Abstract
Species and numbers of intestinal bacteria have recently been investigated and the
biochemical interaction between a host and its intestinal flora has become the object
of research. It has been suggested that the purgative activities of Rhei rhizoma and Sennae folium are related to the intestinal bacterial action. The present study was undertaken to
reveal the process of the metabolism of sennosides, the main effective components
of these crude drugs, by human intestinal bacteria, to account for the relation between
their defaecation effect and intestinal flora. Through a qualitative study of the
ability of 20 species of anaerobes to metabolize sennoside A (A), species were classified
into four types: Type I possessing ß-glucosidase activity to produce sennidin, Type
II isomerizing A to sennoside B (B), Type III producing unknown glucosides, and Type
IV possessing no metabolic activity. Quantitative analyses of intermediates and products
clarified the process of the metabolism of A. Type I bacterium, using Clostridium sphenoides as a typical example, reductively cleaved A to produce 8-glucosylrheinanthrone (8GRA),
which was then hydrolyzed by ß-glucosidase to produce rheinanthrone (RA), which was
rapidly oxidized to sennidin. Type II bacterium, using Eubacte-rium rectale, reduced both A and B to 8GRA in the same way as Type I bacteria, followed by oxidation
to the isomers B and A, because of deficiency of ß-glucosidase activity. The active
principle is probably RA, which can be formed by Type I bacteria through the reduction
and subsequent hydrolysis of sennosides. The individual differences of Type I bacteria
in the purgative effect of sennosides may be due to the difference of Type I bacteria
in the intestinal flora.
Key Word Index
Rheum palmatum - Cassia acutifolia - Polygonaceae - Caesal-piniaceae - Sennosides
- Rheinanthrone - Purgative Effect - Anaerobes - Human Intestinal Bacteria, Metabolism.
