Biliary bile acids in birds of the Cotingidae family: Taurine-conjugated (24 R,25 R)-3α,7α,24-trihydroxy-5β-cholestan-27-oic acid and two epimers (25 R and 25 S) of 3α,7α-dihydroxy-5β-cholestan-27-oic acid

Abstract

Three C 27 bile acids were found to be major biliary bile acids in the capuchinbird ( Perissocephalus tricolor) and bare-throated bellbird ( Procnias nudicollis), both members of the Cotingidae family of the order Passeriformes. The individual bile acids were isolated by preparative RP-HPLC, and their structures were established by RP-HPLC, LC/ESI-MS/MS and NMR as well as by a comparison of their chromatographic properties with those of authentic reference standards of their 12α-hydroxy derivatives. The most abundant bile acid present in the capuchinbird bile was the taurine conjugate of C 27 (24 R,25 R)-3α,7α,24-trihydroxy-5β-cholestan-27-oic acid, a diastereomer not previously identified as a natural bile acid. The four diastereomers of taurine-conjugated (24 ξ,25 ξ)-3α,7α,24-trihydroxy-5β-cholestan-27-oic acid could be distinguished by NMR and were resolved by RP-HPLC. The RRT of the diastereomers (with taurocholic acid as 1.0) were found to be increased in the following order: (24 R,25 R) < (24 S,25 R) < (24 S,25 S) < (24 R,25 S). Two epimers (25 R and 25 S) of C 27 3α,7α-dihydroxy-5β-cholestan-27-oic acid were also present (as the taurine conjugates) in both bird species. Epimers of the two compounds could be distinguished by their NMR spectra and resolved by RP-HPLC with the (25 S)-epimer eluting before the (25 R)-epimer. Characterization of the taurine-conjugated (24 R,25 R)-3α,7α,24-trihydroxy-5β-cholestan-27-oic acid and two epimers (25 R and 25 S) of 3α,7α-dihydroxy-5β-cholestan-27-oic acid should facilitate their detection in peroxisomal disease and inborn errors of bile acid biosynthesis.