This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-07-20 and is reviewed periodically as new material appears.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Their enhanced catalytic activity over other ligands in palladium-catalyzed coupling reactions have been attributed to their electron-richness, steric bulk, and some special structural features. In particular, cyclohexyl, t-butyl, and adamantyl groups on the phosphorus are used for this purpose as bulky, electron-donating substituents. The lower ring of the biphenyl system, ortho to the phosphino group, is also a key structural feature. Numerous crystallographic studies have indicated that it behaves as a hemilabile ligand and is believed to play a role in stabilizing the highly reactive, formally 12-electron L–Pd0 intermediate during the catalytic cycle. 2,6-Substitution on the lower ring minimizes catalyst decomposition via Pd-mediated C-H activation of these positions. Extensive experimentation by the Buchwald group has shown that further minor changes to the structure of these ligands can dramatically alter their catalytic activity in cross coupling reactions with different substrates. This has led to the evolution of multiple ligands that are tailored for specific transformations. By providing a means of generating the postulated catalytically active L–Pd0 species under mild conditions (room temperature or lower in many cases), the development of several generations of base-activated, cyclopalladated precatalysts have further broadened the applicability of the ligands and simplified their use.
Triple-stranded DNA (also known as H-DNA or Triplex-DNA) is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In triple-stranded DNA, the third strand binds to a B-form DNA (via Watson–Crick base-pairing) double helix by forming Hoogsteen base pairs or reversed Hoogsteen hydrogen bonds.
Most rheumatic diseases are treated with analgesics, NSAIDs (nonsteroidal anti-inflammatory drug), steroids (in serious cases), DMARDs (disease-modifying antirheumatic drugs), monoclonal antibodies, such as infliximab and adalimumab, the TNF inhibitor etanercept, and methotrexate for moderate to severe rheumatoid arthritis. The biologic agent rituximab (anti-B cell therapy) is now licensed for use in refractory rheumatoid arthritis. Physiotherapy is vital in the treatment of many rheumatological disorders. Occupational therapy can help patients find alternative ways for common movements that would otherwise be restricted by their disease. Patients with rheumatoid arthritis often need a long term, coordinated and a multidisciplinary team approach towards management of individual patients. Treatment is often tailored according to the individual needs of each patient which is also dependent on the response and the tolerability of medications. Beginning in the 2000s, the incorporation of biopharmaceuticals (which include inhibitors of TNF-alpha, certain interleukins, and the JAK-STAT signaling pathway) into standards of care is one of the paramount developments in modern rheumatology.
Blood is drawn into a test tube containing liquid sodium citrate, which acts as an anticoagulant by binding the calcium in a sample. The blood is mixed, then centrifuged to separate blood cells from plasma (as prothrombin time is most commonly measured using blood plasma). In newborns, a capillary whole blood specimen is used. A sample of the plasma is extracted from the test tube and placed into a measuring test tube (Note: for an accurate measurement, the ratio of blood to citrate needs to be fixed and should be labeled on the side of the measuring test tube by the manufacturing company; many laboratories will not perform the assay if the tube is underfilled and contains a relatively high concentration of citrate—the standardized dilution of 1 part anticoagulant to 9 parts whole blood is no longer valid). Next an excess of calcium (in a phospholipid suspension) is added to the test tube, thereby reversing the effects of citrate and enabling the blood to clot again. Finally, in order to activate the extrinsic / tissue factor clotting cascade pathway, tissue factor (also known as factor III) is added and the time the sample takes to clot is measured optically. Some laboratories use a mechanical measurement, which eliminates interferences from lipemic and icteric samples.
Sources: en.wikipedia.org
===== Endangered species and other wild animals ===== Some compounds can include the parts of endangered species, including tiger bones and rhinoceros horn which is used for many ailments (though not as an aphrodisiac as is commonly misunderstood in the West). The black market in rhinoceros horns (driven not just by TCM but also unrelated status-seeking) has reduced the world's rhino population by more than 90 percent over the past 40 years. Concerns have also arisen over the use of pangolin scales, turtle plastron, seahorses, and the gill plates of mobula and manta rays. Poachers hunt restricted or endangered species to supply the black market with TCM products. There is no scientific evidence of efficacy for tiger medicines. Concern over China considering to legalize the trade in tiger parts prompted the 171-nation Convention on International Trade in Endangered Species (CITES) to endorse a decision opposing the resurgence of trade in tigers. Fewer than 30,000 saiga antelopes remain, the horns of which are illegally exported to China by organized gangs to be used in traditional fever therapies. The pressures on seahorses (Hippocampus spp.) used in traditional medicine is enormous; tens of millions of animals are unsustainably caught annually. Many species of syngnathid are currently part of the IUCN Red List of Threatened Species or national equivalents. The deer penis is believed to have therapeutic benefits according to traditional Chinese medicine. Tiger parts from poached animals include tiger penis, believed to improve virility, and tiger eyes.
