June 07, 2021
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Urobilin, also known as urochrome, is a tetrapyrroledicarboxylic acid that causes the yellow color in urine. The natural compound has the (–) stereochemical configuration.

In the 1930s, hepatologist Cecil James Watson at the University of Minnesota Hospitals (Minneapolis) published a pioneering series of articles on urobilin and its derivatives. In one (1935), he reported differences in properties among various urobilin analogues.

Watson also studied stercobilin (CAS Registry no. 34217-90-8), a similarly structured molecule that is responsible for the color of feces. The two are similar to bilirubin, the Molecule of the Week for March 27, 2017. All three are bile pigments formed in the liver and spleen as breakdown products from hemoglobin-derived porphyrins.

Urobilin is a key marker in urinalysis. For example, if a patient’s urine has a deep yellow color, it may indicate that the patient is dehydrated. If you’re a parent, and your child asks why urine is yellow, an entry in The Conversation will help you provide a suitable answer.

Urobilin hazard information*

Hazard class**Hazard statement

Not a hazardous substance or mixture


*No urobilin safety data sheet is available. Information is for the chemically similar urobilin hydrochloride.
**Globally Harmonized System of Classification and Labeling of Chemicals.  

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fast facts

CAS Reg. No.1856-98-0
21H-Biline-8,12-dipropanoic acid, 3,18-diethyl-1,4,5,15,16,19,22,24-octahydro-2,7,13,17-tetramethyl-1,19-dioxo-
Empirical formulaC33H42N4O6
Molar mass590.71 g/mol
AppearanceYellow crystals
Melting point236 ºCa
Water solubilitySoluble
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