What Ipamorelin Is: The Pentapeptide vs GHRP-2 and GHRP-6

The content, articles and product information provided on this website are strictly educational and informational. They are intended to be used for in vitro research only. “In vitro” is a Latin phrase, “in glass,” that refers to research that is conducted outside of a living organism. Note, these products are not pharmaceuticals or medicines and have not been approved by the FDA for the diagnosis, treatment or prevention of any illnesses or disorders. These products are legally prohibited from human or animal consumption.

“GHRP” is a family nickname. It is not a structure.

Ipamorelin is a five-residue synthetic peptide, sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2, formula C38H49N9O5, mass 711.9 g/mol, CAS 170851-70-4. The catalog listing is a 5 mg lyophilized vial. GHRP-2 (~818 Da), GHRP-6 (~873 Da), and hexarelin (~887 Da) are hexapeptides. Those masses do not overlap. A competent ESI-MS reading will assign the family member in one shot, provided the operator is looking at the mass and not only at HPLC area percent.

Ipamorelin is the pentapeptide at 711.9 g/mol. GHRP-2, GHRP-6, and hexarelin are hexapeptides at higher mass.

Five residues, every position specified

Position 1 is 2-aminoisobutyric acid (Aib), a non-coded α,α-disubstituted amino acid. Position 2 is histidine. Position 3 is D-2-naphthylalanine (D-2-Nal). Position 4 is D-phenylalanine. Position 5 is lysine, C-terminally amidated. The C-terminal amide is part of the structure. A free-acid analogue would be a different molecule with a different mass.

Because Aib and D-2-Nal are not among the twenty proteinogenic L-amino acids, a standard protein-sequencing assumption will mis-assign the chain. Identity is not “a 712 Da peptide.” Identity is this residue order, this stereochemistry, and this amide.

D-2-Nal is the distinctive chromophore. The naphthyl side chain absorbs well above the peptide-bond region. GHRP-6 and hexarelin carry tryptophan. Ipamorelin does not. A UV spectrum of the main HPLC peak is a cheap orthogonal check when the question is naphthyl versus tryptophan.

The catalog lists this peptide as a 5 mg lyophilized research peptide, USA manufactured, QC tested, 99%+ by HPLC and Mass Spectrometry, with a certificate of analysis as documentation. Those claims attach to this pentapeptide. They do not transfer to a hexapeptide in the same drawer.

The realistic mix-up is a nickname, not a 160 Da error

Labs do not usually receive an 873 Da peptide sold as 712 Da. The realistic failure is paperwork: a freezer box labeled “GHRPs,” a method that says “the secretagogue,” two certificates that both report 99% by HPLC. HPLC area percent is the fraction of detected peak area assigned to the main component. It does not name the component.

Ipamorelin at 99% and GHRP-6 at 99% can look equally clean. The masses do not. 711.9 g/mol versus ~873 Da is larger than typical calibration error.

A second identity problem sits in the same catalog. The CJC-1295 + ipamorelin blend is a 2 mg / 2 mg co-lyophilized cake: ipamorelin plus CJC-1295 no DAC (Modified GRF 1-29, ~3368 Da). An HPLC trace of that vial should show at least two peptide peaks. A mass spectrum should show both envelopes. Reporting a single 99% figure against that SKU, or treating the blend as “ipamorelin,” is an identity error.

Cake, freezer, diluent

Ipamorelin ships as a white to off-white lyophilized cake. Dry storage is the stable state: protected from moisture and light, commonly at −20 °C. Warm the closed vial to room temperature before opening so condensate does not form on the cake. Keep the stopper time short. Return the dry remainder to cold, dry storage.

The catalog vehicle is bacteriostatic water: sterile water with 0.9% benzyl alcohol, used so a reconstituted stock can be sampled more than once. The preservative is a property of the diluent. Two handling points matter for this pentapeptide. First, it is not highly hydrophilic. Operators who drive solvent onto the cake and then shake the vial create foam and surface film. Second, benzyl alcohol becomes part of the sample matrix. Any later HPLC of the reconstituted stock should use a blank in the same vehicle.

This article does not assign volumes or mix ratios. Name the peptide lot, the observed mass, and the diluent. That is the handling record. Reconstituted stocks are refrigerated (2–8 °C) for short-term use. Freeze-thaw of the parent aqueous vial is a poor control.

GHSR-class assays will respond to more than one analogue in this family. The selectivity that makes this pentapeptide a useful tool compound is a property of this sequence. If the vial is a different analogue, that claim does not transfer. Confirm 711.9 g/mol before the assay, not after.

What this page is not

This page is not a mix-ratio protocol. It does not assign milliliters of bacteriostatic water. It is the catalog comparison: pentapeptide versus hexapeptides, 711.9 g/mol versus 818–887 Da, plus the co-lyophilized blend that already contains this pentapeptide as one of two components.

GHRP-2, GHRP-6, and hexarelin appear here as mass contrast. They are not catalog links. Do not add them as product pages.

How the 5 mg cake actually sits in a freezer

A white cake labeled with a vendor code is not a sequence. Write Aib-His-D-2-Nal-D-Phe-Lys-NH2 or CAS 170851-70-4 on the working tube. If a chromatogram of “the GHRP vial” shows a main peak at ~873 Da, stop. That is not ipamorelin.

Catalog material is QC tested and listed at 99%+ with HPLC and Mass Spectrometry. A 99% peak at the wrong mass is still the wrong analogue. Research peptides in this line have been listed since late 2010. Use that identity package to keep the pentapeptide, the hexapeptides, and the blend on separate lines in the inventory.

Conclusion

Ipamorelin is Aib-His-D-2-Nal-D-Phe-Lys-NH2, 711.9 g/mol, CAS 170851-70-4. GHRP-2, GHRP-6, and hexarelin are hexapeptides at 818–887 Da. They share a receptor class. They do not share a mass or a catalog row.

For in vitro laboratory use, the catalog lists lyophilized ipamorelin as the 5 mg pentapeptide, the CJC-1295 + ipamorelin blend as a two-peptide cake, and bacteriostatic water as the preserved aqueous vehicle. Confirm the mass. Store the cake at −20 °C. Do not let “GHRP” stand in for a sequence.