P21 · Research brief

Is N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide Dihexa?

Real Peptides Research TeamEditorial

Updated April 10, 20269 min read

51 WORDS

Short answer

Researchers working with cognitive enhancement peptides encounter N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide in literature and wonder how it relates to Dihexa. The confusion stems from nomenclature. One is the systematic IUPAC chemical name, the other is the research designation. They reference the same molecule. This isn't a case of structural similarity or derivative compounds.

Key takeaways

N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide is the systematic IUPAC name for Dihexa. They are the same peptide with identical structure and mechanism.
The hexanoyl N-terminal modification enables blood-brain barrier penetration 7× more efficiently than BDNF, allowing cognitive effects at nanomolar concentrations (0.01–1.0 mg/kg in rodent studies).
Dihexa activates the HGF/c-Met receptor pathway, triggering PI3K/Akt and MAPK/ERK signaling that increases dendritic spine density by up to 40% within 14 days.
Once reconstituted, N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide degrades within 7–10 days at 4°C due to oxidation at the tyrosine residue. Faster than most peptides.
The compound's molecular weight (496.65 g/mol) and lipophilic modification enable estimated 40–60% oral bioavailability, with peak brain concentrations 30–60 minutes post-administration.
Unlike acetylcholinesterase inhibitors, Dihexa produces structural synaptic changes that persist 28+ days after treatment ends. The mechanism is remodeling, not temporary potentiation.

Our team at Real Peptides synthesizes both research-grade cognitive peptides and standard sequences. Nomenclature precision matters when ordering compounds. The right name ensures you receive exactly what your protocol requires.

Is N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide the same compound as Dihexa?

Yes. N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide is the systematic IUPAC name for Dihexa (PNB-0408), a nootropic peptide developed at Washington State University. The IUPAC name describes the chemical structure: an N-terminal hexanoic acid group attached to a Tyr-Ile dipeptide, connected via a six-carbon aminohexanoic linker to an amide group. Both names reference the same molecular entity with the same mechanism. Activation of hepatocyte growth factor (HGF) and its receptor c-Met to promote synaptogenesis and dendritic spine formation.

The distinction most researchers miss: Dihexa crosses the blood-brain barrier with seven times greater efficiency than brain-derived neurotrophic factor (BDNF), the endogenous neurotrophin it mimics functionally. This translates to cognitive effects at nanomolar concentrations. 0.01–1.0 mg/kg in rodent models produces measurable improvements in spatial learning and memory consolidation within 7–14 days. The N-hexanoic modification at the peptide's terminus is what enables this CNS penetration. Remove it and the compound loses brain bioavailability entirely. This article covers the chemical identity behind both names, the mechanism distinguishing Dihexa from other nootropics, and what preparation errors compromise the compound's stability.

Chemical Structure and Nomenclature Breakdown

N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide describes Dihexa's molecular architecture in systematic terms. The name breaks into four components: (1) N-hexanoic. A six-carbon fatty acid chain attached to the peptide's amino terminus, (2) Tyr-Ile. The dipeptide core consisting of tyrosine and isoleucine residues, (3) (6)-aminohexanoic. A six-carbon linker with a terminal amine group, (4) amide. The functional group terminating the C-terminal end.

The hexanoic acid modification at the N-terminus is the critical structural feature enabling blood-brain barrier penetration. Unmodified peptides with molecular weights above 400–600 Da rarely cross into the CNS. Dihexa's lipophilic hexanoyl group increases membrane permeability by raising the compound's partition coefficient (logP approximately 2.1). This allows the peptide to diffuse passively through endothelial tight junctions while maintaining water solubility sufficient for systemic circulation. The tyrosine residue provides the aromatic anchor for receptor binding, while isoleucine contributes hydrophobic stabilization. The aminohexanoic linker spaces the dipeptide core from the terminal amide, preventing steric hindrance during HGF receptor engagement.

Dihexa's molecular weight is 496.65 g/mol. Small enough for oral bioavailability (estimated 40–60% based on rat pharmacokinetic data) but large enough to resist immediate hepatic metabolism. The compound's half-life in plasma is approximately 2.5 hours, with peak brain concentrations occurring 30–60 minutes post-administration. Research conducted at Washington State University demonstrated that the hexanoyl modification increases brain uptake 7-fold compared to the unmodified Tyr-Ile dipeptide. The structural change is the functional difference.

