M Ethod for the Quantitative Assay of Fatty Acid–bile Acid Conjugates by Tandem Mass Spectrometry

Fatty acid-bile acid conjugates and especially arachidyl amido cholic acid are synthetic molecules that were shown to prevent cholesterol gallstone formation in mice and hamsters as well as to dissolve pre-existing gallstones in mice. To measure these novel compounds we developed a liquid chromatography electrospray tandem mass spectrometry method based on the analysis of 100 microL of plasma with stearyl amido cholic acid (stamchol, 1.5 microM/L) added as internal standard. Repeatable calibrations between 0 and 50 microM/L exhibited consistent linearity and reproducibility. Inter- and intraassay C.V.s were 5.3-11.4% and 2.6-6.4%, respectively, at targeted concentrations of 0.1, 2.3 and 50 microM/L.