, concluding that the terpenoids are the major compounds. In addition to these, hydrocarbons and methyl esters of fatty acids have also been identified. As for the biological activity evaluation, it was determinate by the DPPH (2,2-diphenyl-1-picrylhydrazyl) method and the ß-carotene/linoleic acid system. This evaluation was only performed for the ethanol/water extract. By the DPPH method, this extract showed a very strong antioxidant activity and by the ß-carotene/linoleic acid system, the extract had a lower antioxidant power.
Since antiquity, plants have played a key role in medicine, being the basis of traditional treatments. Thus, almost all the current knowledge about them is due to traditional medicine. Once they are important, there was a need to develop more depth studies, to isolate their constituents and their potential biological activities. Therefore, in this study were analysed two extracts from barks from Salix salviifolia subsp. salviifolia, also known as white willow, obtained by extraction with n-hexane and with ethanol/water (80/20). Essentially, the objective was to fractionate and chemically characterize these extracts and evaluate their biological activity by determining their antioxidant activity. This study was started with the ethanol/water extract, in which were performed several fractionations, which proved to be ineffective. To solve this problem was adopted a strategy, which consisted in the use of the protective groups. The most effective strategy turned out to be the acetylation of the crude extract, where it was possible to identify three structural products by NMR (Nuclear Magnetic Resonance): 3-Acetyl-3-hydroxy-6-methyl-pyran-2,4-dione; 3-Acetyl-3,6-dimethyl-pyran-2,4-dione; (E)-2-Acetyl-3-hydroxybut-2-enoic acid. By the analysis of the acetylated extract, by GC-MS (Gas Chromatography-Mass Spectrometry), were identified several acetylated monosaccharides and disaccharides and some glycosides. In minority quantity have also been identified some steroids, lactones, furanocoumarins and salicoylsalicin. This extract has been shown to have a high content of total phenols and a relatively low content of flavonoids. The n-hexane extract underwent a separation process, which gave rise to three phases, which were studied separately and analysed by GC-MS. This analysis allowed to identify some compounds present in the extract, concluding that the terpenoids are the major compounds. In addition to these, hydrocarbons and methyl esters of fatty acids have also been identified. As for the biological activity evaluation, it was determinate by the DPPH (2,2-diphenyl-1-picrylhydrazyl) method and the ß-carotene/linoleic acid system. This evaluation was only performed for the ethanol/water extract. By the DPPH method, this extract showed a very strong antioxidant activity and by the ß-carotene/linoleic acid system, the extract had a lower antioxidant power.
Description
Keywords
Atividade Antioxidante Caraterização Fitoquímica Extrato Etanol/Água Extrato N-Hexano Salix Salviifolia Subsp. Salviifolia