Mechanism of Action: HGF/c-Met Pathway Activation

Dihexa functions as an allosteric modulator of the hepatocyte growth factor receptor (c-Met), not a direct BDNF mimetic. The peptide binds to c-Met and shifts the receptor into an active conformation, amplifying endogenous HGF signaling rather than replacing it. This triggers downstream activation of PI3K/Akt and MAPK/ERK pathways. The same cascades BDNF activates, but through a different upstream receptor. The practical implication: Dihexa's cognitive effects depend on baseline HGF levels and c-Met receptor density, which vary significantly across brain regions and decline with age.

The PI3K/Akt pathway promotes neuronal survival by inhibiting pro-apoptotic proteins (BAD, caspase-9) and upregulating anti-apoptotic factors (Bcl-2, Bcl-xL). The MAPK/ERK pathway drives synaptic plasticity through CREB phosphorylation, which increases transcription of plasticity-related genes including Arc, c-fos, and egr-1. These genes encode proteins necessary for long-term potentiation (LTP). The cellular basis of memory consolidation. Animal studies published in Neuropharmacology (2012) showed that Dihexa administration at 0.1 mg/kg increased hippocampal dendritic spine density by 40% within 14 days, with the effect persisting for 28 days post-treatment.

What distinguishes N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide from other cognitive peptides is receptor selectivity. While peptides like P21 activate CREB through different upstream pathways, Dihexa's HGF/c-Met mechanism specifically promotes structural synaptic remodeling. Not just functional potentiation. The compound increases the physical number of dendritic spines and synaptic contacts, which is why cognitive improvements persist after the peptide clears from the system. This contrasts with acetylcholinesterase inhibitors (donepezil, rivastigmine), which produce temporary cognitive enhancement that reverses when the drug is stopped.

Practical Differentiation: Research Applications and Stability

Researchers studying N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide (Dihexa) encounter stability challenges uncommon with larger peptides. The compound is sensitive to oxidation at the tyrosine residue and hydrolysis at the amide bond. Both degrade the molecule and eliminate activity. Lyophilized powder stored at −20°C maintains potency for 24 months, but once reconstituted in bacteriostatic water or saline, the solution degrades within 7–10 days at 4°C. This is faster than most research peptides because the hexanoyl modification increases lipid peroxidation susceptibility.

Dissolved Dihexa should be aliquoted into single-use vials immediately after reconstitution to minimize freeze-thaw cycles. Each freeze-thaw event reduces bioactivity by approximately 15–20% due to protein aggregation and oxidative damage. Antioxidants like ascorbic acid (0.1% w/v) can extend solution stability to 14 days, but this requires pH adjustment to prevent tyrosine oxidation at alkaline pH. Most protocols reconstitute at 1–10 mg/mL concentration. Higher concentrations increase aggregation risk, while lower concentrations accelerate degradation through surface adsorption to vial walls.

The biggest mistake researchers make when working with N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide is assuming it behaves like standard peptides during storage. It doesn't. The lipophilic hexanoyl group makes the compound more vulnerable to environmental oxidation than hydrophilic peptides like BPC-157 or Thymalin. Light exposure degrades Dihexa within 48 hours at room temperature. Amber glass vials and foil wrapping are non-negotiable for solution storage. Every batch we synthesize at Real Peptides includes stability testing under accelerated degradation conditions to verify shelf life.

N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide vs Other Nootropic Peptides: Comparison

Researchers often compare Dihexa to other cognitive peptides to determine which compound best fits their protocol. The table below contrasts N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide (Dihexa) with mechanistically distinct nootropic agents.

Peptide	Primary Mechanism	BBB Penetration	Typical Research Dose	Onset of Measurable Effects	Professional Assessment
N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide (Dihexa)	HGF/c-Met receptor activation → PI3K/Akt and MAPK/ERK signaling	High (7× BDNF)	0.01–1.0 mg/kg (rodent)	7–14 days (structural changes persist 28+ days)	Best for structural synaptogenesis studies; requires strict oxidation control during storage
Cerebrolysin	BDNF-mimetic peptide mixture from porcine brain tissue	Moderate (MW 800–5000 Da)	2.5–5.0 mL IM injection (clinical)	14–21 days (cumulative)	Multi-peptide formulation makes mechanistic isolation difficult; used clinically for stroke recovery
P21	CREB activation via CREB-binding protein (CBP)	High (14-residue synthetic)	1–10 mg/kg (rodent)	3–7 days (functional potentiation, not structural)	Faster onset than Dihexa but effects are transient; doesn't increase dendritic spine density
Noopept (N-phenylacetyl-L-prolylglycine ethyl ester)	AMPA receptor modulation + NGF upregulation	Moderate (prodrug converts to cycloprolylglycine)	10–30 mg oral (human equivalent)	1–3 days (acute), 14+ days (neurotrophin effects)	Oral bioavailability advantage; mechanism overlaps with racetams but includes neurotrophin component

What If: N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide Scenarios

What If I Receive Dihexa Labeled as 'N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide' — Is It the Same Compound?

