Ergothioneine

Ergothioneine (EGT) is a naturally occurring, sulfur‑containing amino acid derivative first isolated from the mushroom Claviceps purpurea in 1909. In humans, it is taken up via the highly specific transporter OCTN1 (SLC22A4) and functions primarily as a potent intracellular antioxidant and metal‑chelating molecule, helping to maintain redox balance across a wide range of tissues.

• Ergothioneine is a thiol‑containing derivative of histidine.
• IUPAC name: (2‑S‑methyl‑3‑[2‑(sulfinyl)‑1‑hydroxy‑3‑pyrrolyl]‑L‑histidine).
• Molecular formula: C₁₀H₁₆N₂O₃S.
• Molecular weight: 229.30 g·mol⁻¹.
• Structure: A histidine backbone with a thio‑methyl group at the imidazole nitrogen and an N‑alkylated sulfur (–S–CH₃) that is oxidized to a sulfide‑sulfoxide (S–O). The 2‑sulfoxide confers strong antioxidant capacity while maintaining high water solubility (≈ 1 g/L at 25 °C). The molecule is stable at neutral pH, resistant to gastric acid, and retains activity after standard food‑processing temperatures.

• Ergothioneine is most abundant in edible mushrooms (especially Boletus spp., Pleurotus spp., and Lentinula edodes), where it can reach 4–10 mg · kg⁻¹ fresh weight.
• Commercially, EGT is extracted from cultivated mushroom mycelia using aqueous or ethanol‑based extraction followed by chromatography (e.g., ion‑exchange or HPLC) to achieve >95 % purity.
• Synthetic routes (e.g., solid‑phase peptide synthesis) are also available but are more costly.
• For supplements, quality markers include: ≥95 % purity, absence of heavy metals (<0.5 ppm), and verification of the OCTN1‑compatible stereochemistry (L‑form).
• Products certified by third‑party labs (e.g., USP, NSF) provide assurance of consistency and lack of contaminants such as mycotoxins.