Identification of the characteristic chemical constituents in fermented Toona sinensis buds and exploration of their hypoglycemic efficacy by widely targeted metabolomics

Toona sinensis is a unique perennial deciduous tree in China, and its buds are popular vegetables with unique flavors and high nutritional value. In this study, we produced fermented T. sinensis buds using a commercial strain of Lactiplantibacillus plantarum and utilized widely targeted metabolomics to investigate the effect of each Lactobacillus fermentation method on the metabolite composition of fermented T. sinensis buds. Multivariate analysis revealed a significant difference in the metabolic profile between each fermented T. sinensis bud group and the control group. The metabolite profiles of T. sinensis buds fermented for 48 h and 68 h were similar, but both differed significantly from the metabolite profiles of T. sinensis buds fermented for 0 h. Compared with the control group, the T. sinensis buds fermented for 48 h and 68 h had high levels of flavonoids, alkaloids and lipids. In addition, the hypoglycemia test data showed that fermentation significantly increased the ability of T. sinensis buds to inhibit α-amylase and α-glucosidase activities, and the extract of fermented T. sinensis buds significantly improved glucose uptake by IR-HepG2 cells. This study suggests that metabolomics is an effective approach for revealing the differences in metabolite profiles in T. sinensis buds fermented for different durations and is useful for clarifying the mechanism by which fermented T. sinensis buds enhance hypoglycemic activity.