Metabolite profiling, antioxidant and α-glucosidase inhibitory activities of buckwheat processed by solid-state fermentation with Eurotium cristatum YL-1

Buckwheat was processed by solid-state fermentation (SSF) with the probiotic fungal strain Eurotium cristatum YL-1. The effects of SSF on the phytochemical content, as well as the antioxidant and α-glucosidase inhibitory activities, on buckwheat were revealed. Metabolite differences between non-fermented buckwheat (BW) and E. cristatum fermented buckwheat (FBW) were investigated by LC-MS/MS-based untargeted metabolomics. Results showed that 103 and 68 metabolites remarkably differed between BW and FBW in positive and negative ionization modes, respectively. Most phenolic compounds and alkaloids were significantly up-regulated during SSF. Hydrolytic enzymes (i.e., β-glucosidase, α-amylase, protease, and cellulase) were produced by the filamentous fungus E. cristatum during SSF. In vitro spectrophotometric assays demonstrated that the total phenolics content, ferric reducing antioxidant power, reducing power, scavenging activities of DPPH radical and ABTS+, and α-glucosidase inhibitory activity of buckwheat were considerably enhanced after processing by SSF with E. cristatum. Additionally, solvents with different polarities significantly influenced the antioxidant and α-glucosidase inhibitory activities of buckwheat extracts. Our study indicated that processing by SSF with E. cristatum can greatly improve the phytochemical components of buckwheat and consequently contribute to its antioxidant and α-glucosidase inhibitory activities. SSF with E. cristatum is an innovative method for enhancing the health-promoting components and bioactivities of buckwheat.