One-step analysis of major bile components in human bile using¹H NMR spectroscopy

Human gallbladder bile dissolved in dimethylsulfoxide provides sharp and resolved signals for major bile components in ¹H NMR spectra. Characteristic well-resolved marker signals that invariably appear in ¹H NMR spectra of bile were identified for cholesterol (H18 methyl signal at 0.643 ppm), lipids (glycerol CH signal at 5.064 ppm), total bile acids (H18 signals in the range 0.520-0.626 ppm), total glycine conjugated bile acids (NH signal at 6.958 ppm), total taurine conjugated bile acids (NH signal at 7.646 ppm), and urea (NH₂ signal near 5.48 ppm), which enabled their rapid and accurate analysis. Excellent linearity and precision of quantitative analysis was observed for all the identified bile components (R² > 0.99 for all). The method was demonstrated on gallbladder bile from 19 patients with gallbladder diseases. Urea in bile was identified by NMR for the first time and its quantitative analysis, along with several other bile components, is presented. The majority of the bile components could be analyzed in a single step. Accurate and rapid quantification of several bile components noninvasively by using the method presented herein may have far-reaching implications in the study of bile acid metabolism and pathophysiology of various hepatobiliary and gastrointestinal diseases.