2-Mercapto-L-histidine

An intermediate in the formation of L-egothioneine, a natural amino acid ubiquitously present in cells and tissues of most plants and mammalian species. In humans, L-ergothioneine is found in red blood cells, liver, kidney, brain, seminal fluid, and cataract-free lenses at concentrations ranging from 100 uM to 2 mM. L-ergothioneine is exclusively biosynthesized in fungi and mycobacteria. Hence, humans assimilate it through dietary intake. L-ergothioneine has been proven to act as an antioxidant in vivo and to afford protection from g and UV radiation as well as from singlet oxygen in vivo. Recently, it has been shown that L-ergothioneine protects isolated perfused heart against the deleterious effect of post-ischemic reperfusion. The intermediate, 2-mercaptohistine has been used for the introduction of conformational constraints into peptides via thioether linkage and for the preparation of the bactericidal products in combination with penicillanic acid and with cephalosporin derivatives.