Dihexa is a peptidomimetic. Of its four building blocks only two are amino acids — the other two are ordinary fatty-acid chains — and those non-standard parts are the reason the molecule survives long enough to be interesting.
Calling it a peptide is a category error of the same kind covered in 5-amino-1MQ is not a peptide, and it has practical consequences: the handling intuitions and the certificate conventions that apply to peptides do not all transfer. This post covers the structure, where it came from, what the research actually shows, and one gap in this catalogue's own documentation.
What it is made of
The systematic name is N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide. Read left to right, that is four parts:
| Part | What it is | Found in proteins? |
|---|---|---|
| Hexanoic acid | A six-carbon saturated fatty acid, capping the N-terminus | No |
| Tyrosine (Tyr) | Standard amino acid | Yes |
| Isoleucine (Ile) | Standard amino acid | Yes |
| 6-aminohexanoic acid | A six-carbon chain with the amine on the far end, amidated | No |
Two standard residues, two aliphatic chains. The published molecular weight is approximately 562.7 Da.
6-aminohexanoic acid is the unusual one. In a standard amino acid the amine and carboxyl sit on adjacent carbons. Here they are separated by five carbons, which makes it a flexible spacer rather than a residue — it cannot form the backbone geometry a peptidase recognises.
Why the non-peptide parts are the point
A dipeptide of tyrosine and isoleucine would be destroyed almost immediately. Free termini are what peptidases recognise: aminopeptidases attack a free N-terminal amine, carboxypeptidases a free C-terminal carboxyl.
Dihexa has neither. The N-terminus is capped with hexanoic acid; the C-terminus is an amide on a chain that is not a residue. Both recognition points are gone.
This is the same logic the incretin analogues use by a different route. Semaglutide inserts a non-standard Aib residue to stop DPP-4; sermorelin has no such protection and is cleared in minutes as a result. Capping both ends with aliphatic chains is a blunter version of the same idea, and it works because there is so little peptide left to protect.
The aliphatic chains also raise lipophilicity, which is relevant to whether a molecule crosses membranes — a stated design goal in the original work.
Where it came from
Dihexa derives from angiotensin IV, a fragment of the angiotensin system — the same hormonal cascade that regulates blood pressure and is the target of ACE inhibitors and ARBs.
Angiotensin IV is a hexapeptide fragment with activity distinct from angiotensin II's cardiovascular role. Wright and Harding's 2008 review covers the AT4 receptor and the line of reasoning that connected it to memory function.
The development sequence, from Benoist et al. (2011) and McCoy et al. (2013): start with angiotensin IV, truncate it, replace the vulnerable parts with non-standard components, and test what survives. Dihexa is the output of that programme. McCoy and colleagues' 2013 paper is the primary reference for the compound itself.
The proposed mechanism involves hepatocyte growth factor and its receptor c-Met rather than the AT4 receptor directly — the suggestion being that Dihexa potentiates HGF signalling. That mechanism is described in the primary literature and has not been independently established to the degree a settled mechanism would be.
What the evidence actually is
Preclinical. Rodent models of cognitive impairment, plus in-vitro synaptogenesis work. The reported potencies in those models are what attracted attention to the compound.
There are no published human clinical trials. Not few — none. Everything known about Dihexa's biological activity comes from animal and cell work by a small number of groups.
The gap between a rodent cognition model and a human outcome is as wide here as anywhere, and why trial data does not transfer covers why. High potency in a model is a reason to study a compound further, not evidence that it does anything in people.
Handling
Being a peptidomimetic rather than a peptide changes several practical expectations:
| Property | Behaviour |
|---|---|
| Solubility | Less water-soluble than a peptide of similar mass; the two aliphatic chains are hydrophobic |
| Diluent | May need a co-solvent — see DMSO stock solutions for peptides and choosing a peptide diluent |
| Enzymatic stability | High, by design |
| Detection at 214 nm | Weak. Two peptide bonds and one tyrosine; absorbance is low and peaks are small |
| Adsorption | Lipophilic molecules bind plastic readily — why peptides stick to plastic |
The tyrosine is useful analytically: it absorbs at 280 nm, which gives a second detection wavelength that most short peptides do not offer. Quantifying a peptide by A280 covers that method and its assumptions.
A gap worth naming
There is no certificate of analysis published for Dihexa in this catalogue. Every other compound referenced in this article has one, with a lot number, a purity figure, an identity method and an endotoxin result.
That is a documentation gap rather than a statement about the material, and it matters because the whole basis on which this catalogue asks to be judged is that the lot certificate is published before the vial is listed. A product without one is inconsistent with that, and the right response is to close the gap rather than explain it away.
Until it is closed, the molecular weight quoted above is a literature figure and has not been confirmed against a certificate for this material. How to verify a certificate of analysis covers what a certificate establishes; none of it is available here.
Regulatory position
Dihexa is not an approved drug in any jurisdiction. It has no established safety profile in humans and is supplied for laboratory research only — what "research use only" means covers the limits of that designation.
Frequently asked questions
Is Dihexa a peptide?
No. Two of its four components are not amino acids. It is a peptidomimetic — a molecule designed to imitate a peptide's interactions without a peptide's backbone.
What does the "di" in Dihexa refer to?
The two hexanoic components: hexanoic acid at one end and 6-aminohexanoic acid at the other. Not two peptides.
Why is it described as so much more potent than angiotensin IV?
Reported potency differences in the primary literature come from cell and animal assays. Those are model-specific measurements, not a general property, and they do not transfer to any human context.
Does it cross the blood-brain barrier?
Increased lipophilicity from the two aliphatic chains was a design goal, and the primary literature discusses CNS exposure in animals. That is an animal finding, not an established human property.
Why is there no certificate?
The catalogue does not currently publish one for this compound. That is a gap in documentation and a question to put to the supplier before using the material.
Can I treat it like a peptide for storage?
Broadly, but expect lower aqueous solubility and better enzymatic stability. The usual lyophilized storage guidance in how to store peptide vials applies.
References
- McCoy AT, Benoist CC, Wright JW, et al. Evaluation of metabolically stabilized angiotensin IV analogs as procognitive/antidementia agents. Journal of Pharmacology and Experimental Therapeutics 2013;344(1):141-54. doi.org/10.1124/jpet.112.199497
- Benoist CC, Wright JW, Zhu M, et al. Facilitation of hippocampal synaptogenesis and spatial memory by C-terminal truncated Nle1-angiotensin IV analogs. Journal of Pharmacology and Experimental Therapeutics 2011;339(1):35-44. doi.org/10.1124/jpet.111.182733
- Wright JW, Harding JW. The angiotensin AT4 receptor subtype as a target for the treatment of memory dysfunction associated with Alzheimer's disease. Journal of the Renin-Angiotensin-Aldosterone System 2008;9(4):226-37. doi.org/10.1177/1470320308099084
Every product mentioned is sold for laboratory research use only and is not for human or animal use. Nothing on this page describes or recommends use of the material sold here in humans or animals.
