Journal of Lipid Research, Vol. 9, 707-713, November 1968
Copyright © 1968 by Lipid Research, Inc.

Rapid preparation of tritium-labeled bile acids by enolic exchange on basic alumina containing tritiated water

Alan F. Hofmann , Patricia A. Szczepanik , and Peter D. Klein

Gastroenterology Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901; and the Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Illinois 60439

When a 3-keto bile acid methyl ester was chromatographed on basic alumina inactivated with tritiated water, the enolic hydrogen atoms at C-2 and C-4 exchanged with tritium atoms. The ³H-labeled keto ester was reduced with borohydride, and the resultant mixture of 3- and 3ßbeta;-hydroxy epimers was resolved by preparative thin-layer chromatography to yield a pure 2,4-³H-labeled bile acid ester. Lithocholic, chenodeoxycholic, deoxycholic, and cholic acids having a specific activity of 1-10 µc/µmole were prepared from their 3-keto derivatives. The tritium label remained intact during alkaline saponification in vitro and enterohepatic cycling in vivo in human subjects.

Supplementary key words exchange labeling • bile acid epimers • thin-layer chromatography • isotope fractionation

Submitted on May 15, 1968
Accepted on July 22, 1968

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