A betaine (/ˈbiːtə.iːn, bɪˈteɪ-, -ɪn/) in chemistry 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.[1] Historically, the term was reserved for trimethylglycine (TMG), which is involved in methylation reactions and detoxification of homocysteine.[1] This is a modified amino acid consisting of glycine with three methyl groups serving as methyl donor for various metabolic pathways.[2]