Pal-AHK

1 Identity

Acylated cosmetic tripeptide, or a copper(II) complex of one - the name as traded does not distinguish them. The metal-free article is a synthetic tripeptide Ala-His-Lys bearing a single C16:0 palmitoyl group amide-bonded to the N-terminal alpha-amino group. The copper-bearing article is a coordination compound of that ligand and is a different substance on a different analytical panel. Sold as a topical bulk cosmetic raw material. and in the topical bulk channel as "Pal-AHK Topical". Not synonyms, and each is a separate article with a separate mass: AHK-Cu, the copper complex of the free tripeptide Ala-His-Lys, which is what most of the "copper peptide" literature and marketing attached to this name is actually about.

Sequence

N-hexadecanoyl(palmitoyl)-L-Ala-L-His-L-Lys-OH, as the article is understood in the metal-free case. A single C16:0 acyl group amide-bonded to the alpha-amino group of Ala1; free C-terminal carboxylic acid on Lys3; no amidation, no cyclization, no disulfide; all three residues L and proteinogenic. The sequence statement is incomplete without two further statements that sellers do not make: (i) the REGIOCHEMISTRY, because the lysine epsilon-amine and the histidine imidazole are competing acylation and coordination sites and the attachment point is not carried in the mass; and (ii) the metal content, because a copper(II) complex of the same ligand is sold under the same name. This company treats the sequence as a supplier claim until MS/MS sequencing and an ICP-MS copper result are both on the certificate.

Molecular formula

C31H56N6O5 for the metal-free N-alpha-palmitoyl tripeptide, reconstructed from the sequence. Free ligand AHK C15H26N6O4. If copper is present, the 1:1 deprotonated complex is C31H54N6O5Cu (and 1:1 neutral-adduct and 2:1 stoichiometries are also in commerce, none of them declared). No CAS Registry Number is asserted for Pal-AHK: none was verified from a registry source, and the CAS numbers that circulate on seller pages for this name belong to palmitoyl tripeptide-1 (147732-56-7) or to AHK-Cu, not to this article. A page quoting 147732-56-7 under this name is a named red flag.

Average mass

592.83 Da (C31H56N6O5) from the reconstructed formula on IUPAC 2021 abridged conventional atomic weights, 592.826 unrounded. Reference points: free ligand AHK 354.41, which is 238.42 Da light; Pal-GHK 578.80, exactly 14.03 Da lighter, which is one methylene and the single most likely substitution; AHK-Cu, the un-palmitoylated copper article, 415.94 for the 1:1 deprotonated complex; and the 1:1 deprotonated copper complex of this ligand, C31H54N6O5Cu, 654.36, exactly 61.53 Da heavier than the metal-free article. No published average mass from a registry or standards body was located for this article, so this figure is a reconstruction and is stated as one; the name-to-structure link is not established.

Monoisotopic mass

592.43122 Da neutral (C31H56N6O5); [M+H]+ 593.43850; [M+2H]2+ m/z 297.22289. Free ligand AHK 354.20155 neutral, [M+H]+ 355.20883. Pal-GHK 578.41557 neutral, [M+H]+ 579.42285 - 14.0157 Da below this article, a difference any accurate-mass method sees and no nominal-mass method does. 1:1 deprotonated copper complex C31H54N6O5Cu 653.34519 neutral. All values are reconstructions from the assumed structure, not measurements against a reference standard.

