Khavinson Bioregulator Peptides: Sequence Families, Analysis and Format Selection

Bioregulator peptides are the shortest peptides in the catalogue. Most are two to four residues and 291 to 577 g/mol — smaller than many of the small molecules filed under research compounds — and they come from a single Soviet-era research programme at the St Petersburg Institute of Bioregulation and Gerontology led by Vladimir Khavinson. Working with them is unlike working with any other peptide class in the catalogue: the analytical methods that serve a 1,400 Da pentadecapeptide are the wrong methods for a 291 Da dipeptide, the sequences are close enough to one another that a parent-ion mass is weak identity evidence, and the range splits into two branches whose certificates mean completely different things.

This guide covers that structure: the two product branches, the three sequence families that nearly all of the synthetic ones belong to, the analytical and stability consequences of being this small, and how to choose between a defined sequence and a tissue complex. The underlying mechanistic hypothesis and its evidence problem are summarised in the bioregulator glossary entry and are not re-argued here. All of it describes research chemicals for in-vitro and preclinical laboratory work.

Two branches with the same name

The programme produced two generations of material, and both are still sold, which is the single most common source of confusion. The first generation were cytomedines: crude peptide fractions extracted from animal tissue and specified by total peptide content rather than by structure. Thymalin, from thymus, is the surviving example in vial form — its specification states plainly that no single molecular mass and no amino acid sequence apply, because the complex contains multiple peptide species. The retail descendants of that branch are the Cytomax capsules: Cerluten from nervous tissue, Endoluten from pineal, Sigumir from cartilage, Visoluten from retina, Ventfort from vascular tissue. Cortexin, a low-molecular-weight cortical polypeptide complex in 10 mg vials, belongs to the same category even though it is filed with the nootropic peptides.

The second generation are defined synthetic sequences, the Cytogen line, and these are ordinary synthetic peptides in every respect that matters analytically: a stated sequence, a molecular formula, a molecular weight, usually a CAS number, and a purity figure from reversed-phase HPLC. Vilon, Livagen, Cardiogen, Cortagen, Bronchogen, Chonluten, Crystagen, Ovagen, Pancragen, Prostamax, Testagen, Cartalax, Pinealon and Epitalon are all in this branch. Several are explicitly described as the defined-sequence counterpart of a tissue preparation — Epitalon for the pineal complex, Cartalax for cartilage, Pancragen as the synthetic analogue of Suprefort — which is a relationship worth knowing but not one that licenses treating the two as interchangeable reagents.

The practical consequence is about documentation. A synthetic bioregulator can carry a purity figure because purity is a meaningful quantity for a single compound. A tissue complex cannot: there is nothing for 99% to be 99% of. What its certificate can report is identity and fraction profile per lot, total peptide content, molecular-weight range — characteristically below about 10 kDa — and source species and tissue traceability. If a supplier prints an HPLC purity percentage on a tissue-extract complex, that number is describing something other than what the label implies, and the right response is to ask which.

Three sequence families, one varying residue

Lay the synthetic sequences out together and the design grammar is immediate. Nearly all of them are a short acidic core with one residue swapped at the C-terminus, and that final residue is what carries the tissue label.

The Ala-Glu-Asp family

Cartalax is the bare core: H-Ala-Glu-Asp-OH, 333.30 g/mol, the cartilage-associated tripeptide. Add a glycine and it becomes Epitalon, Ala-Glu-Asp-Gly at 390.35 g/mol, the pineal tetrapeptide. Add a proline instead and it is Cortagen, Ala-Glu-Asp-Pro at 430.41 g/mol, associated with cerebral cortex. Arginine gives Cardiogen, Ala-Glu-Asp-Arg at 489.48 g/mol, heart. Leucine gives Bronchogen, Ala-Glu-Asp-Leu at 446.46 g/mol, bronchial tissue. Five tissue assignments, one shared three-residue backbone, and a single position of variation.

