A betaine (/ˈbiːtə.iːn, bɪˈteɪ-, -ɪn/) is any neutral chemical compound with a positively charged cationic functional group that bears no hydrogen atom, such as a quaternary ammonium or phosphonium cation (generally: onium ions), and with a negatively charged functional group, such as a carboxylate group that may not be adjacent to the cationic site. They are thus zwitterions, but cannot isomerize because there is no labile hydrogen atom attached to the nitrogen atom.
Historically, the term was reserved for trimethylglycine (TMG), which is involved in methylation reactions and detoxification of homocysteine.[1]
Pronunciation
editThe pronunciation of the compound reflects its origin and first isolation from sugar beets (Beta vulgaris subsp. vulgaris), and does not derive from the Greek letter beta (β). It is commonly pronounced beta-INE or BEE-tayn.[2]
Occurrence
editThe most common natural betaine is the original betaine, N‑trimethylglycine (glycine betaine).
The related choline deprotonates to give a betaine, but the resulting anion is typically acylated under biological conditions.
Phosphonium betaines are intermediates in the some Wittig reactions.
Cocamidopropyl betaine and various derivatives are surfactants, especially in shampoos.
Glycine betaine
edit
The original betaine, N,N,N-trimethylglycine, was named after its discovery in sugar beet (Beta vulgaris subsp. vulgaris) in the nineteenth century.[3] It is a small N-trimethylated amino acid. This substance may be called glycine betaine to distinguish it from other betaines.
It serves as a methyl donor for various metabolic pathways.[4]
See also
editReferences
edit- ↑ Physicians Desk Reference (PDR) for Nutritional Supplements, 1st ed., Medical Economics div., Thomson Healthcare: Montvale, NJ, p. 46 (2001). As cited in the Hazardous Substances Data Bank entry for betaine.
- ↑ Alex Nickon and Ernest F. Silversmith (1987). Organic Chemistry, the Name Game: Modern Coined Terms and Their Origins. Pergamon. ISBN 978-0080344812.
- ↑ DNA Methylation and Complex Human Disease, Michel Neidhart
- ↑ "Betaine". LiverTox®: Clinical and research information on drug-induced liver injury. Bethesda: National Institute of Diabetes and Digestive and Kidney Diseases. 26 September 2017. PMID 31644082. Retrieved 26 August 2021 – via US National Library of Medicine.
Further reading
edit- IUPAC, Compendium of Chemical Terminology, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "betaines". doi:10.1351/goldbook.B00637