It is used as a fragrance andfixative in manyperfumes and as anaroma compound. It is also used in low concentrations in some ice cream as a flavor enhancer.[2] Its name derives from the Greek rootskato-, meaning feces. Skatole was discovered in 1877 by the German physicianLudwig Brieger (1849–1919).[3][4][5]
Ich habe mich zuerst mit der Untersuchung der flüchtigen Bestandtheile der Excremente aus sauerer Lösung beschäftigt. Es wurden dabei die flüchtigen Fettsäuren: Essigsäure, normale und Isobuttersäure, sowie die aromatischen Substanzen: Phenol, Indol und eine neue dem Indol verwandte Substanz, die ich Skatol nennen werde, erhalten.
[I was occupied initially with the investigation of the volatile components of excrement in acidic solution. One obtained thereby volatile fatty acids: acetic acid; normal and isobutyric acid; as well as the aromatic substances: phenol, indole and a new indole-derived substance which I will name "skatole".]
Skatole is derived from the amino acidtryptophan in the digestive tract of mammals. Tryptophan is converted toindoleacetic acid, whichdecarboxylates to give the methylindole.[6][7] Once it is created in the digestive tract of mammals, it is metabolized by cytochrome P450 enzymes in the liver.[8]
Skatole, along with the fecal odorantindole, can be neutralized by combining it with other scents, by producing perfumes or air fresheners that lack skatole and indole. In a manner similar tonoise-cancelling headphones, the scent produced by the resultant concentrations of skatole and indole relative to other substances in the freshener is thus "in-phase" and perceived as pleasant.[10]
Skatole is one of many compounds that are attractive to males of various species oforchid bees, which apparently gather the chemical to synthesize pheromones; it is commonly used as bait for these bees for study.[11] It is also known for being an attractant for the Tasmanian grass grub beetle (Aphodius tasmaniae).[12]
Skatole has been shown to be an attractant togravidmosquitoes in both field and laboratory conditions. Because this compound is present in feces, it is found incombined sewage overflows (CSO), as streams and lakes containing CSO water have untreated human and industrial waste. CSO sites are thus of particular interest when studyingmosquito-borne diseases such asWest Nile virus.[13]
The release of skatole by certain parasitic wasps in the familyBethylidae is used to determine which subfamily the species belongs to. Species of the Epyrinae subfamily release skatole, while those in the Bethylinae subfamily release a different chemical, spiroacetal.[14]
Skatole occurs naturally in the feces of all species of mammals and birds, and in thebovinerumen.[15]
Skatole has been shown to causepulmonary edema in goats, sheep, rats, and some strains of mice. It appears to selectively targetclub cells, which are the major site ofcytochrome P450 enzymes in the lungs. These enzymes convert skatole to a reactive intermediate, 3-methyleneindolenine, which damages cells by forming proteinadducts (seefog fever).[16]
With the testicular steroidandrostenone, skatole is regarded as a principal determinant ofboar taint.[17] High amounts of skatole stored in the fat tissue of pigs corresponds with boar taint. To address this, vaccinations with an immunogenic amount ofLawsonia intracellularis antigen are being studied. This antigen reduces the uptake of skatole into the fat of pigs, thus reducing the effect of boar taint.[18] Another method used to address skatole concentration in fat tissue is supplementing the pig's diet with 3% chestnut wood extract. This method showed that intestinal skatole concentration decreased by more than 50%.[8]
^Brieger, Ludwig (1879)."Über Skatol" [On skatole].Berichte der Deutschen Chemischen Gesellschaft.12 (2):1985–1988.doi:10.1002/cber.187901202206. Retrieved3 November 2020.
^Emil Fischer (1886)"Indole aus Phenylhydrazin" (Indole from phenylhydrazine),Annalen der Chemie, vol. 236, pages 126-151; for Fischer's synthesis of skatole, see page 137. (Fischer was not the first to prepare skatole. It was prepared, via other methods, in 1880 by von Baeyer, and in 1883 by Otto Fischer and German and by Fileti.)
^MARLÈNE GOUBAULT, TIM P. BATCHELOR, ROBERTO ROMANI, ROBERT S. T. LINFORTH, MATTHIAS FRITZSCHE, WITTKO FRANCKE, IAN C. W. HARDY, Volatile chemical release by bethylid wasps: identity, phylogeny, anatomy and behaviour,Biological Journal of the Linnean Society, Volume 94, Issue 4, August 2008, Pages 837–852, https://doi.org/10.1111/j.1095-8312.2008.01022.x