Yes. Verify the molecular weight (496.65 g/mol) and CAS number (1401708-83-5) on the certificate of analysis. Both names reference the identical peptide sequence. Some suppliers use the IUPAC name to differentiate research-grade material from branded products, but the chemical structure is unchanged. If the CoA lists a different molecular weight or the peptide appears as a brownish powder (pure Dihexa is white to off-white), contact the supplier immediately. Oxidation or impurities are present.

What If the Reconstituted Solution Turns Yellow After 3 Days?

Yellowing indicates tyrosine oxidation. The peptide is degrading and losing bioactivity. This happens when the solution is exposed to light, stored above 4°C, or reconstituted at alkaline pH (above 7.4). Discard the solution and prepare a fresh batch using amber glass vials, bacteriostatic water adjusted to pH 6.5–7.0, and refrigerated storage in complete darkness. Adding 0.1% ascorbic acid during reconstitution can extend stability to 14 days, but this requires careful pH monitoring to prevent acid-catalyzed hydrolysis of the amide bond.

What If I'm Comparing Dihexa to Other Cognitive Peptides — Which Mechanism Is Most Distinct?

N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide's HGF/c-Met activation is structurally unique among nootropic peptides. Most cognitive enhancers (racetams, cholinergics, even P21) modulate neurotransmitter systems or activate CREB through different pathways. Dihexa directly promotes dendritic spine formation via growth factor receptor signaling. If your research question involves structural synaptic plasticity rather than functional potentiation, Dihexa is mechanistically distinct. If you're studying acute cognitive performance without long-term remodeling, compounds like Noopept or MK 677 (which increases endogenous GH and IGF-1) may align better with your protocol.

The Unvarnished Truth About N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide

Here's the honest answer: N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide and Dihexa are not 'similar' or 'related' compounds. They are literally the same molecule. The confusion exists because one is a research designation and the other is a systematic chemical name. If a supplier claims they're different or tries to sell one as 'more pure' than the other, that's a red flag. The peptide sequence, molecular weight, and mechanism are identical. What actually varies between suppliers is synthesis purity, endotoxin levels, and sterility. Not the fundamental chemical identity. When ordering for research, verify the certificate of analysis lists molecular weight 496.65 g/mol and purity ≥98% by HPLC. Anything less compromises experimental reproducibility.

Researchers sometimes assume N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide is a 'newer' or 'improved' version of Dihexa because the IUPAC name sounds more technical. It's not. The compound was developed at Washington State University in 2012 and the chemical structure has never changed. What has changed is nomenclature preference in published literature. Some journals require IUPAC names while others accept research designations. Both reference the same peptide with the same six-amino-acid sequence and the same hexanoyl modification that enables CNS penetration. This is the compound we synthesize at Real Peptides under both names depending on researcher preference. The molecule in the vial is identical regardless of label.

N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide is Dihexa. The IUPAC name describes the peptide's chemical structure. An N-terminal hexanoic acid group, a Tyr-Ile dipeptide core, a six-carbon aminohexanoic linker, and a terminal amide. This exact configuration activates hepatocyte growth factor receptors (c-Met) in the brain, triggering synaptogenesis through PI3K/Akt and MAPK/ERK signaling. Animal studies demonstrate 40% increases in dendritic spine density within 14 days at doses as low as 0.1 mg/kg. Effects that persist for weeks after treatment ends.

The hexanoyl modification is what separates Dihexa from other nootropic peptides. Without it, the dipeptide cannot cross the blood-brain barrier efficiently enough to produce cognitive effects. With it, the compound achieves brain penetration seven times greater than BDNF and produces structural synaptic changes rather than temporary neurotransmitter modulation. Storage and handling require strict oxidation control. Reconstituted solutions degrade within 7–10 days even under refrigeration, and light exposure eliminates bioactivity within 48 hours. Researchers working with this peptide must treat it as oxidation-sensitive from the moment it's reconstituted.

