What molecule am I?
L-Ergothioneine1 (EGT) is an amino acid that occurs in bacteria of the phyla Actinomycetota and Cyanobacteriota and edible mushrooms such as porcini (Boletus edulis), king oyster (Pleurotus eryngii), and shiitake (Lentinula edodes). Only a few species biosynthesize EGT; these include Mycobacterium smegmatis, and the fungi Neurospora crassa and Schizosaccharomyces pombe. Most organisms acquire EGT in their diet.
In 1909, French pharmacist–chemist Charles Joseph Tanret reported the isolation of EGT from the rye ergot fungus (Claviceps purpurea), for which he named the molecule. Two years later, George Barger and Arthur James Ewins at Wellcome Research Laboratories (London) described the “constitution” (structure) of EGT, which they called “a betaine related to histidine2”. EGT is an unusual amino acid in that it contains a quaternary ammonium cation; it is consequently an inner salt.
Because EGT is spread throughout nature by being consumed by animals and absorbed by plants from fungi and soil, it exists in many human foods. And it has come to be recognized as having positive health effects. In 2007, Janine Ey, Edgar Schömig, and Dirk Taubert* at the University of Cologne (Germany) described the dietary sources and antioxidant effects of EGT. The authors noted that the compound accumulates in cells via the organic cation transporter OCTN1; however, information about its dietary sources and functional role in humans was scarce. They found that EGT occurs mainly in mushrooms, kidney, liver, certain beans, and oat bran. They observed that EGT acts as an antioxidant in the body; but it is far less potent than glutathione3, the main intracellular antioxidant.
In 2021, however, Bindu D. Paul at Johns Hopkins University (Baltimore) revived interest in EGT by posing that it is “a stress vitamin with antiaging, vascular, and neuroprotective roles”. Having earlier classified it as a vitamin, she noted that it “possesses antioxidant and anti-inflammatory properties that confer cytoprotection” and that it crosses the blood–brain barrier. She proposed that “using genetically engineered cells and mice, it may now be possible to elucidate roles” of EGT.
[This molecule was suggested by two readers within a month of each other earlier this year.—Ed.]
1. SciFinder name: 1H-imidazole-4-ethanaminium, α-carboxy-2,3-dihydro-N,N,N-trimethyl-2-thioxo-, inner salt, (αS)-.
2. CAS Reg. No. 71-00-1.
3. CAS Reg. No. 70-18-8.
Ergothioneine hazard information*
| Hazard class** | GHS code and hazard statement | |
|---|---|---|
| Acute toxicity, oral, category 4 | H302—Harmful if swallowed |  |
| Skin corrosion/irritation, category 2 | H315—Causes skin irritation | |
| Serious eye damage/eye irritation, category 2A | H319—Causes serious eye irritation | |
| Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335—May cause respiratory irritation | |
*Compilation of multiple safety data sheets.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.
Enlicitide decanoate1, a macrocyclic proline derivative, is an orally available drug under development by Merck (Rahway, NJ) for treating high serum cholesterol, or hypercholesterolemia. Its mode of action is inhibition of the enzyme proprotein convertase subtilisin/kexin type 9, or PCSK9.
By 2024, enlicitide decanoate was in phase 3 clinical trials. In 2025, David A. Thaisrivongs, Gao Shang, and dozens of collaborators at Merck and at Chinese laboratories disclosed a total synthesis of the drug that the authors described as a “robust manufacturing process [for] large-scale production”.
This past February, Ann Marie Navar at the University of Texas Southwest Medical Center (Dallas) and investigators worldwide published the results of a 2909-participant phase 2 trial of enlicitide decanoate for reducing low-density lipoprotein (LDL) cholesterol levels. All of the subjects had a history of a major atherosclerotic cardiovascular disease event. At 24 weeks, individuals who received the medication had an average decrease in LDL levels of 57%; whereas those who received placebo had no significant change.
1. CAS Reg. No. 2861205-06-1.
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Ergothioneine
fast facts
| CAS Reg. No. | 497-30-3 |
| Empirical formula | C9H15N3O2S |
| Molar mass | 229.30 g/mol |
| Appearance | White crystals or powder |
| Melting point | 275–277 °C |
| Water solubility | ≈200 g/L (20 °C) |
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