RP-HPLC raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-01-16. Anything still debated is marked as such rather than presented as settled.
Laboratory-grade epitalon is typically supplied as a lyophilized powder. Purity is commonly assessed with reverse-phase high-performance liquid chromatography, often paired with mass spectrometry to confirm molecular identity. Amino acid analysis and peptide mapping can provide additional confirmation of sequence. Certificates of analysis for research materials frequently report purity above 95 percent, although the methods behind such figures vary between suppliers. The absence of a pharmacopeial monograph means that no single standardized assay defines the compound, so reported results depend on the analytical protocol chosen.
Storage recommendations center on limiting moisture, heat, and light. The dry powder is generally kept at minus 20 degrees Celsius, and some suppliers recommend minus 80 degrees for long-term archival. Once dissolved, solutions are usually aliquoted and frozen to avoid repeated freeze-thaw cycles, which can promote aggregation or degradation. Aqueous stability depends on pH and concentration, and buffered saline is often preferred over plain water for biological work. Stability data specific to epitalon remain limited, so general peptide-handling practices are applied by analogy rather than from product-specific validation.
Epitalon is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and its calculated monoisotopic mass is approximately 390.35 daltons. The compound does not occur naturally as a free peptide; it is produced by solid-phase peptide synthesis. Because it contains two acidic residues and no basic residues, the neutral form carries a net negative charge at physiological pH. This charge profile influences how the peptide behaves in solution and during chromatographic analysis.
Short peptides such as AEDG are normally supplied as a freeze-dried solid and are kept dry, cold, and shielded from light. Holding at minus twenty degrees Celsius is common for the long term, while a refrigerator suffices for brief periods before use. The material takes up moisture to some degree, so containers should stay sealed and be allowed to reach room temperature before opening, which limits condensation on the contents. Repeated warming and cooling of a single container is discouraged because it admits water and can lower the amount of intact peptide.
Dissolution is usually performed in water or a suitable aqueous buffer, and the resulting liquid is divided into single-use portions before freezing. Freeze-thaw cycling is a recognised source of loss for short peptides, since each cycle can encourage aggregation or adsorption onto container walls. Working solutions are generally kept cold and used within a short window, although published stability data specific to epitalon are thin. Containers should be marked with concentration and date, and solutions examined for cloudiness before use.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C14H22N4O9 | Free acid form of the tetrapeptide |
| Molecular mass | About 390.35 Da | Calculated monoisotopic value |
| Appearance | White to off-white powder | Typical lyophilized presentation |
| Solubility | Soluble in water | Also dissolves in buffered saline |
| Storage temperature | Minus 20 degrees Celsius | Dry, dark conditions; avoid repeated thawing |
Epitalon is a synthetic tetrapeptide with the sequence alanine-glutamate-aspartate-glycine, commonly abbreviated AEDG. It was designed at the St. Petersburg Institute of Bioregulation and Gerontology as a short, chemically defined analogue of epithalamin, a fraction obtained from bovine pineal tissue. Small peptide bioregulators of this type formed a long-running line of work there from the 1980s onward. Because the molecule is produced by solid-phase synthesis rather than extraction, its composition is exact and its purity can be measured directly.
The most frequently cited proposed action is induction of telomerase, the enzyme that adds repeat sequences to chromosome ends. Cell-culture work from the originating group reported higher telomerase reverse transcriptase expression and measurable telomere elongation in human somatic cells after exposure. How a four-residue peptide would reach nuclear gene regulation is not established, and no cell-surface receptor or uptake route has been identified. Additional reports describe changes in melatonin secretion, antioxidant enzyme activity and lipid peroxidation in aged animals, but these findings remain mechanistically unconnected to the telomerase observation.
Published evidence comes mainly from Russian-language journals and from a single research group, with small sample sizes and limited independent replication. A few laboratories outside that group have examined related peptides and reported weaker or absent telomerase effects, so the central claim is best described as contested rather than settled. Rodent studies report modest changes in some ageing markers and in survival, but designs vary and control conditions are often sparse. No large randomised trial in humans has been published, and long-term safety data in healthy populations are correspondingly thin.
Solubility is high in water, phosphate-buffered saline and normal saline, a pattern that follows from the two acidic residues in the chain. The peptide dissolves poorly in non-polar solvents such as hexane or chloroform. Stock solutions are often prepared in water first and then diluted into the buffer of interest. Because the molecule is small and hydrophilic, filtration through a low-protein-binding membrane is usually straightforward, and visible particulates are uncommon in freshly made solutions.
Identity and purity are established with reversed-phase high-performance liquid chromatography and mass spectrometry. The chromatogram shows the main peak and any truncated or oxidised by-products, while the mass spectrum confirms the expected 390 dalton mass. Amino acid analysis can corroborate composition when a sample's origin is uncertain. Counterion content, particularly residual trifluoroacetate from purification, is frequently reported alongside purity because it shifts the net mass of the solid.
