Wikipedia
Ergothioneine is a naturally occurring amino acid and is a thiourea derivative of histidine, containing a sulfur atom on the imidazole ring. This compound is made in relatively few organisms, notably Actinobacteria, Cyanobacteria, and certain fungi. Ergothioneine was discovered in 1909 and named after the ergot fungus from which it was first purified, with its structure being determined later, in 1911.
In vitro assays, as well as in vivo animal models, are used in basic research to identify its potential biological properties.
In humans, ergothioneine is acquired exclusively through the diet and accumulates in erythrocytes, bone marrow, liver, kidney, seminal fluid and the eyes. Ergothioneine requires a specific transporter, ETT, also known as OCTN1 (gene symbol SLC22A4), to enter cells. ETT expression has been confirmed in human and animal cell lines and its functional ability to transport ergothioneine has been confirmed in vivo. Although the effect of ergothioneine in vivo is an active area of research, its physiological role in humans is undetermined.