Development of the Detection and Measurement of Bile Acid Ester Glycosides as Markers of Liver Diseases in Humans

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An efficient synthesis of the carboxyl-linked glucosides of bile acids was described. Direct esterification of unprotected bile acids with 2,3,4,6-tetra-O-benzyl-D-glucopyranose in pyridine in the presence of 2-chloro-1,3,5-trinitrobenzene as a coupling agent afforded a mixture of the α- and β-anomers (ca. 1 : 4) of the 1-O-acyl-D-glucoside benzyl ethers of bile acids, which was effectively separated on a C_<18> reversed-phase chromatography. Subsequent hydrogenolysis of the α- and β-acyl glucoside benzyl ethers on a 10% Pd/C catalyst at atomospheric pressure gave the corresponding free esters. A facile hydrolysis and transesterification of the acyl glucosides in various solvents were also revealed.A method for the separation of a mixture of different series of ionic, high polar, and hydrophilic conjugates of bile acid ester glucosides by indusion high performance liquid chromatography (HPLC) with methyl β-cyclodextrin or by ion-pair HPLC with an ion-pair chromatographic reagent, di-n-butylamine acetate (DBAA), as mobile phase additives. Satisfactory chromatographic separation and column performance were attained by the indusion HPLC and ion-pair HPLC methods. The present methods provide an insight into the separation and structural elucidation of biologically important bile acid ester glucosides.