Role of the gut microbiota in determining the metabolic fate of free and bound phenolic compounds in wheat bran

Wheat bran is widely used in the commercial bakery and cereal snacks to improve the health benefits. The prebiotic effect of wheat bran is associated with its phenolic compound content, composition as well as forms of existence. However, the role of intestinal microbiota in the metabolism of free and bound phenols in wheat bran has rarely been reported. This study investigated the role of intestinal microbiota in the metabolism of different forms of seven individual phenolics in brans of different wheat varieties. The bioaccessibility of total phenols was significantly lower in the upper gastrointestinal digestion tract (2.75% to 18.56%) compared to the bioaccessibility in the colon (92.55% on average). The addition of wheat bran digesta significantly increase the abundance of beneficial bacteria such as Bifidobacterium , Acidaminococcus and Faecalibacterium . However, the correlation analysis showed that Bifidobacterium played a role in the metabolism of free phenolic compounds, while Phascolarctobacterium was associated with the metabolism of bound phenolic compounds. In summary, higher content of bound phenolics was positively related with prebiotic effect. This suggests that when selecting wheat bran as a potential prebiotic, attention should be paid to the phenolic compound composition and their forms of existence. • The prebiotic effects of wheat bran are associated with the phenols’ existence forms. • Free and bound phenols are associated with different bacteria. • The dynamic metabolic changes of different phenol forms are elucidated.