Quantification of glycine and taurine conjugated bile acids in human bile using ¹H NMR spectroscopy

A simple method for quantification of conjugated bile acids in human bile using ¹H NMR spectroscopy is presented. Bile acids in human bile are essentially conjugated with either glycine or taurine. The amide NH resonances from the conjugated bile acids are invariably devoid of interfering signals in ¹H NMR spectra. Under physiologic conditions of human bile (pH ∼7.0 to 7.7), amide signal intensities are attenuated due to the chemical exchange and hence quantitative estimation is precluded. In the present study, the quantity of total glycine and taurine conjugated bile acids could be obtained accurately by suppressing the amide exchange by reducing the pH slightly lower than physiologic value (6.0 ± 0.5). Further, the quantity of glycine conjugated bile acids can be calculated accurately by subtracting the quantity of taurine conjugated bile acids from the total conjugated bile acids as determined from the present method.