Material supplied for laboratory use is normally a lyophilised white to off-white powder that dissolves readily in water and in isotonic saline. Lyophilised cakes are hygroscopic and should be equilibrated to room temperature before opening to limit condensation on the solid. Solutions are typically prepared at milligram-per-millilitre concentrations and divided into single-use aliquots, because repeated freeze–thaw cycles degrade short peptides. Aqueous solutions are far less stable than the dry powder, and identity is usually verified by mass spectrometry alongside purity estimation from reversed-phase high-performance liquid chromatography.
Epitalon is a synthetic linear tetrapeptide with the sequence alanine–glutamate–aspartate–glycine, abbreviated AEDG. Its molecular formula is C14H22N4O9 and the calculated mass is approximately 390.35 g/mol. The compound is made by solid-phase peptide synthesis rather than extracted from tissue, although early work described it as a short fragment of a peptide fraction obtained from bovine pineal extract. In the research literature the spelling epitalon and the variant epithalone both appear, while AEDG is the standard code used in peptide nomenclature.
Several names circulate for the same molecule, including epitalon, epithalone, epithalamin tetrapeptide, and the sequence code AEDG. A CAS registry number, 307297-39-8, is commonly cited for it, though catalogue entries should be checked against supplier documentation because mislabelled records occur. In its usual form the peptide carries free amino and carboxyl termini and is neither glycosylated nor lipidated. Researchers distinguish the defined tetrapeptide from epithalamin itself, a crude pineal preparation containing many peptides that is not chemically characterised.
Reversed-phase high-performance liquid chromatography is the standard approach for assessing purity, usually with ultraviolet detection near 214 nm, where the peptide bond absorbs. Mass spectrometry, most often with electrospray ionization, confirms the molecular mass and helps reveal truncation or deletion byproducts. Amino acid analysis can verify composition, and counterion content is sometimes measured because peptides purified with trifluoroacetic acid retain variable amounts of that salt. Purity figures reported without a stated method and detection wavelength are difficult to interpret.
Material sold for research use varies widely in documented quality. A useful verification package includes a certificate of analysis that states peptide content rather than only net weight, the chromatographic method and column used, and a mass spectrum consistent with the expected mass. Independent testing by a third-party laboratory is occasionally reported. Statements of identity resting only on a supplier label provide little assurance, and the gap between nominal mass and actual peptide content can be substantial once counterions and residual water are counted.
The bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen. The bacteria might outcompete other (pathogenic) soil microbes, e.g., by siderophores, giving a competitive advantage at scavenging for iron. The bacteria might produce compounds antagonistic to other soil microbes, such as phenazine-type antibiotics or hydrogen cyanide. To be specific, certain P. fluorescens isolates produce the secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG), the compound found to be responsible for antiphytopathogenic and biocontrol properties in these strains. The phl gene cluster encodes factors for 2,4-DAPG biosynthesis, regulation, export, and degradation. Eight genes, phlHGFACBDE, are annotated in this cluster and conserved organizationally in 2,4-DAPG-producing strains of P. fluorescens. Of these genes, phlD encodes a type III polyketide synthase, representing the key biosynthetic factor for 2,4-DAPG production. PhlD shows similarity to plant chalcone synthases and has been theorized to originate from horizontal gene transfer. Phylogenetic and genomic analysis, though, has revealed that the entire phl gene cluster is ancestral to P. fluorescens, many strains have lost the capacity, and it exists on different genomic regions among strains. Some experimental evidence supports all of these theories, in certain conditions; a good review of the topic is written by Haas and Defago. Several strains of P. fluorescens, such as Pf-5 and JL3985, have developed a natural resistance to ampicillin and streptomycin.
== Pathophysiology == The cause of the disease is the lack of a fully functional insulin receptor, which has a profound effect during fetal development and thereafter. In one case, it was found (by culturing pancreatic cells) that the receptor produced by the mutant allele is only about 15% as effective as the normal receptor. The beta cells in the pancreas, which make and store insulin and release it on an as-needed basis, are often found to be very large or numerous. The role of insulin in the body is to facilitate the entrance of glucose into the cell. Once insulin binds to the insulin receptors on the cell surface, the insulin receptors will send a signal that will ultimately bring the glucose transporter protein GLUT4 to attach to the cell membrane. Additionally, once insulin is bound to the insulin receptors, it will also initiate several signaling cascades that will promote cell growth and differentiation, protein synthesis, glucose synthesis, and the inhibition of gluconeogenesis through several metabolic pathways. A malfunctioning insulin receptor would thus not be able to properly initiate the signaling cascades for the aforementioned cellular processes. Many of the problems associated with Donohue syndrome may be due to the insulin receptor binding the insulin-like growth factor, regulating the growth of the embryo, in addition to its well-known role in the regulation of blood sugar.
