Bilirubin (unconjugated)

Bilirubin is a yellow bile pigment derived from heme degradation, commonly used as a biochemical marker for liver function and oxidative stress. It exhibits significant antioxidant properties and plays crucial roles in various physiological and pathological processes. Research applications span liver disease, neonatology, enzymology, and emerging therapeutic fields.

• Formula: C₃₃H₃₆N₄O₆
• Molecular weight: 584.66

• Bilirubin is a heme metabolism byproduct and a biomarker of liver function and heme metabolism. When red blood cells are broken down in the spleen and liver, heme is converted into biliverdin, which is then reduced to unconjugated bilirubin.
• Bilirubin acts as a potent endogenous antioxidant, helping to neutralize harmful reactive oxygen species (ROS) and protest cells from oxidative damage.
• Bilirubin serves as a substrate or product in enzymatic studies (e.g. heme oxygenase, biliverdin reductase).

• Antioxidant mechanism: Bilirubin scavenges peroxyl radicals and inhibits lipid peroxidation, acting through a redox cycle with biliverdin.
• Unconjugated (indirect) form of bilirubin is lipid-soluble and binds to albumin in the bloodstream for transport to the liver. In the liver, it is conjugated with glucuronic acid to form conjugated (direct) bilirubin, making it water-soluble for excretion in bile, via ABCC2/MRP2, an ATP-dependent transporter.

• Liver disease studies: As a diagnostic marker in jaundice, hepatitis, cirrhosis, and bile duct obstruction.
• Neonatal medicine: Used in research on neonatal hyperbilirubinemia and kernicterus.
• Enzyme kinetics: Used to study enzymes like UDP-glucuronosyltransferases and biliverdin reductase.
• Oxidative stress and inflammation: Used to study its antioxidant properties in conditions like atherosclerosis, diabetes, neurodegeneration, and ischemia-reperfusion injury.
• Pharmacological studies: Investigating bilirubin’s potential therapeutic effects in modulating immune response, cancer biology, and cell signaling pathways (e.g., Nrf2 pathway).
• Phototherapy research: As a model compound in light-induced isomerization studies (used in phototherapy of neonatal jaundice).

• Sources: purified from porcine bile
• Available as reddish orange powder
• Store in a dry and cool place, protected from light