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.