What hexarelin is
Hexarelin is a synthetic hexapeptide with the sequence His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2. It belongs to the growth hormone releasing peptide (GHRP) family, a series of short peptides developed from the late 1970s onwards that act at the ghrelin receptor, GHS-R1a, rather than at the GHRH receptor. Hexarelin was described in the early 1990s by Deghenghi and colleagues as an analogue of the earlier GHRP-6, in which the second residue is replaced by 2-methyl-D-tryptophan to improve stability.
The receptor through which the GHRPs act, GHS-R1a, was cloned in 1996 and its endogenous ligand ghrelin identified three years later, so hexarelin is now described as a ghrelin receptor agonist. The published literature also reports that it binds the scavenger receptor CD36. The two D-amino acids and the methylated tryptophan make the chain resistant to proteolysis. The C-terminus is amidated. The average molecular weight is approximately 887 g/mol and the CAS number is 140703-51-1.
The published literature on the compound, with references, is collected in the monograph.
What you receive
Each vial contains hexarelin as a white to off-white lyophilised powder, sealed with a flip-off cap over a crimped stopper, in the net quantity stated on the label: 5 mg. There is no carrier, mannitol or other excipient unless the batch certificate says otherwise. The batch number is printed on the label and matches the certificate in our register.
Reading the certificate for a hexarelin batch
Three results matter. Purity by reversed-phase HPLC is reported as the area of the main peak against all peaks and should be above 99% for a six-residue peptide, since a short synthesis has few opportunities for deletion sequences. Identity by LC-MS is reported as the observed mass against the expected mass of about 887 Da; a match within instrument tolerance confirms the sequence including the methylated tryptophan, which distinguishes hexarelin from GHRP-6 on a mass spectrum. Net peptide content gives the milligrams of peptide actually in the vial, as distinct from the nominal fill.
The impurity to watch for is oxidation of the tryptophan residues, which appears as small peaks at plus 16 and plus 32 Da. These should be well below 1% in a fresh lyophilised batch. Our guide to reading a certificate of analysis walks through annotated examples.
Storage and handling
Sealed vials should be kept refrigerated at 2 to 8 °C and protected from light; the tryptophan residues make hexarelin more light-sensitive than most short peptides, so the dark is important. For storage beyond a few months, −20 °C is preferable. The lyophilised powder is stable for well over a year under those conditions. Allow the vial to reach room temperature before opening so that condensation does not form on the powder. Hexarelin dissolves readily in water or dilute buffer. Reconstituted solutions should be prepared fresh or aliquoted and frozen, and kept out of light; the storage and stability guide covers solvents, concentrations and freeze-thaw behaviour.