l-Ergothionine hydrochloride is a sulfur-containing amino acid, which is only produced by Actinomycetales bacteria and non-yeast like fungi belonging to the division Basidiomycota and Ascomycota. It was originally isolated from Claviceps purpurea or rye ergot. It is obtained from L-histidine, which is converted into betaine form called hercynine. It is found in both animals and plants, and mammals usually obtain it from their diet, e.g. through mushrooms or oats. It is tautomeric in nature, and in neutral aqueous solution exists in thione form.
