Vulpecholic acid (1α,3α,7α-trihydroxy-5β-cholan-24-oic acid): A novel bile acid of a marsupial, Trichosurus vulpecula (Lesson)

A novel trihydroxylated C 24 bile acid was isolated from the gallbladder bile of the Australian opossum, Trichosurus vulpecula (Lesson). This acid, for which the name vulpecholic acid is proposed, was identified as 1α,3α,7α-trihydroxy-5β-cholan-24-oic. The structure proof included mass spectral and 1H and 13C nuclear magnetic resonance characterization of all crucial derivatives obtained by: a) oxidation of the methyl ester to a triketone with the enolizable 1,3-diketone function; b) methylation of this triketone to two isomeric methyl enol ethers; and c) reductive removal of oxygen functions from this triketone to give 5β-cholan-24-oic and 7-oxo-5β-cholan-24-oic acids. Vulpecholic acid was found in the bile in the unconjugated form; it accounted for more than 60% of the solid bile material. The marsupial T. vulpecula is the first example of a mammal secreting a 1α-hydroxylated bile acid as well as the first example of a mammal secreting the major bile acid in a free form.link_to_subscribed_fulltex

Bile acids of marsupials. 2. Hepatic formation of vulpecholic acid (1α,3α,7α-trihydroxy-5β-cholan-24-oic acid) from chenodeoxycholic acid in a marsupial, Trichosurus vulpecula (Lesson)

Free vulpecholic acid (1α,3α,7α-trihydroxy-5β-cholan-24-oic) is the major biliary component of the Australian opossum (Trichosurus vulpecula), accompanied only by a few percent of its taurine conjugate. In order to exclude a microbial involvement in its formation (i.e., secondary origin) four sets of experiments were performed. It was found that a) the level of vulpecholic acid remained unchanged in the bile of opossums fed with neomycin and kanamycin for 7 days prior to bile collection; b) it also remained unchanged after long bile drainage; c) in opossums prepared with biliary cannula, intraportally injected [24- 14C]chenodeoxycholic acid was transformed to [24- 14C]vulpecholic acid; and d) in a similar experiment, the detectable transformation of [1α,2α- 3H 2]cholesterol to vulpecholic acid was observed. In experiment c) 28-66% of the administered radioactivity was secreted in 2 h in the form of free biliary vulpecholic and chenodeoxycholic acids. Only a trace amount of the corresponding taurine conjugates (~0.4%) was formed. Moreover, rapidly declining specific radioactivity of the unconjugated chenodeoxycholic acid indicated its probable participation in the native formation of vulpecholic acid.link_to_subscribed_fulltex