Trimethylamine N-oxide

Trimethylamine N-oxide (TMAO) is the organic compound in the class of amine oxides with the formula (CH₃)₃NO. This colorless solid is usually encountered as the dihydrate. It is a product of the oxidation of trimethylamine and a common metabolite in animals. It is an osmolyte found in saltwater fish, sharks, rays, molluscs, and crustaceans. It is a protein stabilizer that may serve to counteract urea, the major osmolyte of sharks, skates and rays. It is also higher in deep-sea fishes and crustaceans, where it may counteract the protein-destabilizing effects of pressure. TMAO decomposes to trimethylamine (TMA), which is the main odorant that is characteristic of degrading seafood.

Synthesis

TMAO can be synthesized from trimethylamine by treatment with hydrogen peroxide:

TMAO is biosynthesized from trimethylamine, which is derived from choline.

Trimethylaminuria

Trimethylaminuria is a defect in the production of the enzyme flavin containing monooxygenase 3 (FMO3). Those suffering from trimethylaminuria are unable to convert choline-derived trimethylamine into trimethylamine oxide. Trimethylamine then accumulates and is released in the person's sweat, urine, and breath, giving off a strong fishy odor.

Amine oxide

An amine oxide, also known as amine-N-oxide and N-oxide, is a chemical compound that contains the functional group R₃N⁺–O⁻, an N–O bond with three additional hydrogen and/or hydrocarbon side chains attached to N. Sometimes it is written as R₃N→O or, wrongly, as R₃N=O.

In the strict sense the term amine oxide applies only to oxides of tertiary amines. Sometimes it is also used for the analogous derivatives of primary and secondary amines.

Examples of amine oxides include pyridine N-oxide, a water-soluble crystalline solid with melting point 62–67 °C, and N-methylmorpholine N-oxide, which is an oxidant.

Applications

Amine oxides are surfactants commonly used in consumer products such as shampoos, conditioners, detergents, and hard surface cleaners. Alkyl dimethyl amine oxide (chain lengths C10–C16) is the most commercially used amine oxide. They are considered a high production volume class of compounds in more than one member country of the Organisation for Economic Co-operation and Development (OECD); with annual production over 26,000, 16,000 and 6,800 metric tons in the US, Europe, and Japan, respectively. In North America, more than 95% of amine oxides are used in home cleaning products. They serve as stabilizers, thickeners, emollients, emulsifiers and conditioners with active concentrations in the range of 0.1–10%. The remainder (< 5%) is used in personal care, institutional, commercial products and for unique patented uses such as photography.