Isolation and identification of metabolites from dihydromyricetin

Dihydromyricetin (DHM) is the major bioactive constituent of Rattan Tea, which is the tender stems and leaves of Ampelopsis grossendentata . Seven metabolites (2–8) of DHM (1) were obtained by the chromatographic method. The metabolites 2–5 were obtained from the urine of rats administered orally with DHM; and metabolites 6–8 were detected in the fecal specimens of rats, which were also produced by human intestinal bacteria (HIB) in vitro , and were separated from the cultured media of HIB containing DHM. Their structures were elucidated as 5,7,3′,5′‐tetrahydroxyflavanonol (2); 5,7,3′,5′‐tetrahydroxy‐4′‐methoxyflavanonol (3); 5,7,4′,5′‐tetrahydroxy‐3′‐methoxyflavanonol (4); and dihydromyricetin‐ O ‐5‐β‐ D ‐glucuronide (5); (2 R ,3 S )‐5,7,3′,4′,5′‐pentahydroxyflavanonol (6); 3,4,5,7,3′,4′,5′‐hepthydroxyflavan (7) and 5,7,3′,4′,5′‐pentahydroxyflavanone (8) on the basis of UV, NMR and LC‐MS/MS data. These seven metabolites were formed through familiar metabolic reactions. Dihydromyricetin‐ O ‐5‐β‐ D ‐glucuronide (5) is a new compound. The 13 C‐NMR data of (2) and (4) are reported for the first time. Copyright © 2007 John Wiley & Sons, Ltd.