Glycoursodeoxycholic Acid-d4 is a deuterated compound of Glycoursodeoxycholic Acid. Glycoursodeoxycholic Acid has a CAS number of 64480-66-6. Glycoursodeoxycholic acid is an acyl glycine and a bile acid-glycine conjugate. It is a secondary bile acid produced by the action of enzymes existing in the microbial flora of the colonic environment. In hepatocytes, both primary and secondary bile acids undergo amino acid conjugation at the C-24 carboxylic acid on the side chain, and almost all bile acids in the bile duct, therefore, exist in a glycine conjugated form. Bile acids are steroid acids found predominantly in bile of mammals.