An UPLC-MS/MS method for targeted analysis of microbial and host tryptophan metabolism after administration of polysaccharides from Atractylodes macrocephala Koidz. in ulcerative colitis mice

Botanic polysaccharides can be metabolized by gut microbiota into short-chain fatty acids (SCFAs) to exert extensive bioactivities, yet targeted analysis of the effect of botanic polysaccharides on other gut microbial metabolites is scarcely seen. Tryptophan metabolites such as indole and indole derivatives play import roles in health and disease development. Using polysaccharides from Atractylodes macrocephala Koidz. (AMP) in treating ulcerative colitis as the example, we checked the effects of AMP on tryptophan metabolites. After examination of pharmacological effects of AMP, we established an ultra-performance liquid chromatography coupled with mass spectrometry/mass spectrometry (UPLC-MS/MS) method to simultaneously determinate the levels of 30 tryptophan metabolites and used the method to determine the levels of these metabolites in feces and plasma. The detection results showed that 12 metabolites in feces can be detected, and 17 metabolites can be detected in plasma samples. In addition, we found out that total levels of aryl hydrocarbon receptor ligands were decreased in colitis model whereas AMP treatment can increase the levels of total ligands in both feces and plasma. The results indicated that the therapeutical effect of AMP on colitis was associated with modulation of fecal and host tryptophan metabolism. This study provides new insight into the molecular mechanisms of polysaccharides that the beneficial effects of polysaccharides can be achieved by modulating microbial tryptophan metabolism in addition to SCFAs.