Synthesis of Primary Bile Acids

The synthesis of cholic acid from cholesterol in rodents proceeds via 7a-OH-cholesterol, leading to a trihydroxy derivative which finally loses a side chain, resulting in the formation of cholic acid (1). The synthesis appears to proceed similarly in the human liver (12). Trihydroxycoprostanic acid, which is a precursor of cholic acid and which is formed from cholesterol 

It seems quite apparent that 7a-OH-cholesterol serves as a primary intermediate in human chenodeoxycholic acid synthesis (1). 5 -cholestane-3a,7a-diol and, further, dihydroxycoprostanic acid have been found in human bile (17). The latter is known to be converted finally to chenodeoxy-cholate (18). Thus dihydroxycoprostanic acid belongs to the primary human bile acids. 

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Figure 6.2 Synthesis of primary bile acids from cholesterol. 

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