betaine

A sweet, crystalline compound (not an alkaloid), trimethylammoniumacetate, found in sugar beet and similar plants, sometimes used to treat muscular degeneracy; the zwitterion (CH₃)₃N⁺CH₂COO⁻

Any derivative of this compound.

Any similar compound, based on sulfur or phosphorus etc, having an onium ion with no hydrogen atom adjacent to the anionic atom.