Selenoneine, a food chain component with potential neuroprotective effects against electrophilic mercury forms

Selenoneine, an antioxidant molecule analogous to ergothioneine, is not synthesized by vertebrates but can be acquired through the diet. Both selenoneine and ergothioneine contain redox-active groups: selone (-C=Se) and thioketone (-C = S), respectively. However, the reactivity of the selone group with pro-oxidant intermediates is significantly higher than that of the thioketone group. In the presence of oxygen, selenoneine undergoes oxidation to its diselenide form, which can be regenerated by a molar excess of reduced thiol groups. High levels of selenoneine have been detected in carnivorous fish, aquatic mammals, and populations consuming these species. It has been suggested that both selenoneine and ergothioneine possess health-promoting properties in humans. This chapter explores the potential protective effects of selenoneine against electrophilic mercury forms, such as methylmercury (CH₃Hg⁺) and divalent mercury (Hg^{2 +}).