H. Schneider et al., Anaerobic transformation of quercetin-3-glucoside by bacteria from the human intestinal tract, ARCH MICROB, 171(2), 1999, pp. 81-91
From human feces two phenotypically differ ent types of bacteria were isola
ted on quercetin-3-glucoside as carbon and energy source. Isolates of one t
ype were identified as strains of Enterococcus casseliflavus. They utilized
the sugar moiety of the glycoside, but did not degrade the aglycon further
. The sugar moiety (4 mM) was fermented to 5.5 +/- 2.1 mM formate, 2.1 +/-
0.7 mM acetate, 1.6 +/- 0.3 mM L-lactate, and 1.3 +/- 0.4 mM ethanol. The s
econd type of isolate was identified as Eubacterium ramulus. This organism
was capable of degrading the aromatic ring system. Growing cultures of Euba
cterium ramulus converted 5 mM quercetin-3-glucoside to 1.7 +/- 0.6 mM 3,4-
dihydroxyphenylacetic acid, 7.6 +/- 1.0 mM acetate, and 4.0 +/- 0.4 mM buty
rate. Molecular hydrogen, 3,4-dihydroxybenzaldehyde, and ethanol were detec
ted in small amounts. Phloroglucinol was a transient intermediate in the br
eakdown of quercetin-3-glucoside. Eubacterium ramulus did nor grow on the a
glycon quercetin or the ring-fission intermediate phloroglucinol, but cleav
ed the flavonoid ring system when glucose was present as a cosubstrate. The
most probable number of quercetin-3-glucoside-degrading bacteria determine
d in nine human fecal samples was 10(7)-10(9)/g dry mass. Isolates from the
se experiments were all identified as Eubacterium ramulus.