Roasting enhances antioxidant, anti‐glycation, and gut microbiota‐modulating activities of burdock root tea in mice fed a high‐sucrose, low‐fibre diet

BACKGROUND Although burdock tea is widely consumed for its health benefits, the impact of roasting on its bioactive composition and gut microbiota‐modulating effects remains unclear. We examined the effects of roasting on the functional properties of burdock root tea in vitro and its modulatory effects on the gut microbiota. Burdock tea was prepared without (BT) or with (RBT) roasting. RESULTS The total phenolic content in the hot‐water extract solution of RBT (85 μmol catechin equivalents g −1 sample) was threefold higher than that of BT ( P < 0.05). The superoxide anion radical scavenging capacity and Fe‐reducing power were significantly increased by roasting. The anti‐glycation activity of the bovine serum albumin–methyl glyoxal model was also increased by roasting. BT and RBT showed similar anti‐inflammatory effects on lipopolysaccharide‐induced nitrite oxide secretion in murine macrophage‐like RAW264.7 cell culture. Compared with mice fed high sucrose and low dietary fibre, faecal excretion was increased in mice fed a diet containing 5% (w/w) RBT rather than BT. Among the faecal microbiota, multi‐polysaccharide‐degrading bacteria, such as Prevotellamassilia timonensis‐ , Duncaniella dubosii ‐, Bacteroides uniformis ‐, and Phocaeicola vulgatus‐ like bacteria were higher in mice fed RBT than in those fed BT. Metabolic pathway prediction using Tax4Fun2 and Kyoto Encyclopedia of Genes and Genomes showed that other glycan degradation (ko0051) was higher in the microbiota of mice fed RBT than in those fed BT. CONCLUSION These results suggest that roasting BT increases beneficial functional activities and gut microbiota modulation, which may be useful for developing functional beverages and health‐promoting foods.