Skatole

Skatole is derived from the amino acid tryptophan in the digestive tract of mammals. Tryptophan is converted to indoleacetic acid, which decarboxylates to give the methylindole. Once it is created in the digestive tract of mammals, it is metabolized by cytochrome P450 enzymes in the liver. Skatole can be prepared in the laboratory via the Fischer indole synthesis, a method for the formation of indole derivatives from phenylhydrazines and carbonyl compounds. Phenylhydrazine and propanal can be used. A simplified reaction scheme is shown below. : It gives a violet color upon treatment with potassium ferrocyanide. ==Insect studies==

Skatole is one of many compounds that are attractive to males of various species of orchid bees, which apparently gather the chemical to synthesize pheromones; it is commonly used as bait for these bees for study. It is also known for being an attractant for the Tasmanian grass grub beetle (Aphodius tasmaniae). Skatole has been shown to be an attractant to gravid mosquitoes in both field and laboratory conditions. Because this compound is present in feces, it is found in combined sewage overflows (CSO), as streams and lakes containing CSO water have untreated human and industrial waste. CSO sites are thus of particular interest when studying mosquito-borne diseases such as West Nile virus. The release of skatole by certain parasitic wasps in the family Bethylidae 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. ==Animal studies==

Skatole occurs naturally in the feces of all species of mammals and birds, and in the bovine rumen. Skatole has been shown to cause pulmonary edema in goats, sheep, rats, and some strains of mice. It appears to selectively target club cells, which are the major site of cytochrome P450 enzymes in the lungs. These enzymes convert skatole to a reactive intermediate, 3-methyleneindolenine, which damages cells by forming protein adducts (see fog fever). High amounts of skatole stored in the fat tissue of pigs corresponds with boar taint. To address this, vaccinations with an immunogenic amount of Lawsonia intracellularis antigen are being studied. This antigen reduces the uptake of skatole into the fat of pigs, thus reducing the effect of boar taint. 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%. ==Applications==

Skatole is the starting material used in the synthesis of: • Atiprosin • Nerispirdine (besipirdine analog). • 3-Methyl-3-piperidinooxindole [55490-24-9] (see page 751): ==See also==