Microbial transformation of bile acids. A unified scheme for bile acid degradation, and hydroxylation of bile acids.

Through the isolation and identification of a wide variety of degradation products formed from bile acids by microorganisms, a unified scheme for the complete degradation of bile acids to carbon dioxide and water has been proposed and discussed. The proposed degradative pathways mainly consist of the following steps: natural C24 3-hydroxy bile acids leads to 3-oxo bile acids leads to delta 4-3-oxo bile acids leads to C16 or C18 perhydroindane derivative (at least in two ways) leads to (4 epsilon)-4-methyl-5-oxo-octanedioic acid (at least in three ways) leads to CO2 and H2O. A microbial hydroxylation method for the preparation of bile acid samples was investigated which could be used as reference standards in the analysis of bile acids in biological materials and also as materials for studying the function of bile acids. The particular fungi, Curcularia lunata NRRL-2380, Helicostylum piriforme ATTC-8992 and Pestalotia foedans ATCC-11817 effected the 1 beta-, 11 beta-, 12 beta-, 15 alpha- or 15 beta-hydroxylation of certain bile acids and gave the following products: 1 beta, 3 alpha-, 3 alpha, 12 beta- and 3 alpha, 15 beta-dihydroxy-5 beta-cholan-24-oic acids, 3 alpha, 12 beta, 15 alpha- and 3 alpha, 12 beta, 15 beta-trihydroxy-5 beta-cholan-24-oic acids and 12 beta, 15 beta-dihydroxy-3-oxo-5 beta-cholan-24-oic acids from lithocholic acid; 1 beta, 3 alpha, 12 alpha- and 3 alpha, 12 alpha, 15 beta-trihydroxy-5 beta-cholan-24-oic acids and 3 alpha, 11 beta-dihydroxy-12-oxo-5 beta-cholan-24-oic acid from deoxycholic acid; 3 alpha, 7 alpha, 12 beta-trihydroxy-5 beta-cholan-24-oic acid and 3 alpha, 7 alpha, 12 beta, 15 alpha-tetrahydroxy-5 beta-cholan-24-oic acid from chenodeoxycholic acid; 3 alpha-6 alpha, 12 beta- and 3 alpha, 6 alpha, 15 beta-trihydroxy-5 beta-cholan-24-oic acids from hyodeoxycholic acid; 3 alpha, 7 beta, 12 beta trihydroxy-5 beta-cholan-24-oic acid from ursodeoxycholic acid; 3 alpha, 12 beta-dihydroxy-7-oxo-5 beta-cholan-24-oic acid from 3 alpha-hydroxy-7-oxo-5 beta-cholan-24-oic acid. Some of these products were new compounds and their structures were determined.