Nonapeptide-1

1 Identity

Synthetic nonapeptide, C-terminally amidated, containing two D-amino acid residues. An analogue of the alpha-MSH C-terminal region. Sold principally as a cosmetic topical bulk active and secondarily as a research chemical.

Sequence

H-Met-Pro-D-Phe-Arg-D-Trp-Phe-Lys-Pro-Val-NH2. Nine residues, free N-terminal alpha-amine on methionine, C-terminal amide on valine. Two D-residues: D-phenylalanine at position 3 and D-tryptophan at position 5. That is the single most consequential fact on this record and it is the reason the panel is P3 rather than P1 - a chiral method is mandatory, not optional, because the all-L impurity is exactly isobaric with the product at every position. Related to the alpha-MSH C-terminal sequence: alpha-MSH is Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2, so this article corresponds to the Met-...-Pro-Val stretch with His replaced by Pro at the third position of the core and Gly replaced by Phe. No cysteine, no disulfide, no lipid, no PEG, no metal. One methionine and one tryptophan, both oxidation-labile; supplied as the acetate or trifluoroacetate salt with the counterion declared. The sequence as stated appears on three independent seller monographs, and the formula below was reconstructed from it rather than copied from any of them.

Molecular formula

C61H87N15O9S (free base, C-terminal amide). The free acid, which this article is not, would be C61H86N14O10S.

Average mass

1206.523 Da from C61H87N15O9S on IUPAC 2021 abridged conventional atomic weights. Three seller monographs print 1206.5 and a fourth prints 1206.52, all of them consistent with this formula. The arithmetic also settles the C-terminus independently of any supplier statement: the free acid of the same sequence is C61H86N14O10S at 1207.507 average, a full dalton heavier, so the published formula can only be the amide. That is a check a buyer can run without an instrument.

Monoisotopic mass

1205.6532 Da neutral monoisotopic from C61H87N15O9S. [M+H]+ 1206.6605; [M+2H]2+ 603.8339. Named degradants by arithmetic: methionine sulfoxide C61H87N15O10S at 1222.522 average / 1221.6481 monoisotopic, exactly +15.9949; the sulfone at +31.9898; tryptophan mono-oxide at +15.9949 as well, which means a single +16 peak does not tell the analyst which residue oxidized and MS/MS site localization is required to say.

Salt / variant note

(1) the all-L diastereomer, H-Met-Pro-L-Phe-Arg-L-Trp-Phe-Lys-Pro-Val-NH2: identical formula C61H87N15O9S, identical average 1206.523, identical monoisotopic 1205.6532, identical [M+H]+. It is invisible to every achiral method and to mass spectrometry at any resolving power, and it is cheaper to make, because Fmoc-D-Phe-OH and Fmoc-D-Trp-OH cost more than their L counterparts. Single-position epimers at either D-center are equally isobaric. This is the substitution the specification exists to catch: an article of this kind released against a generic peptide panel could ship the all-L diastereomer, identical in formula and in both masses and cheaper to make, without a single test on the certificate registering it. (2) The C-terminal free acid, C61H86N14O10S, avg 1207.507 / mono 1206.6372 - exactly +0.984 Da, invisible on a unit-resolution instrument. (3) Methionine sulfoxide, C61H87N15O10S, avg 1222.522 / mono 1221.6481, +15.9949, with the sulfone at +31.9898; tryptophan mono-oxide carries the same +15.9949 increment, so a +16 peak is ambiguous between two residues without MS/MS. (4) N-terminally acetylated species, C63H89N15O10S, avg 1248.560 / mono 1247.6638, +42.0106 - a real synthesis by-product where capping is used. (5) Cross-shelf substitution within the group this article is filed in: Decapeptide-12, Vialox / pentapeptide-3, Leuphasyl / pentapeptide-18, SYN-AKE, SYN-COLL / palmitoyl tripeptide-5, palmitoyl tetrapeptide-7, AHK-Cu, Pal-GHK, Pal-AHK, and the non-identity "Lipopeptide" - each is a separate article and several are sold at similar per-vial prices, which makes cross-substitution economically flat and therefore easy. The channel pricing runs against the chemistry as well: the consumer-channel 200 mg unit sits below the institutional-channel 200 mg unit on a molecule whose D-residues are the expensive part to make. (6) alpha-MSH itself, C77H109N21O19S, avg 1664.907 / mono 1663.7929, nowhere near this article's mass and never a legitimate substitute for it. Salt form is a further axis: acetate 60.052 or trifluoroacetate 114.023 per equivalent, undeclared by every monograph found.

2 Class & testing panel

Form

Single article

Testing panel

P3 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Published literature exists for the group this article is filed in and is graded F, the lowest grade the index carries. That grade records that no compound-specific primary evidence, in vitro, animal or human, was identified for any member of that group, that the marketed mechanisms are analogies to better-characterized molecules, and that the efficacy claims trace to seller technical literature rather than to independent peer-reviewed sources. Identifiers that do exist and belong to the class rather than to this molecule: Imhof L, Leuthard D 2021, PMID 32882685, systematic review of over-the-counter topical antiaging agents; Kraeling MEK et al. 2015, PMID 24754410, in vitro human cadaver and hairless guinea pig skin penetration study on acetyl hexapeptide-8; Choi YL et al. 2014, PMID 25143811, in vitro hairless mouse skin study on the collagen pentapeptide pair. Seller monographs print receptor-affinity figures for this molecule against four melanocortin receptors. Those are unsourced assertions rather than primary literature: neither a citation nor a study design is attached to them at source, and this record neither repeats the figures nor treats them as evidence. No human trial of this molecule was identified and no NCT number is quoted because none was found; that is an absence of identified record rather than a certified absence. No Cosmetic Ingredient Review Expert Panel assessment for this specific ingredient was identified, although the Panel has assessed other peptide ingredients.

4 Storage & specification

Storage

White to off-white lyophilized or spray-dried powder, acetate or trifluoroacetate salt as declared, in Type I amber glass under nitrogen, stoppered and crimped. Store at -20 degrees C plus or minus 5 degrees C, desiccated over silica, protected from light. Light protection is not boilerplate on this article: tryptophan is photolabile and methionine is oxidation-labile, and both degrade to species at the same +16 nominal increment. Inert headspace at fill. Equilibrate the sealed vial to room temperature before opening; the salt is hygroscopic and the label carries a close-immediately-after-weighing instruction. Ships ambient with a labeled cumulative excursion allowance of 120 hours at or below 30 degrees C, gel packs at 2 to 8 degrees C beyond that, single-use temperature logger in every export carton. Not stored reconstituted.

Shelf life

Provisional 18-month retest interval at -20 degrees C plus or minus 5 degrees C, desiccated, light-protected and under inert headspace, stated as provisional pending this company's own stability data. Eighteen rather than twenty-four because the sequence carries both an oxidation-labile methionine and a photolabile tryptophan; the catalog applies the shorter provisional interval wherever a methionine is present. The confirming study is an ICH Q1A(R2) design with methionine sulfoxide, tryptophan oxidation products and water as the stability-indicating attributes, plus a photostability arm to ICH Q1B, at 0, 3, 6, 9, 12 and 18 months at -20 degrees C with 2 to 8 degrees C and 25 degrees C / 60 percent RH arms. Chiral purity is re-measured at the 12-month and terminal points, because epimerization on storage is a slow process that no achiral stability-indicating method would reveal. Printed retest date on every vial, first-expiry-first-out enforced against it.