7 beta,12 beta-Dihydroxy-5 beta-cholan-24-oic acid as an internal standard for quantitative determination of bile...

In order to find an artificial internal standard compound for quantitative determination of bile acids by gas chromatography, 7 alpha,12 alpha-, 7 alpha, 12 beta-, 7 beta, 12 alpha- and 7 beta,12 beta-dihydroxy-5 beta-cholan-24-oic acids were chemically synthesized with cholic acid (1) as the first starting material. The gas chromatographic retention time of 7 beta,12 beta-dihydroxy-5 beta-cholan-24-oic acid (beta beta-isomer) was more different from that of natural bile acids than the other isomers. Moreover, beta beta-isomer was extracted in the same fraction as the bile acids from urine, and no urinary substance had the same retention time as beta beta-isomer. No artifact was produced from beta beta-isomer during the analysis procedure. It was concluded that the beta beta-isomer is an internal standard compound with certain advantages for the quantitative determination of bile acids in urine by gas chromatography, irrespective of the recovery rate during the analysis procedure.