The Lys-Glu-Asp family

Vilon is the two-residue ancestor, Lys-Glu at 291.30 g/mol, associated with thymus. Extended to Lys-Glu-Asp and then capped, it generates Testagen (KEDG, 447.44 g/mol, gonadal), Livagen (KEDA, 461.47 g/mol, liver), Prostamax (KEDP, 487.51 g/mol, prostate) and Pancragen (KEDW, approximately 576.6 g/mol, pancreatic). The lysine is what distinguishes this family functionally as well as structurally: it is the only basic residue in the series, so the KED peptides are zwitterionic while the rest are net anionic, and that single difference changes how they behave on an ion-exchange column and how they adsorb to glass.

The Glu-Asp family

The shortest core of the three. Chonluten is Glu-Asp-Gly, 319.27 g/mol, bronchopulmonary and mucosal. Pinealon is Glu-Asp-Arg, 418.41 g/mol, brain and pineal. Crystagen is Glu-Asp-Pro, 359.33 g/mol, immune. Ovagen is Glu-Asp-Leu, 375.38 g/mol, hepatic and reproductive depending on which paper you are reading — its own specification flags that ambiguity and asks you to verify against the cited study, which is the correct handling of a disputed tissue assignment. Thymogen sits outside all three families: H-Glu-Trp-OH at 333.34 g/mol is the only one containing a tryptophan, and therefore the only one in the series with a meaningful photodegradation and indole-oxidation liability.

Why identity is harder here than purity

Two facts about the lists above combine badly. The first is that several of these peptides are literal subsequences of each other: Crystagen (Glu-Asp-Pro) is the C-terminal three residues of Cortagen (Ala-Glu-Asp-Pro), and Cartalax (Ala-Glu-Asp) is the N-terminal three of Epitalon (Ala-Glu-Asp-Gly). The second is that the masses cluster tightly, and in at least one case collide: Cartalax at 333.30 g/mol and Thymogen at 333.34 g/mol are indistinguishable on any instrument reporting to the nearest mass unit, despite sharing not a single residue in common.

A parent-ion mass is therefore not an identity test for this class, however reassuring it looks on a certificate. What establishes identity is MS/MS fragmentation showing the expected b- and y-ion series, or amino-acid analysis after hydrolysis, or co-injection against a reference standard on a method that actually separates the family. Ask which one was run. On a 1,400 Da pentadecapeptide a matching parent mass is strong evidence because the search space is enormous; on a tripeptide drawn from a catalogue of twelve near-isomeric tripeptides it is close to no evidence at all.

Reversed-phase chromatography is the wrong first method

These peptides are small, highly polar and multiply charged. On a standard C18 column with a water–acetonitrile gradient they have almost nothing to retain them: they elute at or near the void volume, where they co-elute with salts, buffer components and injection artefacts, and where small retention differences between family members vanish entirely. A purity figure generated that way is not wrong so much as uninformative.

The appropriate methods are the ones that exploit polarity and charge rather than hydrophobicity: hydrophilic-interaction chromatography, ion-pairing reversed phase with a stronger pairing agent, or ion-exchange. For the net-anionic families, anion exchange separates on exactly the property that distinguishes them. If a certificate for a tripeptide bioregulator reports a C18 retention time in the first two minutes of a twenty-minute gradient, that is the tell, and the orthogonal method is what to request. The general principles are in the HPLC purity guide; the point specific to this class is that method choice, not percentage, is the number that matters.

Stability: two bonds to be careful with

Short acidic peptides are chemically robust compared with the oxidation-prone sequences elsewhere in the catalogue — with no methionine, cysteine or tryptophan in any of them except Thymogen, the usual oxidative routes are simply unavailable. Two backbone liabilities remain, and both are determined by which residue follows the aspartate.

