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CAS number 1856-98-0 N
PubChem 6433298
ChemSpider 4938471 YesY
MeSH Urobilin
Jmol-3D images Image 1
Molecular formula C33H42N4O6
Molar mass 590.71
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Urobilin or urochrome is the chemical primarily responsible for the yellow color of urine. It is a linear tetrapyrrole compound that, along with the related compound urobilinogen, are degradation products of the cyclic tetrapyrrole heme.


Urobilin is generated from the degradation of heme, which is first degraded through biliverdin to bilirubin. Bilirubin is then excreted as bile, which is further degraded by microbes present in the large intestine to urobilinogen, and reabsorbed into the bloodstream, where it is oxidized to urobilin and eventually excreted by the kidneys.[1]


Many urine tests (urinalysis) monitor the amount of urobilin in urine, as its levels can give insight on the effectiveness of urinary tract function. Normally, urine would appear as either light yellow urine or colorless. A lack of water intake, for example following sleep or dehydration, reduces the water content of urine, thereby concentrating urobilin and producing a darker color of urine. Obstructive jaundice reduces biliary bilirubin excretion, which is then excreted directly from the blood stream into the urine, giving a dark-colored urine but with a paradoxically low urobilin concentration, no urobilinogen, and usually with correspondingly pale faeces. Darker urine also results due to other chemicals, such as various ingested dietary components or drugs, porphyrins in porphyria, and homogentisate in patients with alcaptonuria.

See also[edit]


  1. ^ Donald J. Voet; Judith G. Voet; Charlotte W. Pratt (2008). "Synthesis and degradation of amino acids". Principles of Biochemistry, Third edition. Wiley. p. 778. ISBN 978-0470-23396-2. 
  1. Voet and Voet Biochemistry Ed 3 page 1022
  2. Nelson, L., David, Cox M.M., .2005. “Chapter 22- Biosynthesis of Amino Acids, Nucleotides, and Related Molecules”, pp. 856, In Lehninger Principles of Biochemistry. Freeman, New York. pp. 856
  3. Bishop, Michael, Duben-Engelkirk, Janet L., and Fody, Edward P. "Chapter 19, Liver Function, Clinical Chemistry Principles, Procedures, Correlations, 2nd Ed." Philadelphia: copyright 1992 J.B. Lippincott Company.
  4. Munson-Ringsrud, Karen and Jorgenson-Linné, Jean "Urinalysis and Body Fluids, A ColorText and Atlas." St. Louis: copyright 1995 Mosby