Sudies On The In Vivo Metabolism Of Cinobufagin In Rat And The Comparative Metabolic Species Difference In Vitro

Objective: Studies on the in vivo, in vitro metabolism and excretion of cinobufagin (CB) which is the major active component in Traditional Chinese Medicine Chansu are aim to reveal the major biological active derivative(s) of cinobufagin in vivo.Methods: (1) In vivo experiments: investigation of the biliary excretion of cinobufagin in rat; (2) In vitro experiments: investigation of the comparative metabolism of cinobufagin in liver microsomes from human and usual experimental animals including mouse, rat, dog, minipig and monkey; (3) To reveal the metabolic pathway of CB by the phytochemical and spectroscopy methods; (4) To evaluate the anticancer activities of cinobufagin and its metabolites by MTT method.Results: The metabolites of cinobufagin in rat bile were almost the mono- or dihydroxy-3-epi-deacetylcinobufagin and their anticancer activities reduced signi- ficantly compared with cinobufagin. Hydroxylation was identified as the prominent metabolic pathway of cinobufagin in human, monkey, dog, minipig liver and minipig was commended to a surrogate model for DMPK studies of CB in the future. In addition, the anticancer activities of the major metabolites of cinobufagin, namely 1a-hydroxycinobufagin and 5β-hydroxycinobufagin reduced by a relatively slight degree compared with cinobufagin.Conclusions: There was significant species difference in the clearance behaviors of cinobufagin in human and rat liver: the species-specific deacetylation and epimerization combined hydroxylation existed in RLM, while hydroxylation was a major pathway in HLM, MLM, DLM, PLM and CyLM. The anticancer activities of cinobufagin would be reduced by the metabolism no matter in human or in monkey, dog, pig, rat and mouse.