Microbial metabolites of tryptophan in the

intestinal tract with special reference to skatole1 ’ 2 Melvin T. Yokoyama,3 Ph.D. and James R. Carlson,4 Ph.D. Since 1900, researchers have been studying the microbial metabolites of tryptophan in the intestinal tract, and have recognized the potential toxic effects of these metabolites to the host. As early as 1868, Senator (1) pro-posed the “theory ofautointoxication, ” based on the belief that the degradation of proteins in the intestine produced substances which were toxic to the host. The literature indicates that the search for the precursor of one of these metabolites, indole, lead to the discov-cry of the amino acid, tryptophan, by Hop