The Complex Interplay between Botanical Supplements and the Human Gut Microbiome

Botanical supplements have been used for the prevention and treatment of human diseases since ancient times and remain important, widely consumed therapeutics. While they display promising efficacy across a broad spectrum of biological activities, poor oral bioavailability often limits their utility. Upon ingestion, these compounds may remain in the gastrointestinal tract prior to absorption, during which time they interact with gut microbiota. These interactions can significantly alter their bioavailability since microbial enzymes, known for their wide substrate specificity, are capable of readily transforming xenobiotics, often changing their biological activity as well as their bioavailability. Herein, we summarize the chemistry of microbial biotransformations of botanical supplements, highlighting key enzymatic transformations. The reciprocal interactions between four widely used botanical supplements and the human gut microbiome are outlined including green tea, açai, red wine, and mangosteen. Their microbial metabolism and modulation of human gut microbiota is discussed, highlighting the various enzymes and metabolites reported from relevant literature. Although the direct effect of microbiome bioconversion of botanical supplements is largely unexplored due to the complexity of both systems, this review provides a framework for research to determine the bidirectional effects of botanicals and gut microbiota on human health.