Glycoursodeoxycholic acid-d₄(GUDCA-d₄) is intended for use as an internal standard for the quantification of GUDCA by GC- or LC-MS. GUDCA is a glycine-conjugated form of the secondary bile acid ursodeoxycholic acid .^1,2It has antioxidant effectsin vitroin Barrett's esophagus cells and primary cultured rat neurons.^3,4GUDCA reduces the levels of inflammatory cytokines and prevents cell death induced by unconjugated bilirubin in an astroglial cell model of neonatal hyperbilirubinemia.⁵Oral administration of GUDCA (500 mg/kg per day) decreases the severity of symptoms and increases the amount ofA. muciniphila, a commensal bacterial species commonly decreased in patients with inflammatory bowel disease (IBD), in a mouse model of colitis.²

1.Lefebvre, P., Cariou, B., Lien, F., et al.Role of bile acids and bile acid receptors in metabolic regulationPhysiol. Rev.89(1)147-191(2009) 2.Van den Bossche, L., Hindryckx, P., Devisscher, L., et al.Ursodeoxycholic acid and its taurine- or glycine-conjugated species reduce colitogenic dysbiosis and equally suppress experimental colitis in miceAppl. Environ. Microbiol.83(7)e02766-02716(2017) 3.Goldman, A., Condon, A., Adler, E., et al.Protective effects of glycoursodeoxycholic acid in Barrett's esophagus cellsDis. Esophagus23(2)83-93(2010) 4.Brito, M.A., Lima, S., Fernandes, A., et al.Bilirubin injury to neurons: Contribution of oxidative stress and rescue by glycoursodeoxycholic acidNeurotoxicology29(2)259-269(2008) 5.Fernandes, A., Vaz, A.R., Falcao, A.S., et al.Glycoursodeoxycholic acid and interleukin-10 modulate the reactivity of rat cortical astrocytes to unconjugated bilirubinJ. Neuropathol. Exp. Neurol.66(9)789-798(2007)