The GHRP family: GHRP-2, GHRP-6 and Hexarelin side by side

One scaffold, three products

GHRP-2, GHRP-6 and Hexarelin are short synthetic peptides developed from the same structural idea, and they are routinely stocked side by side. They are close relatives — close enough that the differences between them are a residue or a methyl group, and close enough that a catalogue listing alone is weak identification.

Read the sequences against each other. Hexarelin is GHRP-6 with a methyl group added to one tryptophan — a difference of about 14 mass units. GHRP-2 replaces the histidine and one tryptophan with D-alanine and a naphthylalanine. All three end in lysine with a C-terminal amide.

Why the formula matters more than the mass

A 14-unit difference between Hexarelin and GHRP-6 is real and resolvable, but it is small enough that a rounded figure, a different salt form, or a report that does not state which it describes can obscure it. For a family this closely spaced, three habits are worth keeping:

• Read the stated molecular formula alongside the mass. A methyl group shows in a formula unambiguously; it can disappear into rounding in a mass.
• Check the compound name on the report matches the listing. A certificate for one family member does not describe another, however close the figures.
• Expect D-residues, and know what they hide. All three sequences contain D-configured residues, which have identical mass to their L counterparts. A mass result cannot detect the wrong stereoisomer; the chromatogram can, because diastereomers usually separate. This is the same limitation described in detail under Ipamorelin.

What the reports should show

All three are six-residue syntheses — short, so purity figures are typically high and a low one is informative. All three carry a C-terminal amide, so material left as the free acid is a plausible impurity roughly one mass unit heavier and chromatographically separable. None contains methionine or cysteine, so oxidation is not the primary degradation route, though the tryptophan residues in GHRP-6 and Hexarelin are light-sensitive and can degrade by other paths.

See how to read an HPLC chromatogram for where each of those species appears on the plot.

Storage of the lyophilized solid

All three are supplied as freeze-dried solids and governed by temperature and moisture. The tryptophan-containing members are additionally light-sensitive, so opaque storage is doing real work for GHRP-6 and Hexarelin rather than being generic advice.

Stability is a documented property rather than an assumed one: a laboratory establishes it by holding material under defined conditions and re-analysing at intervals. Where a retest date is stated, the question worth asking is what data supports it. See storing lyophilized research materials.

Scope of this documentation

This page concerns material identification and analytical documentation for laboratory research. It does not recommend personal, human, clinical, therapeutic or veterinary applications. Published research findings do not establish the properties of Arctic stock; use the applicable lot record and its stated methods and limitations.

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