Degradation of flavonoid aglycones by rabbit, rat and human fecal flora

The degradation of thirteen flavonoid aglycones - wogonin, diosmetin, hesperetin, baicalein, morin, genistein, daidzein, quercetin, naringenin, luteolin, kaempferol, apigenin and neophellamuretin - were investigated in rabbit, rat and human fecal flora suspensions as well as in artificial intestinal juice, using high performance liquid chromatography. Separation were performed with a Cosmosil 5C₁₈-AR II column by isocratic and gradient elution with 0.1% (v/v) phosphoric acid-acetonitrile as a mobile phase, and detected at 254 nm. The flow rate was 1.0 ml/min. 5,7-Dimethoxycoumarin was used as the internal standard. The result indicated that all flavonoid aglycones except baicalein, diosmetin and quercetin were quite stable in artificial intestinal juice, whereas all were degraded in rabbit, rat and human feces suspension. In rabbit feces, wogonin, diosmetin and hesperetin were less degraded, whereas neophellamuretin, apigenin, kaempferol, luteolin, and naringenin were the most extensively degraded. In rat feces, wogonin and diosmetin were least degraded, whereas kaempferol, quercetin, genistein, luteolin, naringenin and neophellamuretin were extensively degraded. As in human feces, wogonin, daidzein and diosmetin were less degraded, whereas morin, genistein, baicalein, and quercetin were extensively degraded. In conclusion, wogonin and diosmetin were among the less degraded ones for all three feces tested. The presence of a methoxy group on the A or B ring of the flavonoid seems to protect the structure from bacterial degradation.