Biotransformation and metabolic profile of caudatin-2,6-dideoxy-3-O-methy-β-d-cymaropyranoside with human intestinal microflora by liquid chromatography quadrupole time-of-flight mass spectrometry.

In our previous studies, caudatin-2,6-dideoxy-3-O-methy-β-d- cymaropyranoside (CDMC) was for the first time isolated from Cynanchum auriculatum Royle ex Wightand and was reported to possess a wide range of biological activities. However, the routes and metabolites of CDMC produced by intestinal bacteria are not well understood. In this study, ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) technique combined with Metabolynx(TM) software was applied to analyze metabolites of CDMC by human intestinal bacteria. The incubated samples collected for 48 h in an anaerobic incubator and extracted with ethyl acetate were analyzed by UPLC-Q-TOF-MS within 12 min. Eight metabolites were identified based on MS and MS/MS data. The results indicated that hydrolysis, hydrogenation, demethylation and hydroxylation were the major metabolic pathways of CDMC in vitro. Seven strains of bacteria including Bacillus sp. 46, Enterococcus sp. 30 and sp. 45, Escherichia sp. 49A, sp. 64, sp. 68 and sp. 75 were further identified using 16S rRNA gene sequencing owing to their relatively strong metabolic capacity toward CDMC. The present study provides important information about metabolic routes of CDMC and the roles of different intestinal bacteria in the metabolism of CDMC. Moreover, those metabolites might influence the biological effect of CDMC in vivo, which affects the clinical effects of this medicinal plant.