Anaerobic degradation of flavonoids by Eubacterium ramulus

Eubacterium ramulus, a quercetin-3-glucoside-degrading anaerobic microorgan ism that occurs at numbers of approximately 10(8)/g dry feces in humans, wa s tested for its ability to transform other flavonoids. The organism degrad ed luteolin-7-glucoside, rutin, quercetin, kaempferol, luteolin, eriodictyo l, naringenin, taxifolin, and phloretin to phenolic acids. It hydrolyzed ka empferol-3-sorphoroside-7-glucoside to kaempferol-3-sorphoroside and transf ormed 3,4-dihydroxyphenylacetic acid, a product of anaerobic quercetin degr adation, very slowly to non-aromatic fermentation products. Luteolin-5-gluc oside, diosmetin-7-rutinoside, naringenin-7-neohesperidoside, (+)-catechin, and (-)-epicatechin were not degraded. Cell extracts of E. ramulus contain ed alpha- and beta-D-glucosidase activities, but were devoid of alpha-L-rha mnosidase activity. Based on the degradation patterns of these substrates, a pathway for the degradation of flavonoids by E. ramulus is proposed.