No abstract

The metabolism of sennosides is discussed in view of the results obtained during the last years. Rhein anthrone is to be considered as the ultimate active form produced by microorganisms in the colon. Several contributions of this senna symposium bring complementary information of utmost interest.

After single intracaecal administration of [14C]rhein (25 mg kg-1) and [14C]rhein anthrone (20 mg kg-1) to rats, the summated recovery rates of 14C after five days were in urine 37(+/- 8.3)% and 2.8(+/- 0.4)% and in faeces 53(+/- 9.5)% and 95 (+/- 10.1)%, respectively. The clearance of radioactivity from the organs and tissues was almost complete within three days, with the exception of the kidney which exhibited pronounced retention of radioactivity even after five days (less than 61% of 24 h values). Extracts of faeces from animals treated with [14C]rhein of [14C]rhein anthrone, revealed rhein as well as other radioactive substances, which chemically did not react as 1,8-dihydroxyanthraquinones.

The two radioactive compounds were administered intracaecally to rats, and the recovery rates amounted to 89.9% for ¹⁴C-rhein and to 97.4% for ¹⁴C-rhein anthrone after 5 days. All organs and tissues showed for both compounds a significant clearance of radioactivity with exception of the kidneys where high levels persisted even after 5 days. Different metabolites could be detected in urine as well as in faeces where also nonanthraquinone fractions could be found.