Physicochemical and biological properties of natural and synthetic C-22 and C-23 hydroxylated bile acids

A. Roda, B. Grigolo, A. Minutello, R. Pellicciari, B. Natalini

Research output: Contribution to journalArticle


In order to define the effect of a side chain hydroxy group on bile acid (BA) physicochemical and biological properties, 23-hydroxylated bile acids were synthesized following a new efficient route involving the α-oxygenation of silylalkenes. 22-Hydroxylated bile acids were also studied. The synthesized bile acids included R and S epimers of 3α,7α,23-trihydroxy-5β-cholan-24-oic acid (23R epimer: phocaecholic acid), 3α,12α,23-trihydroxy-5β-cholan-24-oic (23R epimer: bitocholic acid), and 3α,7β,23-trihydroxy-5β-cholan-24-oic acid. A 3α,7α,22-trihydroxy-5β-cholan-24-oic acid (haemulcholic acid) was also studied. The presence of a hydroxy group on the side chain slightly modified the physicochemical behavior in aqueous solution with respect to common BA: the critical micellar concentration (CMC) and the hydrophobicity were similar to naturally occurring trihydroxy BA such as cholic acid. The pKa value was lowered by 1.5 units with respect to common BA, being 3.8 for all the C-23 hydroxy BA. C-22 had a higher pKa (4.2) as a result of the increased distance of the hydroxy group from the carboxy group. When the C-23 hydroxylated BA were intravenously administered to bile fistula rats, they were efficiently recovered in bile (more than 80% unmodified) while the corresponding analogs, lacking the 23-hydroxy group, were almost completely glycine- or taurine-conjugated. On the other hand, the C-22 hydroxylated BA were extensively conjugated with taurine and less than 40% of the administered dose was secreted without being conjugated. In the presence of intestinal bacteria, they were mostly metabolized to the corresponding 7-dehydroxylated compound similar to common BA with the exception of bitocholic acid which was relatively stable. The presence of a hydroxy group at the C-23 position increased the acidity of the BA and this accounted for poor absorption within the biliary tree and efficient biliary secretion without the need for conjugation. 3α,7β-23 R/S trihydroxy-5β-cholan-24-oic acids could improve the efficiency of ursodeoxycholic acid (UDCA) for gallstone dissolution or cholestatic syndrome therapy, as it is relatively hydrophilic and efficiently secreted into bile without altering the glycine and taurine hepatic pool.

Original languageEnglish
Pages (from-to)289-298
Number of pages10
JournalJournal of Lipid Research
Issue number2
Publication statusPublished - 1990


  • Activity relationship
  • Bile acid analogs
  • Bile acid structure
  • Cholesterol gallstones

ASJC Scopus subject areas

  • Endocrinology

Fingerprint Dive into the research topics of 'Physicochemical and biological properties of natural and synthetic C-22 and C-23 hydroxylated bile acids'. Together they form a unique fingerprint.

  • Cite this