Gut Microbiota: A Pivotal Hub for Polyphenols as Antidepressants.

Polyphenols, present in a broad range of plants, have been thought to be responsible for many beneficial health effects, such as anti-depressant. Despite polyphenols can be absorbed in small intestine directly, most of them have low bioavailability and reach the large intestine without any modifications due to their complex structures. The interactions between microbial communities and polyphenols in the intestine is important for the latter to exert antidepressant effects. Gut microbiota can improve the bioavailability of polyphenols, in turn, polyphenols can maintain the intestinal barrier, as well as the community of the gut microbiota in normal status. Furthermore, gut microbita catabolize polyphenols to more active, better-absorbed metabolites, further ameliorate depression through the microbial-gut-brain (MGB) axis. Based on these evidences, the review illustrated the potential role of gut microbiota in the processes of polyphenols or their metabolites acting as antidepressants, and further envisioned the gut microbiota as the therapeutic targets for depression.