Neuropeptides
Neurotrophic Peptides in Research: Dihexa, P21, Cerebrolysin, Semax
13 October 2026 · 5 min read
Synaptic plasticity as the starting point
Synaptic plasticity is the ability of connections between neurons to strengthen and weaken in response to activity. Most models that study learning and the formation of memory traces, particularly in the hippocampus, are built around this process. A central question is which factors shape it. In this context, neurotrophic factors and their mimetics, molecules that copy part of their activity in laboratory models, come up more and more often.
The four compounds covered here belong to this group: Dihexa, P21, cerebrolysin and semax. Each one starts from a different point, has a different structure and connects to a different signalling pathway. That makes a side-by-side comparison useful before you plan work with any single reagent. MOLEVIA supplies all four as research reagents (Research Use Only), with purity of 99% or higher by HPLC, mass confirmed by mass spectrometry (MS). For details on our testing, see the quality page.
Dihexa: a ligand of the HGF/c-Met system
Dihexa is an oligopeptide derivative of angiotensin IV. Its molecular mass is 504.7 Da, its molecular formula is C27H44N4O5, and its CAS number is 1401708-83-5. It is studied as a ligand of the HGF/c-Met system. Hepatocyte growth factor (HGF) and its receptor c-Met form one of the best-described signalling axes in nerve cell biology. Work in this area is carried out mainly in vitro and in animal models, where researchers measure the number and growth of synaptic connections.
For a laboratory, a small and well-defined molecule is a practical advantage. It simplifies batch control and makes results easier to compare across experimental series. Dihexa is available in 5 mg and 10 mg vials on its product page.
P21: a CNTF-derived peptide in neurogenesis models
P21 is a peptide derived from CNTF, the ciliary neurotrophic factor. Its adamantyl modification sets it apart from the natural protein and changes its physicochemical properties. Research with P21 focuses on neurogenesis, the formation of new neurons, and on the survival of nerve cells in culture.
CNTF has long been one of the key reference points in neuroprotection research. Smaller peptides derived from it allow researchers to study part of its activity in a simpler system. The 10 mg P21 reagent is listed on its product page.
Cerebrolysin: a mixture with a long research history
Cerebrolysin differs from the other three compounds because it is not a single sequence. It is a mixture of low-molecular-weight peptides and amino acids obtained from pig brain. Its activity in models therefore reflects the whole set of components rather than one defined molecule.
Cerebrolysin has been studied in neurotrophic models and in clinical trials. It is registered as a medicine in some countries, and the literature covers both preclinical and clinical work. For laboratory work we offer it in 60 mg vials, with details on the cerebrolysin page.
Semax: a heptapeptide from the ACTH(4-10) line
Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro, seven amino acid residues in total. It starts from the ACTH(4-10) fragment, and its Pro-Gly-Pro tail is described in the literature as a feature that increases the stability of the peptide. The molecular mass is 813.9 Da and the CAS number is 80714-61-0.
Semax is registered as a medicine in Russia and has been the subject of clinical research. In the laboratory it is studied in neuroregulation models. The BDNF theme, one of the most widely studied neurotrophic proteins, appears often in the literature on this peptide. It is sold in 5 mg, 10 mg and 30 mg vials on the semax page.
Side-by-side comparison
| Feature | Dihexa | P21 | Cerebrolysin | Semax |
|---|---|---|---|---|
| Origin | angiotensin IV | CNTF | pig brain | ACTH(4-10) fragment |
| Structure | oligopeptide derivative, C27H44N4O5 | peptide with adamantyl modification | mixture of peptides and amino acids | heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro |
| Main research direction | HGF/c-Met pathway | neurogenesis, cell survival | broad neurotrophic activity | neuroregulation, BDNF |
| Status | preclinical research | preclinical research | clinically studied, registered in some countries | clinically studied, registered in Russia |
| Form | lyophilized | lyophilized | lyophilized | lyophilized |
| Variants | 5 mg, 10 mg | 10 mg | 60 mg | 5 mg, 10 mg, 30 mg |
Even within one group, the compounds start from different places. The right choice depends on the research question, not on a general impression.
What the models measure
- Cell cultures: neuron survival and neurite growth, mainly in vitro.
- Hippocampal slices: long-term potentiation (LTP), a classic test of synaptic plasticity.
- Animal models: changes in synaptic connections and results in learning tests.
- Analytics: MS confirms identity and HPLC measures purity.
Working with lyophilized material
Store lyophilized reagents as stated on the product sheet, cold, away from light and moisture. A stable lyophilized form lets you plan a series of experiments in advance and link every batch to your own records.
Why order from MOLEVIA
- Purity of 99% or higher (HPLC) and mass confirmed by MS for every compound.
- Same-day dispatch for orders placed by 14:00 on business days.
- InPost parcel locker delivery in Poland on the next business day.
- DPD delivery across Europe in 2-4 business days, to 29 countries.
- Free delivery from 75 EUR, 65 GBP, 80 USD.
- Quantity discounts applied automatically: 5% off for 2 units, 10% for 3 and 15% for 5.
- A free 10 ml vial of bacteriostatic water with orders of 50 EUR (40 GBP, 55 USD) or more that include a peptide vial.
- Pay online by card, Apple Pay, Google Pay or BLIK (PLN only).
You can also browse our neuropeptides category, where we have grouped every compound from this family.
Key takeaways
- Dihexa, P21, cerebrolysin and semax belong to the family of neuropeptides and their mimetics studied in synaptic plasticity models.
- Dihexa acts on the HGF/c-Met pathway, while P21 is a CNTF derivative focused on neurogenesis.
- Cerebrolysin is a peptide mixture, and semax derives from the ACTH(4-10) fragment.
- Cerebrolysin and semax have clinical research behind them and are registered in some countries, while Dihexa and P21 remain at the preclinical stage.
- Each compound needs its own research plan.
- All products are research reagents for laboratory use, shipped within Poland and to 29 European countries.