==== Proposed mechanism ==== The mechanism of progesterone protective effects may be the reduction of inflammation that follows brain trauma and hemorrhage. Damage incurred by traumatic brain injury is believed to be caused in part by mass depolarization leading to excitotoxicity. One way in which progesterone helps to alleviate some of this excitotoxicity is by blocking the voltage-dependent calcium channels that trigger neurotransmitter release. It does so by manipulating the signaling pathways of transcription factors involved in this release. Another method for reducing the excitotoxicity is by up-regulating the GABAA, a widespread inhibitory neurotransmitter receptor. Progesterone has also been shown to prevent apoptosis in neurons, a common consequence of brain injury. The hormone does so by inhibiting enzymes involved in the apoptosis pathway specifically concerning the mitochondria, such as activated caspase-3 and cytochrome c. Not only does progesterone help prevent further damage, it has also been shown to aid in neuroregeneration. One of the serious effects of traumatic brain injury includes edema. Animal studies show that progesterone treatment leads to a decrease in edema levels by increasing the concentration of macrophages and microglia sent to the injured tissue. This was observed in the form of reduced leakage from the blood brain barrier in secondary recovery in progesterone treated rats. In addition, progesterone was observed to have antioxidant properties, reducing the concentration of oxygen free radicals faster than without.
Sources: en.wikipedia.org
=== Stereochemistry === Oxprenolol is a chiral compound, the beta blocker is used as a racemate, e. g. a 1:1 mixture of (R)-(+)-oxprenolol and (S)-(–)-oxprenolol. Analytical methods (HPLC) for the separation and quantification of (R)-(+)-oxprenolol and (S)-(–)-oxprenolol in urine and in pharmaceutical formulations have been described in the literature.
Indeed, the AAS mesterolone has been used to improve sperm quality and fertility in men because, apparently unlike other AAS, it shows minimal antigonadotropic effects at typical clinical dosages but activates the AR and thereby supports sperm maturation in the epididymides. However, this use of mesterolone is controversial and its efficacy for such purposes is not fully certain. Although bicalutamide alone would appear to have minimal detrimental effect on testicular spermatogenesis and hence on certain aspects of male fertility, other hormonal agents that bicalutamide may be combined with, including GnRH analogues and particularly estrogens (as in transgender hormone therapy), can have a considerable detrimental effect on fertility. This is largely a consequence of their antigonadotropic activity. Antigonadotropic agents like high-dose CPA, high-dose androgens (e.g., testosterone esters), and GnRH antagonists (though notably not GnRH agonists in the case of fertility) produce hypogonadism and high rates of severe or complete infertility (e.g., severe oligospermia or complete azoospermia) in men. However, these effects are fully and often rapidly reversible with their discontinuation, even after prolonged treatment. In contrast, while estrogens at sufficiently high dosages similarly are able to produce hypogonadism and to abolish or severely impair spermatogenesis, this is not necessarily reversible in the case of estrogens and can be long-lasting after prolonged exposure.
Pilot offers treatment for erectile dysfunction, premature ejaculation, hair loss, and weight management. Juniper provides GLP-1 receptor agonist therapy (such as Ozempic, Mounjaro and Wegovy) combined with health coaching for weight management. Software delivers online dermatology consultations and prescription skincare formulations. Kin provides reproductive health services including contraception, fertility support, and pregnancy care. Compound, a men's preventative health program launched in 2024, was paused later that year before relaunching in the UK in 2025. The company reported revenue of A$120.9 million in FY 2024, with 60% generated from international markets.
Sources: en.wikipedia.org
Epitalon is a synthetic tetrapeptide built from four amino acids: alanine, glutamate, aspartate, and glycine. It is not extracted from a natural source but made in the laboratory by chemical synthesis. Its short length makes it relatively straightforward to produce at high purity.
No naturally occurring free form of the peptide has been described. The four-amino-acid sequence can appear as a fragment within larger proteins, but that is not the same as the intact compound being present as a circulating molecule. Materials used in research are synthetic.
Purity is usually checked by reverse-phase high-performance liquid chromatography, which separates the target peptide from related impurities. Mass spectrometry is commonly used alongside it to confirm molecular mass. Some suppliers also provide amino acid analysis for additional sequence confirmation.
Reversed-phase high-performance liquid chromatography is run alongside mass spectrometry. The chromatogram separates components and gives a purity figure, while the mass spectrum confirms that the measured molecular mass matches the expected sequence. Neither measurement on its own is treated as sufficient.