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Advisor(s)
Abstract(s)
A extração de compostos fenólicos é, tradicionalmente, realizada utilizando solventes orgânicos voláteis que apresentam diversas desvantagens entre as quais toxicidade, volatilidade e inflamabilidade. Neste trabalho pretende-se estudar a utilização de solventes alternativos que possam colmatar algumas das desvantagens descritas, mantendo ou superando o desempenho dos solventes convencionais. Assim, numa primeira fase foram estudadas soluções aquosas de quatro compostos iónicos (cloreto de 1-butil-3-metilimidazólio, cloreto de tetrametilamónio, cloreto de cetilpiridínio, brometo de miristiltrimetilamónio) e, posteriormente, dois surfactantes não iónicos (Triton X-100 e Genapol X-080) e um surfactante aniónico (dodecil sulfato de sódio). Além do tipo de solvente, avaliou-se ainda o efeito da concentração e do tempo de contacto na eficiência da extração.
Como planta modelo, escolheu-se a espécie Asparagus acutifolius L., uma planta comestível, fonte de compostos bioativos, mas apresentando um perfil fenólico simples dominado por apenas 3 compostos.
Os resultados obtidos indicaram que, à temperatura ambiente, o solvente ótimo foi uma solução aquosa de cloreto de cetilpiridínio (CPyrCl), com concentração 0,1 M, durante 1 hora de tempo de extração que, comparando com o solvente convencional (metanol: água, 80:20%, v/v), resulta numa eficiência significativamente maior na extração dos compostos fenólicos encontrados em A. acutifolius. Verificou-se, no entanto, que nas condições de máxima eficiência de extração, o extrato de CPyrCl revelou menor atividade antioxidante comparativamente com o resultado da extração hidrometanólica, provavelmente devido a interferências da utilização deste tipo de solventes nos métodos in vitro utilizados na avaliação da capacidade antioxidante, aspeto que necessita de elucidação em estudos posteriores.
The extraction of phenolic compounds is traditionally carried out using volatile organic solvents which have several disadvantages including toxicity, volatility and flammability. In this work it is intended to study the use of alternative solvents that can overcome some of the disadvantages described, maintaining or exceeding the performance of conventional solvents. Thus, in a first stage, aqueous solutions of four ionic compounds (1-butyl-3-methylimidazolium chloride, tetramethylammonium chloride, cetylpyridinium chloride, myristyltrimethylammonium bromide) were studied and, subsequently, two non-ionic surfactants (Triton X-100 and Genapol X-080) and an anionic surfactant (sodium dodecyl sulfate) were also considered. In addition to the type of solvent, the effect of concentration and contact time on the extraction efficiency was also assessed. The edible species Asparagus acutifolius L., a source of bioactive compounds, with a simple phenolic profile with only 3 compounds, was chosen as plant model. The results showed that at room temperature, the optimum solvent was an aqueous solution of cetylpyridinium chloride (CPyrCl) with concentration 0.1 M, and extraction time of 1 hour that, when compared to the conventional method (methanol/water 80:20%, v/v), presents a significantly higher efficiency for the extraction of the phenolic compounds present in A. acutifolius. It was found, however, that in conditions of maximum efficiency of extraction, the CPryCl extract showed lower antioxidant activity compared to the result of hydromethanolic extraction, probably due to interferences from the use of such solvents in the in vitro methods used to evaluate the antioxidant capacity, aspect which requires further elucidation studies.
The extraction of phenolic compounds is traditionally carried out using volatile organic solvents which have several disadvantages including toxicity, volatility and flammability. In this work it is intended to study the use of alternative solvents that can overcome some of the disadvantages described, maintaining or exceeding the performance of conventional solvents. Thus, in a first stage, aqueous solutions of four ionic compounds (1-butyl-3-methylimidazolium chloride, tetramethylammonium chloride, cetylpyridinium chloride, myristyltrimethylammonium bromide) were studied and, subsequently, two non-ionic surfactants (Triton X-100 and Genapol X-080) and an anionic surfactant (sodium dodecyl sulfate) were also considered. In addition to the type of solvent, the effect of concentration and contact time on the extraction efficiency was also assessed. The edible species Asparagus acutifolius L., a source of bioactive compounds, with a simple phenolic profile with only 3 compounds, was chosen as plant model. The results showed that at room temperature, the optimum solvent was an aqueous solution of cetylpyridinium chloride (CPyrCl) with concentration 0.1 M, and extraction time of 1 hour that, when compared to the conventional method (methanol/water 80:20%, v/v), presents a significantly higher efficiency for the extraction of the phenolic compounds present in A. acutifolius. It was found, however, that in conditions of maximum efficiency of extraction, the CPryCl extract showed lower antioxidant activity compared to the result of hydromethanolic extraction, probably due to interferences from the use of such solvents in the in vitro methods used to evaluate the antioxidant capacity, aspect which requires further elucidation studies.
Description
Keywords
Compostos fenólicos Líquidos iónicos Surfactantes