GHRP-2, GHRP-6, hexarelin and ipamorelin: structures compared

Sequences

• GHRP-6: His-D-Trp-Ala-Trp-D-Phe-Lys-NH2.
• GHRP-2 (pralmorelin): D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2 (2Nal = 2-naphthylalanine).
• Hexarelin: His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2, a methylated GHRP-6 analogue.
• Ipamorelin: Aib-His-D-2Nal-D-Phe-Lys-NH2 (Aib = α-aminoisobutyric acid), a pentapeptide.

PubChem data

• GHRP-6: C46H56N12O6, 873.0 g/mol, monoisotopic 872.445 Da.
• GHRP-2: C45H55N9O6, 818.0 g/mol, monoisotopic 817.428 Da.
• Hexarelin: C47H58N12O6, 887.0 g/mol, monoisotopic 886.460 Da (GHRP-6 + CH2).
• Ipamorelin: C38H49N9O5, 711.9 g/mol, monoisotopic 711.386 Da.

Source: PubChem CID 4345065: GHRP-6; PubChem CID 6918245: GHRP-2; PubChem CID 6918297: Hexarelin; PubChem CID 9831659: Ipamorelin

Design features

All four carry D-amino acids and a C-terminal amide, which resist proteolysis, and all end in D-Phe-Lys-NH2 or a close variant. Ipamorelin was reported in 1998 as the first GHRP-receptor agonist selective for growth hormone release in animal studies, in contrast to the broader hormone release seen with earlier GHRPs.

Source: Growth hormone-releasing peptide (GHRP), Cell Mol Life Sci 1998 (PubMed 9893708); Unnatural growth hormone-releasing peptide begets natural ghrelin, J Clin Endocrinol Metab 2001 (PubMed 11297568); Ipamorelin, the first selective growth hormone secretagogue, Eur J Endocrinol 1998 (PubMed 9849822)

Analytical notes

• Hexarelin and GHRP-6 differ by 14 Da; MS separates them easily, HPLC may not.
• Tryptophan and naphthylalanine absorb strongly at 280 nm, so these peptides are easy to detect by UV.
• Tryptophan-containing sequences are light- and oxidation-sensitive in solution.

At Sable

Sable lists these compounds as lyophilised research materials. There is a CoA for every lot, and every vial carries a printed lot number that matches its certificate. A CoA is emailed within 2 hours of a request.

Frequently asked questions