Індол

Indole — at low concentration floral, at high concentration animalic — is the marker of indolic white florals; central to PREMIEREPEAU's Nuit Élastique in its sambac jasmine heart.

Properties

Indole has the formula C₈H₇N and a molecular weight of 117.15. It is a solid at room temperature that melts at 52 to 54 °C and boils at 253 to 254 °C. Its solubility in water is 0.19 g/100 ml at 20 °C. Indole is soluble in ethanol, fixed oils and propylene glycol, and insoluble in glycerol. It is not very stable on exposure to light and turns red.

Chemistry

Indole is classified as an aromatic heterocycle. Indole is planar, with 10 π-electrons in a completely conjugated system. The ring is a π-excessive heteroaromatic system because of the electron-donating character of the pyrrole-type nitrogen atom, and the π-system is relatively electron-rich, particularly at carbon C-3. Its dipole moment is 2.11 D in benzene. It undergoes electrophilic substitution, mainly at position 3. The hydrogen atom attached to the nitrogen can be replaced by alkali metals, and reactions with acids give diindole, triindole and polymer products. Oxidation of indole yields indigo, while mild hydrogenation produces 2,3-dihydroindole (indoline). Substituted indoles are structural elements of the tryptophan-derived tryptamine alkaloids, which include the neurotransmitter serotonin. Indoles and their derivatives are promising against tuberculosis, malaria, diabetes, cancer, migraines, convulsions and hypertension.

Indole-based compounds

The tryptophan-derived tryptamine alkaloids also include the hormone melatonin and the naturally occurring psychedelic compounds dimethyltryptamine and psilocybin. Other indolic compounds include the plant hormone auxin (indole-3-acetic acid), tryptophol, the anti-inflammatory drug indomethacin and the beta-blocker pindolol. Anti-migraine drugs of the triptan class are often made by the Fischer indole synthesis.

Occurrence and biosynthesis

Indole occurs naturally in human feces and in coal tar. Bacteria can produce it as a degradation product of the amino acid tryptophan. The first step of that pathway is the cleavage of tryptophan by the enzyme tryptophanase, which produces indole, pyruvate and ammonia. The pathway is found mainly in bacteria and fungi, and it can also be active in mammalian tissues such as the liver and intestine. Tryptophan can also be degraded through the kynurenine pathway, which is mainly involved in the production of niacin (vitamin B3) but also produces indole derivatives. In the liver, indole can be metabolized into indoxyl sulfate, a compound that is toxic in high concentrations. Indole is a constituent of many flower scents, such as orange blossoms. It has been found in Robinia pseudacacia, the jasmines, and certain citrus plants. Natural jasmine oil contains around 2.5% of indole, and orange blossom oil 0.1%. Indole has also been identified in cannabis, and it is a natural component of tobacco smoke.

Stability and handling

Indole is stored in a cool, dry place in tightly sealed containers, protected from heat and light, and its shelf life is 36 months or longer if stored properly.

In the PREMIEREPEAU collection, indole's narcotic florality is structural to Nuit Élastique, where it inhabits the jasmine sambac and grandiflorum absolutes that form the composition's heart — thickening the floral accord into something nocturnal, bodily, and slow.

This note in PREMIEREPEAU. Nuit Élastique. Sample all seven extraits in the Discovery Set.