Ononin is a bioactive isoflavone of legumes. To explore the "effective forms" of ononin, its metabolites were characterized using HPLC-ESI-IT-TOF-MSn after oral administration to rats. Metabolites (106), including 94 new metabolites, were characterized, which contained 17 phase I, 23 hydroxylated and methylated, 54 sulfated, 10 glucuronidated, and 2 sulfated and glucuronidated metabolites. Six hydroxylated metabolites of formononetin (aglycone of ononin) were simultaneously detected for the first time. Twenty-three hydroxylated and methylated metabolites were the new metabolites of ononin, and the number of hydroxylation and methylation was 1-3 and 1-2. Twenty metabolites have ononin-related bioactivities, and many metabolites have the same bioactivities. Their probable mechanisms of action may be additive and/or synergistic effects, especially because of the addition of the blood concentrations of these compounds. The results provide a foundation for a better understanding of the "effective forms" of ononin.
Keywords: HPLC−ESI-IT-TOF-MSn; additive effect; effective forms; metabolites; ononin; ononin-related bioactivities.