Studies on the origin of ergothioneine in animals.

The wide-spread occurrence of ergothioneine in animals (l-3) suggests that the compound is either synthesized by several animal species or is present in common foodstuffs. However, data in the literature on this point are equivocal and contradictory. Eagles and Vars (4) suggested that the corn protein, zein, contains 2-thiolhistidine which serves as a dietary precursor of ergothioneine. Repeated attempts by other workers to identify thiolhistidine as a constituent of corn have failed (5-7). The conclusion of Potter and Franke (8) that corn-containing diets lead to increased blood ergothioneine levels in rats, and the similar conclusion of Eagles and Vars with regard to pigs, could not be confirmed by Hunter (6). Consideration of the structure of ergothioneine (I) suggests as likely