Effects of Different Oligochitosans on Isoflavone Metabolites, Antioxidant Activity, and Isoflavone Biosynthetic Genes in Soybean (Glycine max) Seeds during Germination

Resumo

Cinco oligoquitosanos com graus crescentes de polimerização (DPs), ou seja, de quitotriose a quitoheptaose, foram examinados para esclarecer a relação estrutura-bioatividade entre os DPs de oligoquitosanos e seus efeitos nos metabólitos de isoflavonas, teores fenólicos e flavonoides totais (TPC e TFC, respectivamente) e atividade antioxidante da soja ( Glycine max) sementes durante a germinação. Oligoquitosanos de diferentes DPs exibiram influências variadas no TPC, TFC e atividades antioxidantes de sementes de soja. A quitohexaose exerceu um forte efeito e aumentou significativamente os parâmetros acima mencionados em sementes de soja 72 h após a germinação. Genistina, malonilgenistina e genisteína foram as principais isoflavonas encontradas, e os conteúdos de genistina e genisteína aumentaram significativamente em 67,32% e 131,38%, respectivamente, após o tratamento com quitohexaose. Vários genes críticos envolvidos na biossíntese de isoflavonas (ou seja, PAL , CHS , CHI , IFS) de soja tratada com e sem quitohexaose foram analisados, e os resultados sugeriram que a aplicação de quitohexaose poderia estimular dramaticamente a transcrição desses genes.

Abstract

Five oligochitosans with increasing degrees of polymerization (DPs), i.e., from chitotriose to chitoheptaose, were examined to clarify the structure–bioactivity relationship between the DPs of oligochitosans and their effects on the isoflavone metabolites, total phenolic and flavonoid contents (TPC and TFC, respectively), and antioxidant activity of soybean (Glycine max) seeds during germination. Oligochitosans of different DPs exhibited varying influences on the TPC, TFC, and antioxidant activities of soybean seeds. Chitohexaose exerted a strong effect and significantly increased the aforementioned parameters in soybean seeds 72 h after germination. Genistin, malonylgenistin, and genistein were the main isoflavones found, and the genistin and genistein contents were significantly enhanced by 67.32% and 131.38%, respectively, after chitohexaose treatment. Several critical genes involved in the isoflavone biosynthesis (i.e., PAL, CHS, CHI, IFS) of soybeans treated with and without chitohexaose were analyzed, and results suggested that chitohexaose application could dramatically stimulate the transcription of these genes.