Can a mass spectrum alone prove a vial contains Epitalon?

Not on its own. A rearranged tetrapeptide such as Glu-Ala-Asp-Gly has the same formula and therefore the same mass as Ala-Glu-Asp-Gly. A matching mass rules out most unrelated substitutes, but proving the order needs fragment data from tandem mass spectrometry, or a chemical step like the heating test investigators have used to tell the two apart.

Is Epithalon the same compound as Epitalon?

Yes. Epithalon and Epithalone are alternative spellings for the same tetrapeptide, Ala-Glu-Asp-Gly, listed in PubChem as CID 219042. Epithalamin is different: PubChem lists it as a synonym, but the research literature uses the name for the bovine pineal extract the tetrapeptide was modelled on, which contains many short peptides and free amino acids.

Why might an Epitalon chromatogram show a peak right next to the main one?

For Epitalon, the Asp-Gly ending can form aspartimide and isoaspartyl by-products, and racemisation during synthesis can create diastereomers. The isoaspartyl form and the diastereomers have the same mass as Epitalon, so a mass spectrum alone cannot flag them. Retention time against an authentic reference standard is what distinguishes them from the main peak.

Can amino acid analysis confirm Epitalon identity?

Only in part. Hydrolysis followed by amino acid analysis should find alanine, glutamic acid, aspartic acid and glycine in equal proportions, and it can also measure how much peptide is present. It cannot tell the order of those four residues, so it works best alongside an MS/MS result rather than in place of one.

One of the 30 compound testing profiles

Epitalon

Epitalon is a 4-amino-acid peptide (C14H22N4O9, average mass 390.35 g/mol); a test should confirm that mass and also the Ala-Glu-Asp-Gly order, because a rearranged tetrapeptide built from the same four residues weighs exactly the same.

Epitalon is a synthetic tetrapeptide, Ala-Glu-Asp-Gly, that was designed from the amino acid composition of a bovine pineal gland extract called Epithalamin (Araj et al., 2025).

Test your epitalon

Identity card

Formula: C14H22N4O9
Average mass: 390.35 g/mol
Monoisotopic mass: 390.14 Da
Length: 4 residues
Modifications: Free N-terminus; Free C-terminal acid
Also sold as: Epithalon, Epithalone, Epitalone, AEDG, Ala-Glu-Asp-Gly
Sequence: AEDG
Note: PubChem lists the line notation H-Ala-Glu-Asp-Gly-OH. All residues are the L form except glycine, which has no stereocentre.

Source: Epitalon compound record (CID 219042).

Check a certificate's mass against these values with the mass checker, prefilled for Epitalon.

What usually goes wrong with epitalon. Documented failure modes, with sources.

A rearranged tetrapeptide with the identical mass

Epitalon's four residues can be shuffled into other tetrapeptides with exactly the same formula. A 2025 review describes work by Vanhee and colleagues, who identified Epitalon in two illegal pharmaceutical preparations by LC-MS/MS and considered the risk of substitution by Glu-Ala-Asp-Gly (EADG) (Araj et al., 2025). They made the distinction absolute by heating the sample, because an N-terminal glutamic acid can cyclise to pyroglutamate and lose mass, which EADG can do and AEDG cannot. A matching mass is necessary for this peptide but not sufficient.

Aspartimide and isoaspartyl forms at the Asp-Gly end

Epitalon ends in Asp-Gly. In a systematic study of Fmoc synthesis, an Asp followed by Gly was especially prone to aspartimide formation, and aspartimide side products were assigned by a mass 18 units below the target (Samson et al., 2019). Aspartate can also rearrange into a beta-linked isoaspartyl bond (Reissner and Aswad, 2003), an isomer with the same mass as the intended chain. The first impurity shows in a mass spectrum; the second needs chromatographic separation.

Stereoisomers that share every atom

Epitalon has three asymmetric centres and so can exist as eight stereoisomers; the natural form uses only L-amino acids (Araj et al., 2025). Fmoc deprotection can cause racemisation and so diastereomeric impurities (D'Hondt et al., 2014). A diastereomer has the same formula, mass and amino acid composition as Epitalon, so only an HPLC method run against an authentic reference standard can show it, as a separate peak.

Confusion with the pineal extract it was modelled on

PubChem lists Epithalamin among Epitalon's synonyms (PubChem), but the literature uses Epithalamin for the bovine pineal extract. When that polypeptide complex was analysed by mass spectrometry and HPLC it contained free amino acids (3.26%), dipeptides (23.19%), tripeptides (50.72%), tetrapeptides (22.10%) and pentapeptides (0.72%), with AEDG detected among the tetrapeptides (Khavinson et al., 2017). An extract-type product would give a crowded chromatogram in which AEDG is one component among many, so a single-peptide purity figure does not describe it.

