Biological effects of monomeric phenolic compounds from wine lees
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2020-07-22
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Nos últimos anos, os subprodutos do vinho têm sido considerados possíveis fontes de compostos fenólicos, uma vez que estes compostos, presentes na uva, são apenas parcialmente transferidos para o vinho, julgando-se que a maioria dos compostos fenólicos ainda permanece no resíduo, pois está presente nas partes sólidas da uva. Assim, a recuperação de fenóis a partir de resíduos industriais está a ganhar considerável atenção, principalmente devido à atividade antioxidante e à eliminação de radicais livres. As borras de vinho são os resíduos gerados durante os processos de fermentação e envelhecimento de diferentes atividades industriais relacionadas com a indústria vinícola. A extração de polifenóis valiosos a partir de subprodutos pode reduzir o impacto ambiental de algumas dessas substâncias nos campos cultivados e na água de irrigação e, por outro lado, podem constituir uma fonte valiosa de fenólicos naturais para várias indústrias, nomeadamente a farmacêutica e alimentar. Tendo isto em consideração, esta investigação teve como objetivo contribuir para a caracterização da fração fenólica de borras de vinho obtidas da casta Vitis vinífera, perceber o efeito de diferentes solventes (etanol e de metanol/água), sua concentração, e o efeito da liofilização do extrato de borras na eficiência de extração da fração fenólica. Por fim, pretendeu-se ainda avaliar a atividade antioxidante, antimicrobiana e genotóxica dos extratos de borras obtidos. Os resultados mostraram que a liofilização dos extratos resultantes da extração com etanol (extratos etanólicos) não afeta a composição química destes. O etanol provou ser o solvente mais adequado para a extração fenólica, uma vez que os extratos etanólicos apresentaram maior teor fenólico do que os extratos resultantes da extração com metanol (extratos metanólicos), à exceção da malvidin-3-O-glucósido em que os resultados provaram que o solvente mais eficaz para extrair malvidina era o metanol a 70% (v/v). A concentração do solvente, no caso dos extratos metanólicos teve um efeito significativo na composição fenólica dos extratos, pois aqueles extraídos com maior concentração de metanol (70%, v/v) apresentaram maior quantidade fenólica do que aqueles que resultaram da extração com menor concentração de metanol (50%, v/v). Relativamente aos resultados obtidos, as amostras extraídas com 70% (v/v) de metanol revelaram possuir 20% mais concentração de fenóis totais do que as amostras extraídas com menor concentração de metanol (50%, v/v), verificou-se também um aumento de 23% no teor em orto-difenóis, cerca de 22% no teor em flavonóides e ainda um aumento do teor de malvidina-3-O-glucósido de cerca de 46%. No que se refere à bioactividade dos extratos, avaliou-se a atividade antioxidante, antimicrobiana e genotóxica. A atividade antioxidante revelou que a liofilização dos extratos pode ser dispensada uma vez que não causou alterações significativas entre os extratos etanólicos frescos e liofilizados, ao contrário dos extratos extraídos com metanol onde a maior concentração de metanol (70%, v/v) mostrou uma capacidade antioxidante 20% mais elevada que as amostras extraídas com menor concentração de metanol (50%, v/v) no método do ABTS (2,2'-azino-bis(3-ethilbenzotiazolina-6-áido sulfónico)) e cerca de 38% mais elevada no método do DPPH (2,2-difenil-1-picril-hidrazil). Comparando os dois métodos (ABTS e DPPH), os extratos etanólicos apresentaram um poder antioxidante cerca de três vezes maior que os extratos metanólicos no método do ABTS enquanto que os extratos metanólicos mostraram uma atividade antioxidante quatro vezes mais potente que os extratos etanólicos no método do DPPH. Em relação à atividade antimicrobiana, nenhuma das diferentes concentrações testadas (10, 100, 500, 1000 mg/L equivalente de ácido gálico (GAE)) revelou halos de inibição significativos, embora as bactérias gram-positivas Staphylococcus aureus e Enterococcus faecalis tivessem apresentado alguma suscetibilidade aos extratos, embora pouco significativa. O efeito genotóxico dos extratos de borras de vinho, em termos de dano no DNA, foi testado em linfócitos, tendo-se verificado efeito genotóxico e ausência de capacidade protetora contra o dano oxidativo provocado por peróxido de hidrogénio através do ensaio cometa.
