Category: metabolite
Aliases: L-Ergothioneine, ERG, EGT, Thiolhistidine betaine
Sulfur-containing thiohistidine betaine synthesised only by certain fungi and mycobacteria — humans obtain ergothioneine exclusively through diet. Actively imported into cells via SLC22A4 / OCTN1 (the 'ergothioneine transporter' ETT) — the high-affinity, highly-specific transporter expressed in erythrocytes, kidney, lung, eye, and brain. Plasma half-life on chronic dosing is ~30 days (ETT-mediated tissue retention). Functions as a potent scavenger of hydroxyl radical, singlet oxygen, and HOCl; also chelates Cu²⁺ / Fe²⁺. Low plasma levels associate with age-related neurodegeneration (Cheah 2016). The 'longevity vitamin' hypothesis (Ames 2018) argues humans evolved a dedicated transporter for a reason.