Further studies on a human intestinal bacterium Ruminococcus sp. END-1 for transformation of plant lignans to mammalian lignans.

A human intestinal bacterium Ruminococcus (R.) sp. END-1 capable of oxidizing (-)-enterodiol to (-)-enterolactone, enantioselectively, was further investigated from the perspective of transformation of plant lignans to mammalian lignans; A cell-free extract of the bacterium transformed (-)-enterodiol to (-)-enterolactone through an intermediate, enterolactol. The bacterium showed not only oxidation but also demethylation and deglucosylation activities for plant lignans. Arctiin and secoisolariciresinol diglucoside were converted to (-)-dihydroxyenterolactone and (+)-dihydroxyenterodiol, respectively. Moreover, by coincubation with Eggerthella sp. SDG-2, the bacterium transformed arctiin and secoisolariciresinol diglucoside to (-)-enterolactone and (+)-enterodiol, respectively.