Chapter 10 Bile alcohols and primitive bile acids

Abstract

Publisher Summary The bile acids in bile of mammals are taurine and glycine conjugates of derivatives of cholanoic acid. The bile of evolutionarily more primitive vertebrates contain other types of bile salts, that is, sulfuric acid esters of bile alcohols and taurine-conjugated or unconjugated bile acids with more than 24 carbon atoms (higher bile acids). Although both types of compounds have the bile acid type of nuclear structure, they are chemically closer to cholesterol than the common bile acids. Until recently, bile alcohols and higher bile acids were supposed to occur only in the primitive vertebrates. However, it is now realized that they are present in mammals, including healthy and diseased humans. In addition, C24 bile acids having a 3β-hydroxyl group and a double bond at position 5 have been found in humans. In this chapter, these cholenoic acid derivatives as well as higher bile acids are defined as primitive bile acids. The occurrence in nature of bile alcohols and primitive bile acids is especially interesting as these compounds appear to represent not only evolutionary precursors but also biosynthetic intermediates in the formation of the common C24 bile acids. The chapter reviews the natural distribution, the chemical structure, and the metabolism of bile alcohols and primitive bile acids.