In the late 6th century, following Justinian I's wars, seven mobile field armies called comitatenses, numbering around 150,000 troops, were deployed around the empire; they remained the finest armies in Europe. They were aided by twenty-five frontier garrisons of approximately 195,000 lower-quality limitanei troops. Additional troops included subsidised allied forces and imperial guard units like the Scholae Palatinae. Naval forces were limited: flotillas were based at key locations, while 30,000 oarsmen were assembled to row 500, mostly requisitioned, transports to support the Vandalic War in Africa in 533. The losses suffered in the 7th-century Arab conquests led to fundamental changes. The field armies were withdrawn into the core Anatolian territories and assigned to settle in specific districts, which became known as themata and eventually replaced the old provinces. The thematic armies, supported by the proceeds of their districts, came to resemble a provincial militia with a small professional core, aided by foreign mercenaries and imperial regiments at Constantinople. To defend against its new Muslim enemy, the navy was similarly reorganised into several provincialised fleets. It became the dominant power in the eastern Mediterranean, with dromons equipped with Greek fire proving crucial on several occasions. As the 8th-century empire stabilised, the thematic militias proved rebellious and only suitable for defensive operations.
=== Applications === The most widespread application of copper-free click chemistry is in biological imaging in live cells or animals using an azide-tagged biomolecule and a cyclooctyne bearing an imaging agent. Fluorescent keto and oxime variants of DIBO are used in fluoro-switch click reactions in which the fluorescence of the cyclooctyne is quenched by the triazole that forms in the reaction. On the other hand, coumarin-conjugated cyclooctynes such as coumBARAC have been developed such that the alkyne suppresses fluorescence while triazole formation increases the fluorescence quantum yield by ten-fold.
In the body, stores of fat are referred to as adipose tissue. In these areas, intracellular triglycerides are stored in cytoplasmic lipid droplets. When lipase enzymes are phosphorylated, they can access lipid droplets and through multiple steps of hydrolysis, breakdown triglycerides into fatty acids and glycerol. Each step of hydrolysis leads to the removal of one fatty acid. The first step and the rate-limiting step of lipolysis is carried out by adipose triglyceride lipase (ATGL). This enzyme catalyzes the hydrolysis of triacylglycerol to diacylglycerol. Subsequently, hormone-sensitive lipase (HSL) catalyzes the hydrolysis of diacylglycerol to monoacylglycerol and monoacylglycerol lipase (MGL) catalyzes the hydrolysis of monoacylglycerol to glycerol. Perilipins are proteins that act as a physical shield or dynamic scaffold, preventing lipolytic enzymes in the cytosol from accessing the stored triglycerides during periods of energy abundance. Perilipin 1A is a key protein regulator of lipolysis in adipose tissue. This lipid droplet-associated protein, when deactivated, will prevent the interaction of lipases with triglycerides in the lipid droplet and grasp the ATGL co-activator, comparative gene identification 58 (CGI-58) (a.k.a. ABHD5). When perilipin 1A is phosphorylated by PKA, it releases CGI-58 and it expedites the docking of phosphorylated lipases to the lipid droplet. CGI-58 can be further phosphorylated by PKA to assist in its dispersal to the cytoplasm. In the cytoplasm, CGI-58 can co-activate ATGL.
According to Panorama investigation, Daniel has operated in the boxing industry through MTK and simultaneously operated Europe's biggest money laundering, drug trafficking, and gangland executions networks from Dubai. A spokesperson for minister O'Brien said, "respect for human rights is a cornerstone of Ireland's foreign policy," when asked if the minister would raise the concerns regarding Daniel's presence and operations in Dubai on his visit in March 2022 for St Patrick's Day. The European Union placed the UAE on its money laundering blacklist, in December 2022. It implied that the EU considers the Emirates a high-risk nation that presents "strategic deficiencies in the anti–money laundering countering the financing of terrorism regimes". The move was taken amid the conflict against the Kinahan Organised Crime Group (KOCG), and was expected to push the authorities to take proactive measures against members of the Kinahan cartel. In July 2025, the European Commission revised its list of high-risk jurisdictions for money laundering and terrorism financing, which excluded the UAE. The European Parliament voted in favor of the updated list, which was earlier opposed by the MEPs. The decision to remove the Emirates from the EU money laundering blacklist was criticized by Transparency International, which said the country’s reforms cannot be considered effective yet. The EU listing process also came into question for not allowing the Parliament to assess the countries individually.
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
No regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.