Aspartyl-glycine is the canonical succinimide site. Asp-Gly cyclises to a succinimide intermediate that opens to give isoaspartate, a rearranged backbone with the same molecular mass as the parent, and it does so fastest at neutral to mildly alkaline pH. Epitalon (AEDG), Chonluten (EDG) and Testagen (KEDG) all carry that motif. Because the isoaspartyl product is isobaric with the intended peptide, a mass check will not see it; the detection methods are a chromatographic separation sensitive enough to resolve the two, or an isoaspartate-specific assay. This is the strongest argument for ordering these peptides as powder and reconstituting fresh rather than holding aqueous stock for weeks.

Aspartyl-proline is the most acid-labile peptide bond in common sequences, hydrolysing far faster than any other backbone amide under mildly acidic conditions. Cortagen (AEDP), Crystagen (EDP) and Prostamax (KEDP) all contain it. Several of these peptides also give acidic solutions when reconstituted — Cartalax's specification notes this explicitly — so an Asp-Pro bioregulator dissolved in unbuffered water is sitting at the pH that cleaves it. Buffering to neutrality before extended storage, and avoiding acidic mobile phases for anything but a short analytical run, is the handling change that follows.

N-Acetyl Epitalon Amidate exists in the catalogue for this reason: capping the N-terminus with an acetyl group and converting the C-terminal carboxyl to a primary amide removes the free termini that exopeptidases require, taking Ala-Glu-Asp-Gly from 390.35 to approximately 431.4 g/mol. It is the right comparator for any study whose variable is degradation rate rather than sequence, and the general logic of terminal protection is set out in the peptide stability guide.

Choosing between a sequence, a complex and a format

Choose a defined synthetic sequence for anything quantitative

If the experiment needs a stated molar concentration, a reproducible reagent across lots, or a result another group can replicate, the synthetic Cytogen peptides are the only option that supports it. They have a formula, a mass, a sequence and a purity figure, which means molarity is calculable and the material can be characterised independently. The 20 mg vials across this range — Cardiogen, Cortagen, Chonluten, Crystagen, Ovagen, Pancragen, Prostamax, Testagen, Vilon, Livagen, Cartalax and Pinealon all ship at that size — are deliberately uniform, which makes a parallel panel across tissue assignments straightforward to set up at matched concentration.

Choose a tissue complex only when the preparation is the question

The Cytomax capsules and the cytomedine vials are the historical articles. If the research question is specifically about those preparations — replicating an older study, comparing a complex against its defined-sequence counterpart, or characterising what is actually in a tissue fraction — then Thymalin, Cortexin, Cerluten, Endoluten, Sigumir and Visoluten are the correct materials and no synthetic peptide substitutes for them. For any other purpose they introduce an uncontrolled variable: a mixture of unspecified composition, from an animal source, at a peptide content stated per lot.

Format follows the question, not convenience

The range exists in three formats and they are not equivalent inputs. Lyophilized vials let you set concentration and are the only format suited to cell culture or any dose–response design. Capsules carry a fixed content with no preparation step, which makes them the format for studies about the oral route itself — relevant because di- and tripeptides are substrates for the intestinal PEPT1 transporter, so the oral prospects for this class are genuinely different from those of a 4,000 Da incretin analogue; the trade-offs are covered in the oral peptides guide. Pre-mixed sprays exist for two members of the range, Epitalon and Pinealon, both comfortably under the molecular-weight ceiling that limits nasal absorption. Epitalon alone spans all three, as a vial, as 10 mg capsules and as a metered spray, which makes it the only member of the class that supports a clean three-way format comparison on one molecule.

Regulatory framing

Bioregulator peptides are supplied as research chemicals for in-vitro and preclinical laboratory work only. None is approved as a drug in the United States or the European Union. The tissue-complex preparations have a regulatory history in the Russian Federation that attaches to specific pharmaceutical or supplement articles manufactured there and does not transfer to research-grade material supplied elsewhere. The proposed mechanism for this class — direct peptide interaction with promoter sequences in double-stranded DNA rather than signalling at a cell-surface receptor — remains a hypothesis supported largely by the originating group's own publications, with limited independent replication. Describe it as reported, never as established, and treat the tissue labels as names rather than as demonstrated tissue selectivity.