Abstract
【Purpose】Roasted burdock root tea (BT), rich in inulin and chlorogenic acid, is currently being established as a tea beverage in Japan and a wider area. This study aimed to clarify the effects of BT on the gut microbiota and gut putrefactive products and blood ammonia levels.
【Methods】BT was prepared using 5% (w/v) dried burdock root. Human fecal slurry was inoculated into 1/4 medium prepared with distilled water or BT, and after 24h anaerobic incubation, pH and putrefactive products (ammonia, indole, phenol) were measured. After administration of BT as drinking water to ICR mice on a high-sucrose and low-dietary fibre diet for 14 days, organic acid and ammonia concentrations in the cecum and blood ammonia concentrations were measured, and the fecal flora was analyzed using 16S rDNA (V4) amplicon sequencing.
【Result】In human faecal cultures established using a medium prepared with BT, the pH significantly decreased from 6.5 to 4.6. In vitro, BT significantly suppressed the production of ammonia and indole (p < 0.05). In vivo, BT increased the caecal acetate level from 34 μmol/g to 49 μmol/g and n-butyrate level from 5.1 μmol/g to 14 μmol/g and reduced the caecal pH from 7.0 to 6.6. Despite no significant changes in caecal ammonia levels, plasma ammonia levels in BT-treated mice decreased from 0.74 to 0.50 μmol/mL. Moreover, 16S rDNA (V4) amplicon sequencing of faeces revealed that BT increased the short-chain fatty acid-producing gut commensals Muribaculaceae and Clostridia UCG-014. These results suggest that BT has desirable functional properties correlated with short-chain fatty acid production and pH-lowering effects that inhibit ammonia production and absorption in the gut.
