A multiplex HRMS assay for quantifying selected human plasma bile acids as candidate OATP biomarkers.

AIM: Selected bile acids (BAs) in plasma have been proposed as endogenous probes for assessing drug-drug interactions involving hepatic drug transporters such as the organic anion-transporting polypeptides (OATP1B1 and OATP1B3). MATERIALS & METHODS: Plasma extracts were analyzed for selected BAs using a triple TOF API6600 high-resolution mass spectrometer. RESULTS: Glycodeoxycholic acid 3-sulfate, glycochenodeoxycholic acid 3-sulfate, glycodeoxycholic acid 3-O-ß-glucuronide and glycochenodeoxycholic acid 3-O-ß-glucuronide are presented as potential OATP1B1/3 biomarkers. CONCLUSION: Six BAs are quantified in human plasma using a multiplexed high-resolution mass spectrometry method. Glycodeoxycholic acid 3-sulfate and glycodeoxycholic acid 3-O-ß-glucuronide are proposed as potential biomarkers based on observed four- to fivefold increase in plasma AUC (vs placebo), following administration of a compound known to present as an OATP1B1/3 inhibitor in vitro.

The synthesis of glycine conjugated 3-oxo-bile acids.

The glycine conjugates of the 3-oxo-derivatives of lithocholic, deoxycholic, chenodeoxycholic and cholic acids have been synthesized from their respective parent bile acid using established procedures. The reaction sequence involved oxidation using either chromic acid or silver carbonate--Celite followed by a conjugation step employing the peptide coupling reagent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline. The final products were obtained in both high yield and purity for use as reference compounds in the analysis of conjugated bile acids in bile and faecal samples by high performance liquid chromatography. Analysis of the prepared 3-oxo-glycobile acids by fast atom bombardment negative ion mass spectrometry, infrared spectroscopy and nuclear magnetic resonance proton spectroscopy is also discussed along with the thin-layer chromatographic properties.