Arsenobetaine is an organoarsenic compound found primarily in fish and other marine life, as well as some fungi. It is the arsenic analog of trimethylglycine, commonly known as betaine. The biochemistry and biosynthesis of this molecule are similar to those of choline and glycine betaine.
Arsenobetaine is a common substance in marine biological systems and unlike many other organoarsenic compounds, such as trimethylarsine, it is relatively non-toxic. The compound may play a similar role as urea does for nitrogen, as a non-toxic waste compound made in the bodies of animals to dispose of the relevant element.
It has been known since 1920 that marine fish contain organoarsenic compounds, but it was not until 1977 that the chemical structure of arsenobetaine was determined.
Arsenobetaine may be synthesized in the lab from trimethylarsine and ethyl bromoacetate, followed by basic saponification of the resulting ester such as by using a Dowex 2 (HO-) exchange resin column:
Safety Whereas arsenous acid (As(OH)3) has an in mice of 34.5 mg/kg, the LD50 for the arsenobetaine exceeds 10 g/kg.
References
Further reading