A new, major C₂₇ biliary bile acid in the Red-winged tinamou (Rhynchotus rufescens): (25R)-1β,3α, 7α-trihydroxy-5β-cholestan-27-oic acid

The chemical structures of the three major bile acids present in the gallbladder bile of the Red-winged tinamou (Rhynchotus rufescens), an early evolving, ground-living bird related to ratites, were determined. Bile acids were isolated by preparative reversed-phase HPLC. Two of the compounds were identified as the taurine N-acylamidates of (25R)-3α,7α-dihydroxy-5β-cholestan-27-oic acid (constituting 22% of biliary bile acids) and (25R)-3α,7α,12α-trihydroxy-5β-cholestan-27-oic acid (constituting 51%). The remaining compound, constituting 21% of biliary bile acids, was an unknown C₂₇ bile acid. Its structure was elucidated by LC/ESIMS/MS and NMR and shown to be the taurine conjugate of (25R)-1β,3α,7α-trihydroxy-5β-cholestan-27-oic acid, a C₂₇ trihydroxy bile acid not previously reported. Although C₂₇ bile acids with a 1b-hydroxyl group have been identified as trace bile acids in the alligator, this is the first report of a major biliary C₂₇ bile acid possessing a 1b-hydroxyl group.