Abstract
Daiokanzoto (DKT), a Kampo medicine that includes the combination of two crude drugs (rhubarb and glycyrrhiza), is clinically effective for constipation. Sennoside A, the main purgative constituent of rhubarb, is a prodrug that is transformed into an active metabolite, rheinanthrone, by β-glucosidase derived from bifidobacteria. Thus far, we have presented evidence that anthraquinones in rhubarb, rhein 8-O-β-D-glucopyranoside (RG) and rhein, contribute to the purgative action of sennoside A by accelerating its metabolic activity. The aim of this study was to clarify the mechanism of action by which anthraquinones accelerate sennoside A metabolism. In pre-incubated fecal suspensions, mixed with anthraquinones, there was significant acceleration of the metabolic activity of sennoside A compared with that in the control. This finding suggested that anthraquinones induced metabolism by bacteria or their enzyme of sennoside A. The mechanism of action by RG was thus further investigated with puromycin, which is a protein synthesis inhibitor, in terms of quantitative or qualitative changes of sennoside A-metabolic enzyme. The results suggested that RG increased the synthesis of sennoside A-metabolic enzyme by bifidobacteria. Therefore, it is assumed that the anthraquinones included in DKT intensified the activation of sennoside A by increasing the synthesis of sennoside A-metabolic enzyme derived from bifidobacteria, which is the main metabolic bacteria.
