Semax: identity, regulatory status and what to check

Semax is a synthetic heptapeptide, sequence MEHFPGP, CAS 80714-61-0, formula C37H51N9O10S, calculated mass 813.92 g/mol. It holds no marketing authorisation in the United Kingdom or the European Union. Its methionine residue is the practical handling issue, and the reason a certificate for it should show an impurity table rather than a single figure.

Nomenclature: Semax, ACTH(4-7)PGP, MEHFPGP

Semax is built from two parts. The first four residues, Met-Glu-His-Phe, are the ACTH(4-7) fragment of corticotropin. The three that follow, Pro-Gly-Pro, are not part of any hormone sequence: they are a synthetic tail. Public chemical records file the compound under that construction rather than under the trade name - the entry at PubChem CID 9811102 is titled "ACTH (4-7), Pro-Gly-Pro-" and gives the formula C₃₇H₅₁N₉O₁₀S with a mass of about 813.9. Listings also write it ACTH(4-7)PGP, or by the one-letter sequence MEHFPGP.

The compound has a research literature, much of it originating in Russian publications and some continued elsewhere; it can be searched on PubMed. Peptorium does not summarise that work, does not carry it across to people or animals and runs no clinical research. Naming the fragment the sequence derives from is nomenclature, not a statement about what a vial does.

Identity: the methionine problem

The N-terminal residue is methionine, and methionine is the residue most prone to oxidation of any in a peptide of this kind. The oxidised form, the sulfoxide, is 16 daltons heavier than the parent. That single fact is the most useful thing on this page for a buyer, for two reasons.

First, it means a certificate showing only a headline purity figure is particularly weak for this compound: the sulfoxide is a distinct, predictable impurity that a proper HPLC report would resolve and name, and its absence from an impurity table is either a good result or a sign that the report was not looking. Second, it means storage and handling are not decorative. A lyophilisate kept cold, dark and dry is stable in a way that the same material left in solution at room temperature is not, and oxidation is one of the mechanisms behind that difference.

The sequence contains no cysteine, so there are no disulfide bridges to worry about, and the peptide dissolves readily in water and aqueous buffers.

Regulatory status in the UK and the European Union

Semax holds no marketing authorisation in the United Kingdom or the European Union. It does not appear in the EMA medicines database. Its status in other jurisdictions is a separate matter and is not evidence about this one: a substance registered somewhere else is still an unauthorised medicinal product here, and regulation 46 of the Human Medicines Regulations 2012 prohibits selling, supplying or offering one. Regulation 2 defines a medicinal product by presentation as well as by function, so how a seller describes a substance can bring it inside the definition without changing the substance at all.

"Research use only" is a purpose, not a permission

The phrase records the seller's intended purpose: laboratory work, not use in people. It is not a category in UK or EU law, not a licence, and not a review by any authority. It is not a quality claim, and a listing that uses it in place of saying who made the material and what was measured has answered a different question.

Purity, peptide content and the impurity table

Purity by HPLC is the proportion of separated peak area belonging to the target. Peptide content is the proportion of the vial's mass that is peptide at all, the rest being residual water and counter-ions from synthesis. Water is measured separately by Karl Fischer titration, and neither figure follows from the other. For Semax the impurity table carries more information than the headline figure, because the expected impurity - the methionine sulfoxide - is identifiable by its 16-dalton offset and should be named rather than folded into an anonymous remainder. The certificate guide and the purity guide go through the full document.

What Peptorium publishes about this material

This page publishes identity: the sequence, the molecular formula and a calculated mass of 813.92 g/mol. Each of those can be checked against a public register rather than taken on trust. Purity, peptide content and water describe one batch rather than a compound. Those figures belong on a certificate of analysis issued by the laboratory that tested that batch, and they travel with the material itself.

What to ask before buying

• Does the certificate report a measured mass beside the theoretical 813.92 g/mol?
• Is the methionine sulfoxide named in the impurity table, or is there simply no impurity table?
• Is there a batch number, and a certificate for that batch rather than one reused across the product?
• Is peptide content stated separately from purity, with water by Karl Fischer?
• Are the method and the test date named, and can the result be checked with the laboratory that produced it?
• What storage was the material held in before it was shipped?

What is not known

• What a particular vial contains cannot be known without analysing it.
• How much oxidation a given lot has undergone since it was tested is not knowable from a certificate written before it travelled.
• Storage guidance is convention for lyophilised peptides, not a stability measurement on a specific lot.

Frequently asked questions

The lyophilisate is dissolved in bacteriostatic water, and the volume of solvent chosen fixes the concentration of the solution; the peptide calculator converts between vial content, solvent volume and concentration, and recommends no quantity for any purpose. Material described here is for laboratory and in vitro research use only - see the research declaration.