Studies on Steroids

Complete 1H and 13C resonance assignments of glycosidic conjugates of non‐amidated and amidated bile acids

“…3,9,14 Thus, glycosidation at the 3-, 6-or 7-position in the 5ˇ-steroid nucleus and amidation at the 24-position in the side-chain are possible candidates for bile acid metabolism in humans and naturally occurring conjugated bile acids are composed of a complex mixture of the single and double conjugates of non-amidated and amidated bile acid glycosides. In the 1D 1 H NMR spectra of 1-7, the following proton signals were assigned from previous NMR studies of related steroids 21,22 and carbohydrates: 23 -25 The combined use of 1 H-1 H and 1 H-13 C shift-correlated 2D NMR techniques is now well recognized as a powerful and reliable tool for the structural and stereochemical elucidation of complex steroid conjugates.…”

“…In addition to the glycosidic conjugation of bile acids which is bonded by an ether linkage with a hydroxyl group in the 5ˇ-steroid nucleus, an additional conjugation on the C-24 terminal carboxyl group in the side-chain with glycine or taurine results in the formation of polar and hydrophilic double-conjugated bile acids. 3,9,14 The structures of conjugated bile acids in biological fluids have been exclusively identified by gas chromatographic-mass spectrometric (GC-MS) analysis, after deconjugation of both amino acid and sugar moieties by chemical or enzymatic treatments. However, the deconjugation procedure has several drawbacks, because it loses information concerning the type, site and number of conjugations.…”