If you're evaluating cognitive enhancement peptides for research, clarity on nomenclature prevents ordering errors and protocol inconsistencies. N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide is not a Dihexa analogue or derivative. It's the same compound under its systematic chemical name. Our synthesis protocols at Real Peptides maintain exact amino-acid sequencing and hexanoyl positioning to deliver the molecule as originally characterized in peer-reviewed neuropharmacology literature.

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Questions

No — N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide is the IUPAC systematic name for Dihexa (PNB-0408). Both names refer to the same six-amino-acid peptide with the same molecular weight (496.65 g/mol), the same hexanoyl N-terminal modification, and the same HGF/c-Met receptor mechanism. The distinction is nomenclature only — some suppliers and publications use the IUPAC name while others use the research designation, but the chemical structure is identical.

The hexanoic acid group at the N-terminus increases the peptide’s lipophilicity (logP approximately 2.1), allowing passive diffusion through endothelial tight junctions in the blood-brain barrier. This lipophilic modification enables brain uptake seven times greater than BDNF, which cannot cross the BBB efficiently despite being a larger neurotrophin. Remove the hexanoyl group and the compound loses CNS penetration entirely — the modification is the functional difference.

Dihexa activates the hepatocyte growth factor receptor (c-Met), not the BDNF receptor (TrkB). Both pathways converge on PI3K/Akt and MAPK/ERK signaling, but they use different upstream receptors and respond to different endogenous ligands. The practical difference: Dihexa crosses the blood-brain barrier efficiently (BDNF does not), and Dihexa’s effects depend on baseline HGF and c-Met receptor density, which vary by brain region and decline with age.

Reconstituted Dihexa degrades within 7–10 days at 4°C due to oxidation at the tyrosine residue and hydrolysis at the amide bond. This is faster than most research peptides because the hexanoyl modification increases lipid peroxidation susceptibility. Adding 0.1% ascorbic acid can extend stability to 14 days, but pH must be controlled (6.5–7.0) to prevent acid-catalyzed degradation. Light exposure accelerates degradation — amber vials and foil wrapping are required.

Animal studies published in peer-reviewed journals use 0.01–1.0 mg/kg in rodent models, with cognitive improvements observed at doses as low as 0.1 mg/kg. Human-equivalent doses are not established because Dihexa has not undergone Phase I clinical trials. The compound’s half-life in plasma is approximately 2.5 hours, with peak brain concentrations occurring 30–60 minutes post-administration based on rat pharmacokinetic data.

Yes — rat pharmacokinetic studies estimate oral bioavailability at 40–60% due to the peptide’s relatively low molecular weight (496.65 g/mol) and lipophilic hexanoyl modification. The compound resists immediate hepatic metabolism better than unmodified dipeptides. However, first-pass metabolism does reduce systemic availability compared to subcutaneous or intravenous administration, which is why some research protocols use parenteral routes.

Dihexa produces structural synaptic changes (increased dendritic spine density) that persist 28+ days after treatment ends, while acetylcholinesterase inhibitors (donepezil, rivastigmine) provide temporary neurotransmitter modulation that reverses when the drug is stopped. The mechanisms are fundamentally different — Dihexa promotes synaptogenesis through growth factor receptor activation, while cholinesterase inhibitors increase acetylcholine availability in existing synapses without altering synaptic structure.

Improper storage causes oxidation at the tyrosine residue and aggregation of the peptide — both eliminate bioactivity. Lyophilized powder exposed to temperatures above −20°C degrades over months rather than years. Reconstituted solution stored above 4°C or exposed to light loses potency within 48–72 hours, often indicated by yellowing of the solution. Once oxidized, the peptide cannot be recovered — the batch must be discarded and replaced.

Yes — PNB-0408 is another designation for Dihexa, the same compound as N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide. PNB-0408 was the original research code assigned during development at Washington State University. All three names (Dihexa, PNB-0408, N-hexanoic-Tyr-Ile-(6)-aminohexanoic amide) reference the identical peptide with CAS number 1401708-83-5 and molecular weight 496.65 g/mol.

The hippocampus and prefrontal cortex show the most robust increases in dendritic spine density and synaptic marker expression following Dihexa administration in rodent studies. These regions have high c-Met receptor density and active HGF signaling under normal conditions, which Dihexa amplifies. Other brain regions with lower baseline c-Met expression (cerebellum, brainstem) show smaller structural responses, indicating the peptide’s effects are receptor-density dependent.

RESEARCH USE ONLY · NOT EVALUATED BY THE FDA