Hasty effect on the metabolism of glycyrrhizin by Eubacterium sp. GLH with Ruminococcus sp. PO1-3 and Clostridium innocuum ES24-06 of human intestinal bacteria.

Abstract

Eubacterium sp. GLH with Ruminococcus sp. PO1-3 and Clostridium innocuum ES24-06 possessing enzymes involved in the metabolism of glycyrrhizin (GL) was cultured in GAM medium with and without 1.0 mM GL or 1.0 mM glycyrrhetic acid (GA). GL (1.0 mM) enhanced 3alpha-hydroxyglycyrrhetinate (3alpha-hydroxyGA) dehydrogenase activity, GA (1.0 mm) suppressed 3alpha-hydroxyGA dehydrogenase activity, GL beta-D-glucuronidase activity and the mixed bacterial growth, and GL and GA showed almost no change in a lower level of 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity during 5 d of culture. GL (1.0 mM) and GA (1.0 mM) were metabolized to a small amount of GA and a negligible amount of 3-oxo-glycyrrhetic acid (3-oxo-GA) and 3alpha-hydroxyGA, and to a negligible amount of 3-oxo-GA, respectively, by these mixed bacteria. These amounts coincided with those of metabolites produced from 1.0 mM GL and 1.0 mM GA added to these mixed bacteria after 24 h culture. Whole bacteria and sonicated bacteria derived from the collection of these mixed bacteria reached a maximal stage and metabolized GL to a relatively large amount of GA and 3-oxo-GA, and a negligible amount of 3alpha-hydroxyGA and GA to a small amount of 3-oxo-GA and 3alpha-hydroxyGA within 180 min. GL beta-D-glucuronidase with 3beta-HSD and 3alpha-hydroxyGA dehydrogenase partially purified from each bacterium was converted GL to 3alpha-hydroxyGA, producing metabolites of about 60% after 10 min of incubation. These mixed bacteria possessed high enzyme activities could produce the metabolites of GL in under one hour under conditions.