Betaine is an alkaloid with the chemical name N, N, N-trimethylglycine. Its chemical structure is similar to amino acids, belonging to the quaternary ammonium base group, and its molecular formula is C5H11NO2.

Betaine is widely present in plants and animals. In plants, lycium barbarum and leguminous plants all contain betaine. Beet molasses are the main source of betaine. Among animals, molluscs such as octopus, cuttlefish, shrimp, and vertebrates (including humans) contain betaine in their liver, spleen, and amniotic fluid