What molecule am I?
Stercobilin is a bile pigment related to former Molecule of the Week urobilin1. Whereas urobilin causes the yellow color of urine, stercobilin is responsible for the brown color of feces. Both molecules are optically active; the natural forms present in the (–) configuration.
An early report of stercobilin in the scientific literature appeared in 1908, when Augustin Gilbert* and M. Herscher at Hôtel-Dieu de Paris (a hospital) described its appearance in normal feces. The most prolific researcher into stercobilin was physician C. J. Watson at Northwestern Hospital (Minneapolis); in 1971, he and collaborators in Minneapolis and West Germany determined the absolute configuration of (–)-stercobilin and other urobilinoid molecules.
Because fecal matter is a primary source of water pollution, the quantification of stercobilin and other fecal pigments (FPs) in aqueous media is important. In 2020, Swayam Prakash and Ashok Kumar Mishra* at IIT Madras (Chennai, India) described the detection of stercobilin and urobilin monomers, dimers, and higher order hydrogen-bonded aggregates using steady-state absorbance, fluorescence, and time-resolved fluorescence decay techniques. The authors varied FP concentration, temperature, pH, and ethanol–water composition to obtain extensive data on the FP species present under the range of conditions studied.
1. CAS Reg. No. 1856-98-0.
Stercobilin hazard information
| Hazard class* | GHS code and hazard statement | |
|---|---|---|
| Acute toxicity, oral, category 4 | H302—Harmful if swallowed |  |
| Skin corrosion/irritation, category 2 | H315—Causes skin irritation | |
| Serious eye damage/eye irritation, category 2A | H319—Causes serious eye irritation | |
| Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335—May cause respiratory irritation | |
*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.
Molecules from the Journals
Asperjinone1, a nor-neolignan natural product with a maleic anhydride core, was isolated in 2012 from the marine fungus Aspergillus terreus by Chih-Chuang Liaw at National Sun Yat-sen University (Kaohsiung, Taiwan) and coauthors at other Taiwanese institutions. Liaw et al. also isolated the cyclopentenone terrein2, a robust growth suppressor of breast cancer cells expressed by the ABCG2 gene.
The following year, Antony J. Williams at the Royal Society of Chemistry (Wake Forest, NC, facility) and collaborators in Russia reported a revised structure of asperjinone from that given by the Liaw group. They used Structure Elucidator to determine the revision.
This past August, Kwanruthai Tadpetch at Prince of Songkla University (Songkla, Thailand) and colleagues at other Thai institutions reported the total synthesis of the racemic and chiral forms of asperjinone and a similar compound, asperimide C3. Asperjinone also exhibited significant anti-inflammatory activity in renal proximal tubular epithelial cells by suppressing the gene expression of pro-inflammatory cytokines TNF-α, IL-1β, and IL-6. The authors anticipate that this discovery could lead to developing agents to combat inflammation-worsening acute kidney injury.
Terebic acid4 is a lactone carboxylic acid that was identified in 1893 by S. B. Schryver at University College, Liverpool (UK) as one of the main oxidation products of turpentine. Later studies showed that it is generated via the natural degradation of monoterpenes such as α-pinene5, β-pinene6, and Δ3-carene7.
In 1960, Gunther O. Schenck* and Reinhard Steinmetz at the Max Planck Institute for Coal Research (Mülheim an der Ruhr, West Germany) reported the synthesis of terebic acid via the benzophenone-sensitized UV irradiation of maleic or fumaric anhydride with benzene.
Terebic acid has been identified in aerosol samples taken from terrestrial and forest environments. This month, Spyros N. Pandis at the Institute of Chemical Engineering Sciences (Patras, Greece) and the University of Patras and collaborators there and in Poland and the United States described the properties and atmospheric oxidation of terebic acid aerosol. The authors found that the aerosol density is 1.3 g/cm3, and its vaporization enthalpy is 85 kJ/mol. Oxidation of the aerosol by hydroxyl radicals reduced the mass by up to 80%; the oxidation products were smaller molecules such as acetone.
1. CAS Reg. No. 1361320-14-0.
2. CAS Reg. No. 582-46-7.
3. No CAS Reg. No. assigned.
4. CAS Reg. No. 79-91-4.
5. CAS Reg. No. 80-56-8.
6. CAS Reg. No. 127-91-3.
7. CAS Reg. No. 13466-78-9.
Molecules from the Journals
MOTW briefly describes noteworthy molecules that appeared in recent ACS journal articles. See this week's
edition.
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Stercobilin
fast facts
| CAS Reg. No. | 34217-90-8 |
| SciFindern name | (–)-Stercobilina |
| Empirical formula | C33H46N4O6 |
| Molar mass | 594.74 g/mol |
| Appearance | Brown crystals |
| Melting point | 236 °C |
| Water solubility | Slightb |
a. Full name: 21H-biline-8,12-dipropanoic acid, 3,18-diethyl-1,2,3,4,5,15,16,17,18,19,22,24-dodecahydro-2,7,13,17-tetramethyl-1,19-dioxo-, (2R,3R,4S,16S,17R,18R)-.
b. The hydrochloride is soluble in aqueous media with pH > 9.
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