Metabolism of cinobufagin in rat liver microsomes. Identification of epimerized and deacetylated metabolites by liquid chromatography/mass spectrometry
Zhang, L.S.; Yoshida, T.; Aoki, K.; Kuroiwa, Y.
Drug Metabolism and Disposition the Biological Fate of Chemicals 19(5): 917-919
1991
ISSN/ISBN: 0090-9556 PMID: 1686236 Document Number: 378401
The metabolism of cinobufagin (CB) in rat liver microsomes was studied. By comparison of retention times and fragmentation patterns obtained by thermospray LC/MS with those of authentic standards, four metabolites of CB were also identified, in addition to deacetylCB (M1) and 3-epideacetylCB (M2), which have been reported previously. The additional four metabolites were identified to be 3-epiCB (M4), 3-ketoCB (M5), 3-keto-16 beta-OH-deacetylCB (M3), and 3-keto-16 alpha-OH-deacetylCB (M6). The primary metabolic products of CB were M1 and M2, with a small amount of M4 and trace amounts of M3, M5, and M6. These results indicate that major metabolic routes of CB were deacetylation at the 16-position and epimerization at the 3-position via the 3-keto intermediate.