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Molecular Weight
Purity
Storage
Appearance
Solubility
01
Ipamorelin is a synthetic five-residue peptide that acts as an agonist at the growth hormone secretagogue receptor (GHS-R1a), also known as the ghrelin receptor. It belongs to the growth hormone-releasing peptide (GHRP) family alongside GHRP-2 and GHRP-6, but works through a different receptor from GHRH analogues such as CJC-1295.
Three of its five residues are non-standard: α-aminoisobutyric acid (Aib), D-2-naphthylalanine (D-2-Nal) and D-phenylalanine (D-Phe). These give the peptide a compact, protease-resistant structure and are linked to its reported receptor selectivity. With a molecular weight of 711.85 g/mol it is one of the smallest compounds in this class. It is supplied as a lyophilized reference material for in vitro ghrelin-receptor pharmacology, selectivity comparisons and analytical work on peptides containing non-proteinogenic amino acids.
02
The sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂ combines two standard residues with three engineered ones, each with a clear structural role.
Aib, position 1
α-Aminoisobutyric acid has two methyl groups on its α-carbon instead of one hydrogen. This sharply limits backbone flexibility, favours turn-like conformations and makes the N-terminus a poor substrate for aminopeptidases.
D-2-Nal, position 3
A large, flat naphthalene ring presented with D-stereochemistry. This bulky aromatic group is a key feature for fitting the ghrelin receptor binding pocket.
D-Phe, position 4
A second D-configured aromatic residue that helps hold the aromatic groups in the arrangement the receptor recognises, while also blocking cleavage by common proteases.
Lys-NH₂, position 5
The C-terminal lysine adds a positive charge, and the amide end protects against carboxypeptidases.
Together, the Aib residue and the two D-amino acids make Ipamorelin a short, conformationally constrained peptide with few sites that standard proteases can attack.
03
Laboratory research focuses on how Ipamorelin binds and activates GHS-R1a, and how it compares with other secretagogues.
Receptor binding
Competition binding assays with radiolabelled ghrelin in GHS-R1a-expressing membranes measure its affinity relative to ghrelin, GHRP-2 and GHRP-6.
Signalling
GHS-R1a signals mainly through the Gq pathway, so assays typically measure intracellular calcium release or inositol phosphate accumulation in receptor-expressing cell lines.
Selectivity
Published studies describe Ipamorelin as a selective secretagogue: in experimental models it stimulated growth hormone release without the notable rises in ACTH and cortisol seen with some other GHRPs. This makes it a frequent comparison compound in selectivity work.
All research context described here refers to controlled in vitro and preclinical experimental systems.
04
GHS-R1a selectivity reference
Used as a benchmark in receptor panels when profiling other ghrelin-receptor ligands.
Non-standard residue methods
Its Aib, D-2-Nal and D-Phe residues make it a practical test compound for HPLC and MS methods that must handle non-proteinogenic amino acids.
Chiral analysis
With two D-amino acids, it is a convenient standard for validating chiral amino acid analysis, such as Marfey’s reagent derivatisation followed by HPLC.
Comparative stability
Run alongside GHRP-2 and GHRP-6 to compare how different non-standard residues affect proteolytic and chemical stability.
05
Storage
Store the lyophilized powder at −20 °C, sealed and desiccated. Let the vial reach room temperature before opening.
Enzymatic stability
Aib at the N-terminus and the two D-amino acids leave few sites for common proteases, so the peptide is relatively stable in serum-containing in vitro media.
Chemical stability
There is no methionine, cysteine or asparagine, so the usual oxidation, disulfide and deamidation risks do not apply. Histidine is the most sensitive residue and can oxidise under strongly oxidising conditions.
Reconstitution
Dissolves in water or dilute acetic acid. For binding assays, a DMSO stock diluted into aqueous buffer is also common.
Solutions and labware
Prepare fresh where possible, store aliquots frozen, and use low-binding polypropylene tubes.
06
The non-standard residues shape how Ipamorelin is separated, detected and confirmed.
HPLC
Reversed-phase C18 with acetonitrile/TFA gradients works well. The naphthalene ring absorbs strongly in the UV, so detection at 280 nm as well as 214 nm gives good sensitivity.
Mass spectrometry
ESI-MS in positive mode shows [M+H]⁺ at m/z 712.4 and [M+2H]²⁺ at m/z 356.7. In MS/MS, an immonium ion at m/z 170.1 marks the naphthylalanine residue, and m/z 58.1 marks Aib.
Stereochemistry
MS cannot distinguish D- from L-residues. After acid hydrolysis, Marfey’s reagent derivatisation followed by HPLC, or a chiral column, confirms that positions 3 and 4 are D-configured.
Impurity profile
Typical checks cover L-epimers at positions 3 and 4 formed during synthesis, truncated sequences, and the non-amidated free acid ([M+H]⁺ at about m/z 713.4).
07
Three: α-aminoisobutyric acid (Aib) at position 1, D-2-naphthylalanine at position 3 and D-phenylalanine at position 4. Histidine and lysine are the only standard residues.
The peptide is hydrolysed to free amino acids, which are then derivatised with Marfey’s reagent or run on a chiral column. Comparing with D- and L-standards confirms the configuration at positions 3 and 4.
It is shorter (five residues versus six), has a different molecular weight, and contains Aib, which gives a characteristic MS/MS fragment at m/z 58.1. These differences make it easy to tell apart by HPLC retention and mass.
There is no single fixed rate; it depends on temperature, pH and storage form. Racemisation is measured directly by chiral analysis at each time point, and the L-epimer content is reported against the limits in the lot specification.
No. It is supplied strictly as a reference compound for laboratory and analytical research and is not for human or animal use.
Ipamorelin Research Reference. (2026). Pure Peptides Labs Research Catalogue. Retrieved from https://purepeptideslabs.net/research-catalogue/growth-hormone-axis-research-peptides/ipamorelin/
Materials listed on this platform are supported by independent testing and published documentation for laboratory research contexts.
