The polyphenols profile of co-fermented quinoa and black barley with Lactobacillus kisonensis and its in vitro bioactivities

Fermentation is a commonly used technique that can effectively enrich bioactive compounds, and further enhance the bioactivity of food. To effectively enrich polyphenols and flavonoids, the quinoa and black barley were co-fermented with Lactobacillus kisonensis in present study. The in vitro antioxidant bioactivities and inhibition rate on key enzymes related with glucose metabolism of the co-fermented cereals were evaluated; the secondary metabolites such as polyphenol and flavonoid were identified by UPLC-Q-TOF-MS E -untargeted metabolomics technique, and the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways were primarily analyzed. The results showed that the content of protein in the precipitate, as well as soluble and total dietary fiber, significantly increased ( p  < 0.05) in the co-fermented quinoa with black barley compared to the fermentation of quinoa or black barley alone or to the un-fermentation groups. The total contents of polyphenol and flavonoid in the co-fermented grains were significantly increased by 55.65% and 25.90%, respectively, compared with the un-fermentation group ( p  < 0.05). Elevated levels of polyphenol flavonoids, such as coumaric acid, (2R,3R)-Taxifolin7- O -α- l -rhamnopyranosyl-(1→6)-β- d -glucopyranoside and ferulic acid sodium, contributed to the significant improvement in in vitro bioactivities, such as antioxidant capacity and inhibitory activity on α-amylase and α-glucosidase. Correlation analysis revealed positive associations between 9 polyphenols and flavonoids in the supernatant and 12 in the precipitate with these in vitro bioactivities mentioned above. The enrichment of these metabolites is mainly involved in biosynthesis of flavonoid, anthocyanin, and phenylpropanoid. In summary, our study suggests that co-fermentation of quinoa and black barley is a promising approach to enhance the bioactivity of grains.