Skatole



This molecule's name comes from 'skatalogical', meaning concerning fecal material. Its proper name is 3-methylindole, but it gets its trivial name from the fact that it is a component of feces. Surprisingly, it is also found in coal tar and beetroot, and can be obtained synthetically by mixing egg albumin and KOH. Skatole consists of white crystals when pure (or brownish scales when impure) which are soluble in hot water. It has a floral aroma at low concentrations, contributing to the pleasant aroma of flowers such as jasmine and orange blossom. Skatole also naturally occurs in substances such as beetroot and coal tar.

Chemical properties
Skatole can be found as a white crystalline or fine powder solid, and it browns upon aging. It is nitrogenous, and one of the rings is a pyrrole. It is soluble in alcohol and benzene, and it gives a violet color in potassium ferrocyanide (K4Fe(CN)6·3H2O) and sulfuric acid (H2SO4). Skatole has a double ring system that displays aromaticity. It is continuous (all atoms in the ring are sp² hybridized), planar, and follows the 4n+2 rule because it has 10 π electrons. It can be synthesized through a Fischer indole synthesis, which was developed by Emil Fischer.

Insect attractant
Skatole is one of many compounds that is attractive to males of various species of orchid bees, who apparently gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study. 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. Knowledge of this attractant makes CSO sites of particular interest when studying mosquito-borne diseases such as West Nile Virus

Safety
Skatole has been shown to cause pulmonary edema in goats, sheep, rats, and some strains of mice. It appears to selectively target Clara 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.