Ipamorelin

Ipamorelin is a synthetic pentapeptide with sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. Molecular formula C38H49N9O5, theoretical monoisotopic mass 711.3856 Da, average mass approximately 711.86 Da. CAS registry: 170851-70-4.

The molecule contains three non-natural residues: Aib (α-aminoisobutyric acid) at the N-terminus, 3-(2-naphthyl)-D-alanine at position 3, and D-phenylalanine at position 4. The C-terminus is amidated. This combination of D-residues, the naphthyl side chain, and the Aib cap confers receptor selectivity for GHS-R1a and high resistance to peptidases.

Ipamorelin is produced by Fmoc solid-phase peptide synthesis on a Rink-amide-style resin (to deliver the C-terminal amide). The main impurity sources are:

• Racemization at D-2-Nal and D-Phe. Under repeated piperidine deprotection a small fraction can racemize to the L-isomer; the resulting LL diastereomer is nearly co-eluting with the parent on standard achiral HPLC.
• Loss of the C-terminal amide. Cleavage conditions that over-acidify can hydrolyze the amide to a free acid, which is a distinct analyte by mass (-1 Da) and by retention.
• Histidine oxidation. The imidazole ring is susceptible to oxidation during storage.

Additional analytes seen in real batches: truncations, deletion sequences, and residual TFA counter-ion. See common peptide impurities for the broader taxonomy.

The standard CertikLabs panel for an ipamorelin batch:

• RP-HPLC purity (C18, 0.1% TFA / MeCN, UV 214 nm)
• LC-MS identity (ESI, theoretical [M+H]+ 712.39)
• Quantitative AAA for content (note: D-2-Nal does not back-hydrolyze quantitatively, requires reference standard)
• Chiral HPLC or Marfey's analysis to confirm D-residue stereochemistry
• Ion chromatography for TFA / acetate counter-ion

Chiral confirmation matters more here than for an all-L peptide — without it, a racemized batch can pass mass-spec identity and HPLC purity and still be the wrong molecule pharmacologically.

Selective agonist of the growth-hormone secretagogue receptor (GHS-R1a, the ghrelin receptor). In published animal and early-phase human work it stimulates pituitary growth-hormone release without the parallel rise in ACTH, cortisol, or prolactin seen with non-selective secretagogues such as GHRP-6.

Primary sources:

• Raun K. et al., Ipamorelin, the first selective growth hormone secretagogue.(PMID 9849822)
• Gobburu J.V. et al., Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone-releasing peptide.(PMID 10460063)

CertikLabs does not publish dosing, administration routes, or clinical recommendations for ipamorelin.

Lyophilized ipamorelin is generally stable at -20°C protected from light and moisture. Reconstituted in aqueous solution it is sensitive to oxidation and adsorption; the C-terminal amide can also be slowly hydrolyzed to the free acid at elevated pH. Analytical re-verification of any working solution is the only reliable confirmation of integrity.