Gut bacteria-derived 5-hydroxyindole: a potent stimulant of gastrointestinal motility

Microbial conversion of dietary or drug substrates into small bioactive molecules represents a regulatory mechanism by which the gut microbiota alters intestinal physiology. Here, we show that a wide variety of gut bacteria can metabolize the dietary supplement, and antidepressant 5-hydroxytryptophan to 5-hydroxyindole via the tryptophanase enzyme. Oral administration of 5-hydroxytryptophan results in detection of 5-hydroxyindole in fecal samples of healthy volunteers with inter-individual variation.