Quantitative determination of bile acid glucuronides in serum by mass fragmentography

Individual non-glucuronidated . non-sulfated, glucuronidated and sulfated bile acids in serum were determined, i.e. lithocholic acid, deoxycholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and cholic acid, by mass fragmentography. Glucuronic acid conjugates of lithocholic acid, deoxycholic acid, chenodeoxycholic acid, and cholic acid were synthesized via the Koenigs-Knorr condensation reaction. Deuterium labeled deoxycholic acid, lithocholic acid glucuronide, deoxycholic acid glucuronide, and deoxycholic acid sulfate were synthesized and used as internal standards. A serum sample of 1 ml including internal standards was purified with a Sep-Pak C18 cartridge. After the enzymatic cleavage of amino acid conjugates, bile acids were separated into three fractions, free, glucuronidated, and sulfated bile acids, using piperidinohydroxypropyl Sephadex LH-20 (Goto et al. (1978) Clin. Chim. Acta 87). Glucuronidated and sulfated bile acids were deconjugated by beta-glucuronidase treatment and solvolysis. Each fraction was converted to the hexafluoroisopropyl-trifluoroacetyl derivative and quantitated by mass fragmentography. The average concentrations of individual bile acid glucuronides from healthy fasting subjects (n = 9) were as follows; lithocholic acid 0.013 microgram/ml, deoxycholic acid 0.083 microgram/ml, chenodeoxycholic acid 0.078 microgram/ml, ursodeoxycholic acid 0.013 microgram/ml, and cholic acid 0.007 microgram/ml. Bile acid glucuronides occupied 7.8% of the total bile acids.