Dietary Epigallocatechin-3-Gallate Supplementation Decreases Indole-3-Propionic Acid and Increases Indole-3-Lactic Acid in Rat Cecal Contents

This study investigated the effect of epigallocatechin-3-gallate (EGCG), a major polyphenol in green tea, on the cecal levels of microbial metabolites of tryptophan (Trp) in rats. Rats were fed either a control diet or a diet containing 0.25% (w/w) EGCG for 1 wk. The results showed that dietary EGCG treatment increased the concentration of indole-3-lactic acid while decreasing indole-3-propionic acid in the cecal contents compared to the control group. Furthermore, analysis of fecal microbial composition by 16S rRNA gene sequencing revealed that EGCG supplementation reduced the relative abundance of the genus Clostridium. This study provides fundamental insights into the role of EGCG in modulating the production of biologically active Trp metabolites.