Deglycosylation and absorption of marein, flavanomarein and taxifolin-7-O-β-D-glucopyranoside from capitula of Coreopsis tinctoria in rats and humans

Marein, flavanomarein and taxifolin-7-O-β-D-glucopyranoside (TDG) are functional compounds in capitula of Coreopsis tinctoria (CCT). This study demonstrated the above glycosides could be partially deglycosylated to okanin, isookanin and taxifolin, respectively, in cell free extracts from rat and human small intestine, human colon, but not from stomach and cecum. Okanin and isookanin mainly occurred as glucuronide conjugates; whereas taxifolin was in sulfate in rat plasma. The exposures of the glycosides and aglycones were positively correlated with the dosages of CCT extract in rats after oral administration. The aglycones but not glycosides were detected in the plasma of healthy volunteers after intake of CCT (2.5 g/50 kg) water solution. In conclusion, marein, flavanomarein and TDG could be deglycosylated to respective aglycones in gastrointestinal tracts, which could be absorbed and biotransformed to glucuronide or sulfate conjugates. The results will help us to better understand the function and functional components of CCT in vivo.