Hydrolysis of dietary flavonoid glycosides by strains of intestinal Bacteroides from humans.

Rutin and quercitrin are hydrolysed to quercetin, and robinin is hydrolysed to kaempferol, by faecal flora from healthy subjects. The enzymes required for these hydrolyses, namely alpha-rhamnosidase and beta-galactosidase, were produced by some strains of Bacteroides distasonis; other strains, however, synthesized beta-glucosidase. The last-named enzyme was also elaborated by Bacteroides uniformis and Bacteroides ovatus. All the enzymes were produced constitutively. A cell-free extract of B. distasonis containing beta-glucosidase displayed an enzymic activity of 1 mumol/10 min per 10 mg of protein.