Ergothioneine is a thiol/thione molecule synthesised only by some fungi and bacteria.
It is avidly taken up from the diet by humans and other animals through a transporter, OCTN1, and accumulates to high levels in certain tissues.
Ergothioneine is not rapidly metabolized, or excreted in urine and is present in many, if not all, human tissues and body fluids.
Ergothioneine has powerful antioxidant and cytoprotective properties in vitro and there is evidence that the body may concentrate it at sites of tissue injury by raising OCTN1 levels.
Decreased blood and/or plasma levels of ergothioneine have been observed in some diseases, suggesting that a deficiency could be relevant to the disease onset or progression.
Barry Halliwell Irwin K. Cheah Richard M. Y. Tang. Ergothioneine – a diet‐derived antioxidant with therapeutic potential. FEBS Letters In a Nutshell. Volume592, Issue20, October 2018, Pages 3357-3366.