Skatole or 3-methylindole is a mildly toxic white crystalline organic compound belonging to the indole family. It is formed in the intestine by the bacterial decomposition of l-tryptophan and found in fecal matter, to which it imparts its characteristic odor. Skatole is a partial AhR agonist. Skatole is used in perfume compositions and in artificial Civet bases.

Diethyl sulfide, a food flavor ingredient, possesses garlic-like odor. It is used as a solvent and to make other chemicals. Diethyl sulfide can irritate the skin and eyes, breathing of this compound can irritate the nose and throat.

p-tert-butylphenol is in public use since the 1930s. It is used as an intermediate in the manufacture of varnish and lacquer resin. It has apparently not been reported to occur in nature. There is an abundant literature dealing with the well-established sensitization and depigmentation (vitiligo) properties of p-tert-butylphenol.

Methyl Undecylenate is a linear ester with a terminal double bond, that can be used as a chemical intermediate in the synthesis of aromatic chemicals, of polymers or modified silicones. Methyl undecylenate is produced by fractional distillation of the product obtained by the pyrolysis of methyl ricinoleate at a high temperature. Methyl undecylenate is used as a chemical intermediate in the synthesis of organo-modified silicones for hair care preparations and sun care products. It can also be used as a chemical intermediate for synthesizing derivatives based on ammonium or ethanolamide used in hair-care products.

Furfural (also called 2-formylfuran, furan-2- aldehyde, 2-furancarboxaldehyde, 2-furyl-methanal, pyromucic aldehyde, 2-furanaldehyde, 2-furancarbonal, carboxylic aldehyde, furan-2-carbaldehyde, furancarbonal, 2-furaldehyde, or 2-furfural), contains a heteroaromatic furan ring and an aldehyde functional group. Furfural was first isolated in 1832 by J.W. Döbereiner, and has been industrially produced since 1922. Today, furfural is used for multiple purposes, for example as a selective extraction agent (in the recovery of butadiene from oil steam cracking or in the refining of petroleum, diesel fuels, lubricants and vegetable oils), as a solvent (for anthracene or resins), as an agent for vulcanization, as a nematicide and fungicide, as a flavoring agent in a variety of food products and alcoholic and non-alcoholic beverages, and as a component of commercial herbicides, insecticides, pesticides, antiseptics, disinfectors, and rust removers. Furfural is also involved in the manufacture of pharmaceuticals, cosmetics, fragrances, flavors and resins (in this latter case, by condensation with phenol, formaldehyde, acetone, or urea, to produce thermosetting resins with extreme physical strength); as well as in other products such as household cleaners and detergents. Furfural occurs naturally in some fruits and vegetables. It can be formed in other foods during cooking, and is present in wood smoke. Furfural is an ingredient contained in many fragrances and flavours. It may be found in fragrances used in decorative cosmetics, fine fragrances, shampoos, toilet soaps and other toiletries, in flavours of oral care products as well as in non-cosmetic products such as household cleaners and detergents. Furfural in the in the fragrance compound is reported to be 0.036% or less. The European Commission received a submission from the European Flavour & Fragrance Association with data supporting the safe use of Furfural as a fragrance ingredient. The predominant pathway of metabolism of Furfural in humans is oxidation of the aldehyde to yield furoic acid, which may either conjugate with amino acids or condense with acetyl coenzyme A to produce the furanacrylic acid. Furfural is a carcinogen classified in EU as a Category 3 carcinogen. Furfural was tested for carcinogenicity by oral administration in one study in mice and one study in rats. In mice, it increased the incidence of hepatocellular adenomas and carcinomas in males and of hepatocellular adenomas and forestomach papillomas in females. Male rats had a low incidence of cholangiocarcinomas, which occur rarely. In a two-stage assay on mouse skin, Furfural had weak initiating activity. On the basis of quantitative risk assessment it is concluded that Furfural at the maximum exposure stated by RIFM does not represent any significant cancer risk. However, the exposure should not be increased.

(+)-Fenchone, a bicyclic monoterpene, is widely distributed in plants and found in essential oils from Foeniculum vulgare. This component has camphoraceous fragrance. (+)-Fenchone is used as a food flavour and in perfumes. Although, there are report that (+)-fenchone has toxic. P450 enzymes are shown to detoxify and/or toxify these compounds to metabolites more polar and sometimes more reactive metabolites. (+)-fenchone are oxidized to 6-endo-hydroxyfenchone, 6-exo-hydroxyfenchone and 10-hydroxyfenchone derivatives in human liver microsomes. CYP2A6 is suggested to be a principal enzyme in catalyzing (+)-fenchone 6-exo and 6-endo hydroxylation by human liver microsomes. 10-Hydroxylation of (+)-fenchone is also metabolized by CYP2B6.

Indoles and their derivatives are well-known as an important class of heterocyclic compounds, their core being a near-ubiquitous component of biologically active natural products, widespread in different species of plants, animals, and marine organisms. The indole is also well-known as one of the most important scaffolds for drug discovery, capable of serving as ligand for a diverse array of receptors. Indoles is used in textile dyes, perfumes, in agriculture and veterinary medicine. Relatively new areas are dietary supplements and nutraceuticals.