Stercobilin
IUPAC name	3-[(2E)-2-[ [3-(2-Carboxyethyl)-5- [(4-ethyl-3-methyl-5-oxo-pyrrolidin-2-yl) methyl]-4-methyl-1H-pyrrol-2-yl]methylidene]-5- [(3-ethyl-4-methyl-5-oxo-pyrrolidin-2-yl) methyl]-4-methyl-pyrrol-3-yl]propanoic acid
Identifiers
CAS number	34217-90-8
PubChem	5280818
MeSH	Stercobilin
Properties
Molecular formula	C33H46N4O6
Molar mass	594.742
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Stercobilin is a tetrapyrrolic bile pigment and is one end product of heme catabolism ^[1][2]. It is the chemical responsible for the brown color of human fecal material ^[1] and was originally isolated from feces in 1932 ^[2]. Stercobilin (and related urobilin) can be used as a marker for biochemical identification of fecal pollution levels in rivers ^[3].

[edit] Metabolism

Stercobilin results from breakdown of the heme moiety of hemoglobin found in erythrocytes ^[2]. Macrophages break down senescent erythrocytes and break the heme down into biliverdin, which rapidly reduces to free bilirubin ^[1]. Bilirubin binds tightly to plasma proteins (especially albumin) in the blood stream and is transported to the liver, where it is conjugated with one or two glucoronic acid residues into bilirubin glucoronide, and secreted into the small intestine as bile ^[4]. In the small intestine, some bilirubin glucoronide is converted back to bilirubin via bacterial enzymes in the terminal ileum ^[1]. This bilirubin is further converted to colorless urobilinogen ^[1]. Any urobilinogen that remains in the colon is converted to stercobilinogen and finally oxidized to stercobilin, which is responsible for the brown color of human feces ^[1]. Stercobilin is then excreted in the feces ^[4].

[edit] Role in disease

Obstructive jaundice

In obstructive jaundice, no bilirubin reaches the small intestine, meaning that there is no formation of urobilinogen. As a result, no stercobilin is formed. This lack of stercobilin and other bile pigments causes feces to become clay-colored ^[1].

Brown pigment gallstones

An analysis of two infants suffering from cholelithiasis observed that a substantial amount of stercobilin was present in brown pigment gallstones. This study suggested that brown pigment gallstones could form spontaneously in infants suffering from bacterial infections of the biliary tract ^[5].

[edit] Role in treatment of disease

A 1996 study by McPhee et al. suggested that stercobilin and other related pyrrolic pigments—including urobilin, biliverdin, dimethyl ester, and xanthobilirubic acid—may potentially function as a new class of HIV-1 protease inhibitors when delivered at low micromolar concentrations. These pigments were selected due to a similar in shape to the successful HIV-1 protease inhibitor Merck L-700,417. Further research is suggested to study the pharmacological efficacy of these pigments ^[6].

[edit] See also

• Bile pigment
• Bilirubin
• Biliverdin
• Heme
• Tetrapyrrole
• Urobilin

[edit] External links

http://www.chem.qmul.ac.uk/iupac/tetrapyrrole/TP/D6.html

[edit] References

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