Which tests matter most

LC-MSTandem MS fragments read the residue order, the routine way to tell AEDG from a same-mass rearrangement such as EADG.
HPLC-UVDiastereomers and isoaspartyl forms share Epitalon's mass, so separation against a reference standard is what reveals them.
Amino acid analysisConfirms one each of Ala, Glu, Asp and Gly and gives a peptide amount, but cannot tell the order of those residues.
Counter-ion contentThe powder is weighed as a salt, so measuring the counter-ion turns a label weight into a peptide weight.

Reading epitalon results

PubChem gives Epitalon a monoisotopic mass of 390.14 Da and an average mass of 390.35 g/mol (PubChem). A report should say which of the two it compares against; the mass checker shows both.

Lyophilising a peptide after purification with trifluoroacetic acid leaves a peptide-TFA salt, and the counter-ion introduces a weighting error because the salt forms differ in molecular weight (Erckes et al., 2025). A label of 10 mg may describe the powder, the salt or the peptide; a useful amount report states which. See net peptide content and counterions.

Public Tested.ph results

No public epitalon records yet

Each public epitalon record will appear here with its identity, HPLC purity and measured amount against the label, once the first vial is tested.

FIG 13Amount against the label

Questions about testing epitalon

Can a mass spectrum alone prove a vial contains Epitalon?: Not on its own. A rearranged tetrapeptide such as Glu-Ala-Asp-Gly has the same formula and therefore the same mass as Ala-Glu-Asp-Gly. A matching mass rules out most unrelated substitutes, but proving the order needs fragment data from tandem mass spectrometry, or a chemical step like the heating test investigators have used to tell the two apart.
Is Epithalon the same compound as Epitalon?: Yes. Epithalon and Epithalone are alternative spellings for the same tetrapeptide, Ala-Glu-Asp-Gly, listed in PubChem as CID 219042. Epithalamin is different: PubChem lists it as a synonym, but the research literature uses the name for the bovine pineal extract the tetrapeptide was modelled on, which contains many short peptides and free amino acids.
Why might an Epitalon chromatogram show a peak right next to the main one?: For Epitalon, the Asp-Gly ending can form aspartimide and isoaspartyl by-products, and racemisation during synthesis can create diastereomers. The isoaspartyl form and the diastereomers have the same mass as Epitalon, so a mass spectrum alone cannot flag them. Retention time against an authentic reference standard is what distinguishes them from the main peak.
Can amino acid analysis confirm Epitalon identity?: Only in part. Hydrolysis followed by amino acid analysis should find alanine, glutamic acid, aspartic acid and glycine in equal proportions, and it can also measure how much peptide is present. It cannot tell the order of those four residues, so it works best alongside an MS/MS result rather than in place of one.

Sources

Epitalon compound record (CID 219042), PubChem, US National Library of Medicine
Araj SK et al. Overview of Epitalon, highly bioactive pineal tetrapeptide with promising properties. Int J Mol Sci. 2025;26(6):2691, International Journal of Molecular Sciences (PMC)
Vanhee C et al. Identification of the small research tetra peptide Epitalon in two illegal pharmaceutical preparations. Drug Test Anal. 2015;7(3):259-64, Drug Testing and Analysis (PubMed)
Samson D et al. The aspartimide problem persists. J Pept Sci. 2019;25(7):e3193, Journal of Peptide Science (PMC)
Reissner KJ, Aswad DW. Deamidation and isoaspartate formation in proteins. Cell Mol Life Sci. 2003;60(7):1281-95, Cellular and Molecular Life Sciences (PubMed)
D'Hondt M et al. Related impurities in peptide medicines. J Pharm Biomed Anal. 2014;101:2-30, Journal of Pharmaceutical and Biomedical Analysis (PubMed)
Khavinson VK et al. Identification of peptide AEDG in the polypeptide complex of the pineal gland. Bull Exp Biol Med. 2017;164(1):41-43, Bulletin of Experimental Biology and Medicine (PubMed)
Erckes V et al. Towards a consensus for the analysis and exchange of TFA as a counterion in synthetic peptides. Pharmaceuticals. 2025;18(8):1163, Pharmaceuticals (PMC)

Last reviewed 6 Oct 2026.