In recent years, wine by-products have been considered possible sources of phenolic compounds, since these compounds, present in the grape, are only partially transferred to the wine, considering that most of the phenolic compounds still remain in the residue, because it is present in the solid parts of the grape. Thus, the recovery of phenols from industrial waste is gaining considerable attention, mainly due to the radical scavenging activity. Wine lees are the residues generated during the fermentation and aging processes of different industrial activities related to the wine industry. The extraction of valuable polyphenols from by-products can reduce the environmental impact of some of these substances in cultivated fields and in irrigation water and, on the other hand, can constitute a valuable source of natural phenolics for various industries, namely pharmaceutical and food. Taking this in consideration, this research aimed to contribute to the characterization of the phenolic fraction of wine lees obtained from the species Vitis vinifera, to understand the effect of different solvents (aqueous ethanol and methanol solutions), their concentration, and the effect of the lyophilization of the extract of lees in the extraction efficiency of the phenolic fraction. Finally, it was also intended to evaluate the antioxidant, antimicrobial and genotoxic activity of the obtained lees extracts. The results showed that the lyophilization of extracts resulting from extraction with ethanol (ethanolic extracts) does not affect their chemical composition. Ethanol proved to be the most suitable solvent for phenolic extraction, since ethanolic extracts had a higher phenolic content than extracts resulting from extraction with methanol (methanolic extracts), with the exception of malvidin-3-O-glucoside in which results proved that the most effective solvent for extracting malvidin was 70% (v/v) the methanol. The concentration of the solvent, in the case of methanolic extracts, had a significant effect on the phenolic composition of the extracts, since those extracted with a higher concentration of methanol (70%, v/v) had a higher phenolic amount than those that resulted from the extraction with lower concentration of methanol (50%, v/v). Regarding the results obtained, the samples extracted with 70% (v/v) of methanol revealed to have 20% more concentration of total phenols than the samples extracted with lower concentration of methanol (50%, v/v). It was also verified an increase of 23% in the content of ortho-diphenols, about 22% in the content of flavonoids and an increase in the content of malvidin-3-O-glucoside of about 46%. Regarding the bioactivity of the extracts, the antioxidant, antimicrobial and genotoxic activity was evaluated. The antioxidant activity revealed that the lyophilization of the extracts can be dispensed with since it did not cause significant changes between the fresh and lyophilized ethanol extracts, unlike the extracts obtained by extraction with methanol where the highest concentration of methanol (70%, v/v) showed an antioxidant capacity 20% higher than samples extracted with lower concentration of methanol (50%, v/v) in the ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) method and about 38% higher in the DPPH (2,2-diphenyl-1-picrylhydrazyl) method. Comparing the two methods (ABTS and DPPH), the ethanolic extracts showed an antioxidant power about three times greater than the methanolic extracts when evaluated by the ABTS method while the methanolic extracts showed an antioxidant activity four times more potent than the ethanolic extracts in the DPPH method. Regarding antimicrobial activity, none of the different concentrations tested (10, 100, 500, 1000 mg/L equivalent of gallic acid (GAE)) revealed significant inhibition halos, although gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis revealed some susceptibility to the extracts, although not significant. The genotoxic effect of wine lees extracts, in terms of DNA damage, was tested in lymphocytes, with a genotoxic effect and lack of protective capacity against oxidative damage caused by hydrogen peroxide through single cell gel eletrophoresis assay.
In recent years, wine by-products have been considered possible sources of phenolic compounds, since these compounds, present in the grape, are only partially transferred to the wine, considering that most of the phenolic compounds still remain in the residue, because it is present in the solid parts of the grape. Thus, the recovery of phenols from industrial waste is gaining considerable attention, mainly due to the radical scavenging activity. Wine lees are the residues generated during the fermentation and aging processes of different industrial activities related to the wine industry. The extraction of valuable polyphenols from by-products can reduce the environmental impact of some of these substances in cultivated fields and in irrigation water and, on the other hand, can constitute a valuable source of natural phenolics for various industries, namely pharmaceutical and food. Taking this in consideration, this research aimed to contribute to the characterization of the phenolic fraction of wine lees obtained from the species Vitis vinifera, to understand the effect of different solvents (aqueous ethanol and methanol solutions), their concentration, and the effect of the lyophilization of the extract of lees in the extraction efficiency of the phenolic fraction. Finally, it was also intended to evaluate the antioxidant, antimicrobial and genotoxic activity of the obtained lees extracts. The results showed that the lyophilization of extracts resulting from extraction with ethanol (ethanolic extracts) does not affect their chemical composition. Ethanol proved to be the most suitable solvent for phenolic extraction, since ethanolic extracts had a higher phenolic content than extracts resulting from extraction with methanol (methanolic extracts), with the exception of malvidin-3-O-glucoside in which results proved that the most effective solvent for extracting malvidin was 70% (v/v) the methanol. The concentration of the solvent, in the case of methanolic extracts, had a significant effect on the phenolic composition of the extracts, since those extracted with a higher concentration of methanol (70%, v/v) had a higher phenolic amount than those that resulted from the extraction with lower concentration of methanol (50%, v/v). Regarding the results obtained, the samples extracted with 70% (v/v) of methanol revealed to have 20% more concentration of total phenols than the samples extracted with lower concentration of methanol (50%, v/v). It was also verified an increase of 23% in the content of ortho-diphenols, about 22% in the content of flavonoids and an increase in the content of malvidin-3-O-glucoside of about 46%. Regarding the bioactivity of the extracts, the antioxidant, antimicrobial and genotoxic activity was evaluated. The antioxidant activity revealed that the lyophilization of the extracts can be dispensed with since it did not cause significant changes between the fresh and lyophilized ethanol extracts, unlike the extracts obtained by extraction with methanol where the highest concentration of methanol (70%, v/v) showed an antioxidant capacity 20% higher than samples extracted with lower concentration of methanol (50%, v/v) in the ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) method and about 38% higher in the DPPH (2,2-diphenyl-1-picrylhydrazyl) method. Comparing the two methods (ABTS and DPPH), the ethanolic extracts showed an antioxidant power about three times greater than the methanolic extracts when evaluated by the ABTS method while the methanolic extracts showed an antioxidant activity four times more potent than the ethanolic extracts in the DPPH method. Regarding antimicrobial activity, none of the different concentrations tested (10, 100, 500, 1000 mg/L equivalent of gallic acid (GAE)) revealed significant inhibition halos, although gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis revealed some susceptibility to the extracts, although not significant. The genotoxic effect of wine lees extracts, in terms of DNA damage, was tested in lymphocytes, with a genotoxic effect and lack of protective capacity against oxidative damage caused by hydrogen peroxide through single cell gel eletrophoresis assay.
Descrição
This work was prepared as an original dissertation aiming to obtain the degree of Master´s degree in Biochemistry
Palavras-chave
borras de vinho , compostos fenólicos