Bile acids, primitive, mammals

V) Occurrence and structure of primitive bile acids in mammals... 

Primitive bile acids in mammals may be classified by carbon numbers as higher bile acids and as cholenoic acid derivatives. A list of primitive bile acids from mammalian sources is given in Table 4. 

The natural distribution and the chemical structure of bile alcohols and primitive bile acids indicate that these compounds found in lower vertebrates are evolutionary precursors of the common bile acids found in mammalian species. Haslewood proposed that the mechanism of conversion of cholesterol to the common bile acids in mammals is a recapitulation of the evolution of bile salts and thus would entail the intermediary formation of bile alcohols and primitive bile adds similar to or the same as those found in lower species [120]. Thus, studies have been carried out to test whether the naturally occurring bile alcohols and primitive bile acids are intermediates in the biosynthetic pathway between cholesterol and the C24 bile acids in mammals. There is no doubt that such studies contributed to the elucidation of the sequence of reactions in the biosynthesis of the mammalian C24 bile acids. 

Studies on the biosynthesis of bile alcohols and primitive bile acids in lower vertebrates will provide additional information on the formation of the common bile acids in mammals and will help to clarify the molecular evolution of bile salts. However, such studies have been carried out only in a few species of lower vertebrates. 

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