Salt / variant note

The whole risk on this article is that the name does not fix the molecule. (1) copper state, undeclared in this market: metal-free C31H56N6O5 at 592.83 against the 1:1 deprotonated complex C31H54N6O5Cu at 654.36 - 61.53 Da apart, trivially separable by mass and by a single ICP-MS line, and routinely undeclared. Copper isotopes 63Cu and 65Cu at roughly 69:31 also give a copper-bearing lot an unmistakable isotope pattern that a metal-free lot does not have, which is a free confirmatory test on any spectrum already acquired. (2) PAL-GHK / palmitoyl tripeptide-1, C30H54N6O5, 578.80 / 578.41557 - one methylene lighter, 14.03 Da, stocked by the same sellers at the same 200 mg size and the same list price, and the single most likely substitution against this article. Pal-GHK is also routinely called a copper peptide in this market and is not one. (3) AHK-Cu, C15H24N6O4Cu at 415.94 for the 1:1 deprotonated complex - the un-palmitoylated copper article, also 200 mg on the same shelf at a higher list price. (4) free ligand AHK, C15H26N6O4, 354.41 / 354.20155 - the des-palmitoyl failure, 238.42 Da light; blended with free palmitic acid (256.42 average) it gives a plausible elemental analysis and a correct appearance while the mass spectrum shows two peaks and no conjugate. (5) REGIOISOMERS, which carry NO mass difference at all: N-epsilon-palmitoyl AHK is also C31H56N6O5 at 592.83, and only MS/MS fragmentation or co-elution against a qualified standard separates it from the N-alpha article. (6) acyl-chain axis: the myristoyl (C14:0) analogue is 28.05 Da light and the stearoyl (C18:0) analogue 28.05 Da heavy, both real ingredient classes with their own supply chains. (7) "Lipopeptide" as sold: a non-specific designation on the same shelf at 200 mg that denotes a structural class, not a molecule; it is not an identity and is never accepted against this purchase specification.

2 Class & testing panel

Form

Single article

Testing panel

P2 — panel definitionfor the metal-free lipopeptide; P5 for any copper-bearing form. The panel assignment cannot be fixed until the metal question is answered in writing

3 Primary sources & evidence

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

No compound-specific primary literature was identified for this article under its own name, in vitro, animal or human, across cosmeceutical peptide reviews, Cosmetic Ingredient Review safety assessments and targeted INCI-name searches. The literature for the group it is filed in is graded F, the lowest grade the index carries, on that basis. What exists instead, and what a catalog page must keep separate from it: (i) class-level delivery literature, Kraeling et al., Cutan Ocul Toxicol 2015, PMID 24754410 (in vitro, excised human cadaver skin and hairless guinea pig skin), and Choi et al., Biomol Ther 2014, PMID 25143811 (in vitro, hairless mouse skin), which measure where cosmetic peptides go rather than what any of them does; (ii) a systematic review of over-the-counter topical antiaging agents, Imhof and Leuthard, Dermatology 2021, PMID 32882685, whose stated position on the class is that evidence supporting these products is often lacking; (iii) a formulation and solubility citation for palmitoylated cosmetic peptides, Wang et al., Adv Sci 2025, PMID 39783908; and (iv) a single human case report of infection following facial injection of a cosmetic-grade peptide, Chen et al., World J Clin Cases 2021, PMID 33748252, cited for the documented hazard of injecting cosmetic-grade material. The GHK-Cu literature is a literature about a different molecule and does not transfer. No human trial of this article 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 assessment for this specific ingredient was identified, although the Review has assessed other peptide ingredients.

4 Storage & specification

Storage

Off-white to pale-tan lyophilized powder (blue to blue-violet if copper is present, which is itself a visual check on the metal question), acetate salt, in amber glass with a nitrogen headspace and a desiccant sachet; 2 to 8 degrees C, protected from light and moisture; equilibrated to room temperature in the sealed container before opening so that atmospheric moisture does not condense onto the powder. The palmitoyl chain makes the material amphiphilic and poorly water-soluble, so the handling page names the co-solvent system used for the assay and says nothing about administration, route or vehicle. Any copper-bearing form is additionally pH-sensitive and incompatible with chelators and strong reducing agents, and is stored and handled away from both.

Shelf life

Provisional 24-month retest interval at 2 to 8 degrees C, the class condition for an article of this type, replaced by the company's own three-lot ICH Q1A-format study - long-term at 5 degrees C plus or minus 3 degrees C, accelerated at 25 degrees C / 60 percent RH - at the 12-month data point, with free palmitic acid and des-acyl content as the stability-indicating attributes rather than total assay, and with copper content added as a stability attribute for any complexed form.