Collected human intestinal flora (whole bacteria) was incubated with glycyrrhizin (GL), glycyrrhetic acid (GA), glycyrrhetic acid monoglucuronide (GAMG) and a combination of the three for 10 min at 37°C under pH 5.6 and 7.0. The effect of these components on GL β-D-glucuronidase activity, GAMG β-D-glucuronidase activity and metabolite production in whole bacteria was examined. GL and GA were not metabolized at pH 5.6 and 7.0 by whole bacteria, while the level of GAMG changed at both pH 5.6 and 7.0. However, preincubated whole bacteria converted GA and a combination containing GA to other metabolites removed 3α-hydroxyglycyrrhetic acid and 3-oxoglycyrrhetic acid. The level of GL β-D-glucuronidase activity remaining in whole bacteria after exposure to both GA and GAMG was above its initial level at pH 5.6 and 7.0, and the level of GAMG β-D-glucuronidase activity remaining after exposure to GL, GA and GAMG was suppressed against control at pH 5.6 and 7.0. It is found that intestinal bacteria had similar action against GL, GA and GAMG at between pH 5.6 and 7.0.