Biotransformation and metabolism of three methyl salicylate glycosides by gut microbiota in vitro

MSTG-A, MSTG-B and Gualtherin are three natural methyl salicylate glycosides isolated from Dianbaizhu (Gaultheria leucocarpa var. yunnanensis), which is a traditional Chinese folk medicine widely used for the treatment of rheumatoid arthritis. They share the same mother nucleus with aspirin, exhibit similar activity and have fewer side effects. In this study, the incubation of MSTG-A, MSTG-B and gaultherin monomers with human fecal microbiota (HFM), microbiota in 4 intestinal segments (jejunum, ileum, cecal, and colon) and feces of rats in vitro was carried out to comprehensively and meticulously understand their metabolism by gut microbiota (GM) in the body. MSTG-A, MSTG-B and Gualtherin were hydrolyzed by GM to lose glycosyl moieties. The quantity and position of xylosyl moiety significantly affected the rate and extent of the three components being metabolized. The -glc-xyl fragments of these three components could not be hydrolyzed and broken by GM. In addition, the existence of terminal xylosyl moiety prolonged the degradation time. Different results appeared in metabolism of the three monomers by microbiota of different intestinal segments and feces due to the alternation of the species and abundance of microorganisms along the longitudinal axis of the intestinal lumen. Cecal microbiota had strongest degradation ability on these three components. The metabolic details of GM on MSTG-A, MSTG-B and Gualtherin were clarified in this study, providing data support and basis for clinical development and bioavailability improvement.