The molecule is an alpha-amino-acid cation obtained by protonation of the imidazole ring of ergothioneine. It is the major microspecies at pH 7.3 (according to Marvin v 6.2.0.). It is a conjugate acid of an ergothioneine.
(2S)-3-(2-sulfanyl-1H-imidazol-3-ium-5-yl)-2-(trimethylazaniumyl)propanoate