An acid found in bile (secretion of the liver). Bile acids are steroids having a hydroxyl group and a five-carbon-atom side chain terminating in a carboxyl group. Cholic acid is the most abundant bile acid in human bile. Others are deoxycholic and lithocholic acids. The bile acids do not occur free in bile but are linked to the amino acids glycine and taurine. These conjugated acids are water soluble. Their salts are powerful detergents and as such aid in the absorption of fats from the intestine.
There are three main routes for the preparation of bile acids: extraction from natural sources, chemical synthesis, and biotransformation. Historically, bile acids were extracted from animal bile, but this method is time-consuming and labor-intensive, and yields a mixture of various compounds. Chemical synthesis typically uses readily available steroidal compounds (such as cholesterol or bile acids) as starting materials to produce specific, pure bile acids, including rare or modified forms, but usually requires complex multi-step organic reactions. In recent years, biotransformation using microorganisms has become a highly efficient and environmentally friendly method. This method utilizes bacteria or fungi to selectively modify the core structure of steroids, converting precursor steroidal compounds into desired bile acids, such as ursodeoxycholic acid (UDCA).
