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 → 3-oxo bile acids → Δ⁴-3-oxo bile acids → → C₁₆ or C₁₈ perhydroindane derivative (at least in two ways) → → (4→)-4-methyl-5-oxo-octanedioic acid (at least in three ways) → → 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 1β-, 11β-, 12β-, 15α- or 15β-hydroxylation of certain bile acids and gave the following products: 1β,3α-, 3α,12β- and 3α,15β-dihydroxy-5β-cholan ?24-oic acids, 3α,12β,15α- and 3α,12β, 15β-trihydroxy-5β-cholan-24-oic acids and 12β,15β-dihydroxy-3-oxo-5β-cholan-24-oic acid from-lithocholic acid; 1β,3α,12α- and 3α,12α,15β-trihydroxy-5β-cholan-24-oic acids and 3α, 11β-dihydroxy-12-oxo-5β-cholan-24-oic acid from deoxycholic acid; 3α, 7α, 12β-trihydroxy-5β-cholan-24-oic acid 3α,7α,12β, 15α-tetrahydroxy-5β-cholan-24-oic acid from chenodeoxycholic acid; 3α-6α,12β- and 3α,6α, 15β-trihydroxy-5β-cholan-24-oic acids from hyodeoxycholic acid; 3α, 7β, 12β trihydroxy-5β-cholan-24-oic acid from ursodeoxycholic acid; 3α,12β-dihydroxy-7-oxo-5β-cholan-24-oic acid from 3α-hydroxy-7-oxo-5β-cholan-24-oic acid. Some of these products were new compounds and their structures were determine.