Aucubin, an
iridoid glucoside, was investigated to determine whether it has a stimulating effect on
alpha-amanitin excretion in
alpha-amanitin intoxicated rats, and whether there is binding activity to
calf thymus DNA. High-performance liquid chromatography (HPLC) analysis of
alpha-amanitin in rat urine allowed quantitative measurement of the
alpha-amanitin concentration with a detection limit of 50 ng/ml. In this system, a group treated with both
alpha-amanitin and
aucubin showed that
alpha-amanitin was excreted about 1.4 times faster than in the
alpha-amanitin only treated group. Our previous results showed that the toxicity of
alpha-amanitin is due to specific inhibition of
RNA polymerase activity and the resultant blockage of the synthesis of certain
RNA species in the nucleus. However, no significant activity change on
RNA polymerase from Hep G2 cells was observed when
aucubin was treated with
alpha-amanitin at any concentration tested. Nevertheless,
aucubigenin inhibited both
DNA polymerase (IC50, 80.5 microg/ml) and
RNA polymerase (IC50, 135.0 microg/ml) from the Hep G2 cells. The potential of both
alpha-amanitin and
aucubin to interact with
DNA were examined by spectrophotometric analysis.
Alpha-Amanitin showed no significant binding capacity to
calf thymus DNA, but
aucubin was found to interact with
DNA, and the apparent binding constant (Kapp) and apparent number of binding sites per
DNA phosphate (Bapp) were 0.45 x 10(4) M(-1) and 1.25, respectively.