Acetyl Hexapeptide-8 (Argireline)

1 Identity

Synthetic N-acetylated, C-amidated hexapeptide; cosmetic ingredient with a current INCI name. and Ac-EEMQRR-NH2; "Argireline" is a registered trade name owned by a cosmetic-ingredient house. acetyl hexapeptide-3 (the superseded INCI name for the identical molecule, still used by many research vendors and the commonest source of buyer confusion in this listing).

Sequence

Ac-Glu-Glu-Met-Gln-Arg-Arg-NH2; one-letter Ac-EEMQRR-NH2. Six residues, all L-proteinogenic. The N-terminal acetyl sits on the Glu1 alpha-amino nitrogen; the C-terminus is a primary amide, not the free acid, and the distinction is worth 0.98 Da. Methionine at position 3 is the oxidation-labile residue and the stability-indicating attribute; the two N-terminal glutamates make the molecule pH-sensitive in solution. No cysteine, no disulfide, no D-residue and no non-proteinogenic residue — stated explicitly so that P3 is not applied by reflex. The sequence is written verbatim as Ac-EEMQRR-amide in Blanes-Mira 2002 (PMID 18498523) and in Kraeling 2015 (PMID 24754410); it is patterned on the N-terminal region of SNAP-25, which is a design statement about the molecule and not a statement about anything it does.

Molecular formula

C34H60N14O12S (free base). Normally supplied as the acetate or trifluoroacetate salt, with the counterion identified and quantified rather than assumed. The formula and both masses stand independently of any registry entry, reconstructed from the sequence that two peer-reviewed papers state verbatim. CAS 616204-22-9 is commonly published for this molecule but is not registry-confirmed, and identity is not asserted on it.

Average mass

889.00 Da for C34H60N14O12S. The formula with IUPAC 2021 conventional atomic weights gives 888.9998. Listings commonly print 888.98, which sits 0.02 Da below that and is an atomic-weight-table artifact rather than an error of substance; the value carried on our specification is 889.00, and the discrepancy is stated rather than silently absorbed.

Monoisotopic mass

888.4236 Da. [M+H]+ 889.4309; [M+2H]2+ 445.2191; [M-H]- 887.4163.

Salt / variant note

(1) the isobaric trap, and it is inside this same catalog. Ac-LKKTETQ, the acetylated thymosin beta-4 fragment 17-23 sold as TB-500, C38H68N10O14, 889.02 average / 888.4917 monoisotopic. Against this molecule's 889.00 average and 888.4236 monoisotopic, the average masses are 0.02 Da apart — beyond the reach of any average-mass tolerance stated in this channel — and the monoisotopic masses are 0.0681 Da apart, which is 77 ppm at m/z 889. Trivially resolvable by HRMS at a 10 ppm tolerance; completely invisible at unit resolution. Seven residues against six, free acid against amide, one contains sulfur and the other does not, and both are sold in the same catalogs. Resolving the pair is a named release requirement on both records. (2) The free-acid form Ac-EEMQRR-OH, C34H59N13O13S, 889.98 average / 889.4076 monoisotopic — 0.98 Da heavier and inside any tolerance stated in whole daltons. (3) The des-acetyl peptide H-EEMQRR-NH2, C32H58N14O11S, 846.96 average / 846.4130 monoisotopic — the direct process residue when the acetylation step is incomplete, 42.04 Da lighter. (4) Methionine sulfoxide, C34H60N14O13S, 905.00 average / 904.4185 monoisotopic — plus 16.00, the degradation species, and the reason the nitrogen flush is a specification. (5) SNAP-8, also called acetyl octapeptide-3, routinely sold as a stronger version of this molecule and marketed on this molecule's own mechanism study; its sequence, molecular weight and CAS are vendor-asserted only, with no independent source located, so no mass is asserted for it here. (6) the trade-solution variant, which is a ten-fold assay difference rather than a chemical one: cosmetic-ingredient suppliers ship an aqueous or aqueous-glycerin solution of the peptide, so "10 percent Argireline" on a label almost always denotes the supplier's dilute trade solution and not 10 percent peptide content. (7) The naming variant: acetyl hexapeptide-3 and acetyl hexapeptide-8 are the same molecule under a superseded and a current INCI name, and a certificate using either is acceptable only if the sequence and the mass are on it.

2 Class & testing panel

Form

Single article

Testing panel

P1 — panel definition

3 Primary sources & evidence

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

Published literature exists across five study types and is unusually well documented for a cosmetic peptide. In vitro SNARE and neurotransmitter-release assay, plus an uncontrolled human skin-topography arm with developer-affiliated authors and the number of volunteers not stated in the published abstract: Blanes-Mira C et al., Int J Cosmet Sci 2002;24(5):303-10, PMID 18498523. Randomized placebo-controlled human trial, n=60, 3:1 active to placebo, periorbital, twice daily, 4 weeks: Wang 2013, PMID 23417317 — the strongest single citation attaching to this ingredient. Randomized human trial in a second setting, n=24, reported as not reaching significance: Lungu 2013, PMID 23146065. In vitro skin-diffusion study on excised human cadaver skin and hairless guinea pig skin, which is the penetration evidence: Kraeling 2015, PMID 24754410. Expert-panel regulatory and toxicological safety assessment, concluding safety in cosmetics at concentrations up to 0.005 percent and data insufficient above that concentration: Johnson 2025, PMID 40673537. Formulation stability in cosmetic emulsions: PMID 17520155. Analytical and quality-control method literature: PMID 33482052. Keratinocyte and fibroblast cytotoxicity and mechanobiology: PMID 24644551, PMID 30416406. Documented injection-related infection case report: PMID 33748252. Evidence grade C.

4 Storage & specification

Storage

White lyophilized powder in a Type I amber glass vial with nitrogen-flushed headspace, elastomeric stopper and aluminum crimp seal, or in a bulk amber jar with desiccant for cosmetic raw-material quantities. Labeled: store at -20 degrees C plus or minus 5 degrees C, desiccated, protect from light and moisture, equilibrate the sealed container to room temperature before opening. The nitrogen flush is a specification and not a preference — methionine at position 3 is oxidation-labile. Reconstituted aqueous solution is markedly less stable than the dry powder, is refrigerated and used promptly, and is never held at ambient pH extremes given the two N-terminal glutamates. Aqueous trade solutions supplied by cosmetic-ingredient houses have their own storage condition, which is not this one, and their labels are not to be conflated with the bulk peptide's. Ships ambient with a labeled cumulative excursion allowance of 120 hours at or below 30 degrees C on the shipping record; lyophilized material tolerates that, and the tolerance is recorded on the shipping record rather than on the vial label.

Shelf life

Provisional 24 months at -20 degrees C plus or minus 5 degrees C from the date of QA release, stated as provisional pending the company's own stability data. Extension to 36 months only on real-time data at 12, 18, 24 and 36 months, supported by accelerated data at 40 degrees C and 75 percent relative humidity at 1, 3 and 6 months, with methionine sulfoxide, total related substances and Karl Fischer water as the stability-indicating attributes. Formulation stability of this peptide in cosmetic emulsions has been formally studied and published (PMID 17520155), which informs a customer's formulation shelf life and does not substitute for ours. Every unit carries a printed retest date and the inventory system enforces first-expiry-first-out against that date, not against receipt date.