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Abstract(s)
A lenhina é o segundo polímero natural mais abundante depois da celulose. Este constituinte das plantas é um componente subutilizado da biomassa vegetal renovável. A lenhina é um polímero multifuncional sintetizado por todas as plantas vasculares por acoplamento radical de grupos fenilhidroxipropanóides, rica em resíduos polifenólicos, possuindo potencial para ser usada como fonte natural de antioxidantes. Os resíduos da agricultura, como as podas dos pomares, sendo ricos em lenhina, representam uma importante matéria-prima para obtenção de antioxidantes. Assim, de modo a desenvolver um produto de valor acrescentado, os resíduos da poda de cerejeiras Prunus avium var. Burlat foram moídos e crivados para se obter um tamanho de partícula adequado. A amostra original foi analisada em termos da sua composição química geral e usando métodos diferentes de extração obtiveram-se várias amostras de lenhina. Estas foram analisadas em termos de rendimento de extração e caraterizadas espectroscopicamente por FTIR e RMN de 1H e 13C. As amostras mais promissoras foram analisadas quanto ao teor em fenóis totais e atividade antioxidante por diferentes técnicas. Para completar este trabalho foram efetuados estudos de viabilidade celular em linhas celulares de fibroblastos (NHDF) pelo teste do MTT e por doseamento da proteína através do método do ácido bicinconínico.
Concluiu-se que o método de extração que apresentou maior rendimento foi o que usou ácido fórmico, assistida com micro-ondas, variando os rendimentos das extrações para os diferentes métodos entre 5 e 18%. As maiores concentrações de compostos fenólicos foram encontradas nas extrações ácidas (182,55 e 244,32 mg equivalentes de ácido gálico/ g de matéria seca (GAE/g)), enquanto que as extrações alcalinas apresentaram valores inferiores (130,0 e 68,19 mg GAE/g). As amostras apresentaram atividade antioxidante muito forte quando extraídas com processos ácidos e moderada quando extraídas com processos alcalinos. Os resultados da viabilidade celular foram positivos tendo em conta que, quando em concentrações mais elevadas, a lenhina não apresentou efeitos citotóxicos nem aumentou a proliferação celular, reduzindo assim a probabilidade de ocorrência de mutações, sendo este facto explicado pela ausência de morte celular.
Lignin is the most abundant natural polymer after cellulose. This plant constituent is an underutilized component of renewable plant biomass. Lignin is a multifunctional polymer synthesized by all vascular plants by radical coupling of phenylhydroxypropanoid groups, rich in polyphenolic residues, having the potential to be used as a natural source of antioxidants. Agricultural residues, such as pruning of orchards, being rich in lignin, represent an important raw material for obtaining antioxidants. Thus, in order to develop a value-added product, residues of cherry pruning Prunus avium var. Burlat were milled and screened to obtain a suitable particle size. The original sample was analyzed in terms of general chemical composition and several lignin samples were obtained using different extraction methods. These were analyzed in terms of extraction yield and spectroscopically characterized by FTIR and 1H- and 13C-NMR. The most promising samples were analyzed for total phenol content and antioxidant activity using several techniques. To complete this work, cell viability studies were made with fibroblasts cell lines (NHDF) using the MTT test and protein dosing via the bicinchoninic acid method. It was concluded that the extraction method with the highest yield was the one using formic acid, assisted by microwave, with yields varying between 5 and 18%. The highest amounts of phenolic compounds were obtained by acidic extractions (182,55 e 244,32 mg of acid gallic equivalent per g of dry matter, (mgGAE/g)), while alkaline extractions exhibited the lowest values (130,5 and 244,32 mg GAE/g). Lignin samples presented very strong antioxidant activity when extracted by acid processes and moderated when extracted by alkaline processes. The results of cell viability were positive considering that at higher concentrations, lignin did not present cytotoxic effects nor increased cell proliferation, thus reducing the probability of occurrence of mutations, which is explained by the absence of cell death.
Lignin is the most abundant natural polymer after cellulose. This plant constituent is an underutilized component of renewable plant biomass. Lignin is a multifunctional polymer synthesized by all vascular plants by radical coupling of phenylhydroxypropanoid groups, rich in polyphenolic residues, having the potential to be used as a natural source of antioxidants. Agricultural residues, such as pruning of orchards, being rich in lignin, represent an important raw material for obtaining antioxidants. Thus, in order to develop a value-added product, residues of cherry pruning Prunus avium var. Burlat were milled and screened to obtain a suitable particle size. The original sample was analyzed in terms of general chemical composition and several lignin samples were obtained using different extraction methods. These were analyzed in terms of extraction yield and spectroscopically characterized by FTIR and 1H- and 13C-NMR. The most promising samples were analyzed for total phenol content and antioxidant activity using several techniques. To complete this work, cell viability studies were made with fibroblasts cell lines (NHDF) using the MTT test and protein dosing via the bicinchoninic acid method. It was concluded that the extraction method with the highest yield was the one using formic acid, assisted by microwave, with yields varying between 5 and 18%. The highest amounts of phenolic compounds were obtained by acidic extractions (182,55 e 244,32 mg of acid gallic equivalent per g of dry matter, (mgGAE/g)), while alkaline extractions exhibited the lowest values (130,5 and 244,32 mg GAE/g). Lignin samples presented very strong antioxidant activity when extracted by acid processes and moderated when extracted by alkaline processes. The results of cell viability were positive considering that at higher concentrations, lignin did not present cytotoxic effects nor increased cell proliferation, thus reducing the probability of occurrence of mutations, which is explained by the absence of cell death.
Description
Keywords
Atividade Antioxidante Ensaios de Citotoxicidade. Fenóis Totais Lenhina Métodos de Extração Prunus Avium Var. Burlat