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Master's Dissertation
DOI
10.11606/D.60.2011.tde-21092011-113131
Document
Author
Full name
Vanessa Silveira Fortes
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2011
Supervisor
Committee
Fonseca, Maria José Vieira (President)
Polizeli, Maria de Lourdes Teixeira de Moraes
Saltoratto, Ana Lucia Fachin
Title in Portuguese
Caracterização química e avaliação da atividade antioxidante e citotóxica do extrato da soja (Glycine max) biotransformada pelo fungo Aspergillus awamori
Keywords in Portuguese
antioxidante
Aspergillus awamori
biotransformação
citotoxicidade
glicosidase
isoflavonas agliconas
soja
Abstract in Portuguese
A soja (Glycine max) contém uma variedade de compostos com comprovada atividade biológica, tais como as isoflavonas, que estão presentes em diferentes formas, glicosiladas e agliconas. Além disso, a soja contém uma grande quantidade de proteínas, que são consideradas fontes de peptídeos bioativos. As isoflavonas agliconas, daidzeína e genisteína, possuem maior atividade antioxidante que as glicosiladas, daidzina e genistina. No entanto, os grãos de soja são ricos nas formas glicosiladas das isoflavonas. Estudos mostram que a biotransformação da soja, por micro-organismos e enzimas, leva ao aumento dos teores das isoflavonas agliconas, as quais são liberadas pela ação de enzimas -glicosidases, que clivam as ligações -glicosídicas das isoflavonas glicosiladas, e também pode possibilitar a hidrólise das proteínas da soja. Além disso, pesquisadores têm demonstrado aumento na atividade antioxidante e na prevenção e/ou supressão de certos cânceres após biotransformação da soja. Neste contexto, foi realizada a biotransformação da soja pelo fungo A. awamori, e por uma mistura enzimática, proveniente do processo fermentativo deste fungo na soja. Os extratos da soja biotransformada, não biotransformada, e o extrato comercial isoflavin beta®, rico em isoflavonas, foram avaliados quanto aos perfis cromatográficos, teores de daidzeína, genisteína, proteínas, aminoácidos e/ou peptídeos, potencial antioxidante e atividade citotóxica frente a células de fibroblasto e melanoma. O modo de morte celular das células de melanoma, necrose ou apoptose, também foi avaliado. A biotransformação da soja, pelos dois processos, resultou em extratos enriquecidos com isoflavonas agliconas e aminoácidos e/ou peptídeos, e com maior atividade antioxidante que o extrato da soja não biotransformada. Os dois processos de biotransformação da soja resultaram em extratos com características químicas e biológicas diferentes. O conteúdo de daidzeína, proteínas, aminoácidos e/ou peptídeos encontrados no extrato da soja biotransformada pelo fungo foram 6%, 56% e 357%, respectivamente, superiores ao extrato da soja biotransformada pela mistura enzimática. Ao contrário do observado para o teor de genisteína que foi 48% maior no extrato da soja biotransformada pela mistura enzimática. O extrato da soja biotransformada pelo fungo apresentou maior atividade antioxidante que o extrato da soja biotransformada pela mistura enzimática, além disso, foi o único dos extratos aqui estudados que apresentou citotoxicidade seletiva para as células de melanoma, induzindo morte celular por apoptose destas células cancerosas. Sendo assim, os resultados obtidos pelo extrato da soja biotransformada pelo fungo A. awamori fornecem boas perspectivas para futura utilização deste extrato como antitumoral.
Title in English
Chemical characterization and evaluation of the antioxidant and cytotoxic activity of the soybean (Glycine max) extract biotransformed by the Aspergillus awamori
Keywords in English
aglycone isoflavone
antioxidant
Aspergillus awamori
biotransformation
citotoxicity
glucosidase
soy bean
Abstract in English
Soybean (Glycine max) contains a variety of compounds with proven biological activity, such as isoflavones, which are present in different forms, glycosides and aglycones. In addition, soybean contains a lot of proteins, which are considered sources of bioactive peptides. The aglycone isoflavones, daidzein and genistein, have higher antioxidant activity than the glucoside ones, daidzin and genistin. However, soybean grains are rich in the glycosylated forms of isoflavones. Studies have shown that the soybean biotransformation, by microorganisms and enzymes, lead to increased levels of aglycone isoflavones, which are released by the action of -glycosidase enzymes, which cleave the -glycosidic bonds of isoflavone glucosides, and can also allow the hydrolysis of soybean proteins. Additionally, researchers have shown an increase in the antioxidant activity and in the prevention and/or suppression of certain cancers after soybean biotransformation. In this context, it was performed the biotransformation of soybeans with the fungus A. awamori, and with an enzyme mixture, from the fermentation process of the fungus in soybean. The biotransformed, the non biotransformed soybean extracts and the marketed isoflavin beta® extract rich in isoflavones, were evaluated regarding their chromatographic profiles, levels of daidzein, genistein, proteins, amino acids and/or peptides, the antioxidant potential and the cytotoxic activity against melanoma cells and fibroblasts. The mode of cell death of melanoma cells, necrosis or apoptosis, was also evaluated. The biotransformation of soybean by the two processes resulted in extracts enriched with aglycone isoflavones and aminoacids and/or peptides, and with antioxidant activity higher than the non biotransformed soybean extract. The two processes of soybean biotransformation resulted in extracts with different chemical and biological characteristics. The contents of daidzein, proteins, aminoacids and/or peptides found in soybean extract biotransformed by the fungus were 6%, 56% and 357%, respectively, higher than the soybeam extract biotransformed by the enzyme mixture. Contrary to what was observed with the genistein content that was 48% higher in the soybean extract biotransformed by the enzyme mixture. The soybean extract biotransformed by the fungus had a higher antioxidant activity than the soybean extract biotransformed by the enzyme mixture, moreover, it was the unique extract among the ones studied in this work that showed selective cytotoxicity to melanoma cells, inducing cell death by apoptosis of these cancer cells. Thus, the obtained results of the soybean extract biotransformed by the fungus A. awamori provide good prospects for future use of this extract as antitumoral.
 
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Publishing Date
2011-11-17
 
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