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 2025-11-14 and is reviewed periodically as new material appears.
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.
Melanotan-2 has not received marketing authorisation from major regulatory agencies for any therapeutic indication. Several jurisdictions classify it as a prescription-only medicine or a controlled substance when supplied for human use. Because approved products do not exist, material sold online usually sits outside pharmaceutical supply chains and formal quality oversight. Regulators have issued public notices describing the compound as unapproved. Enforcement varies, and the legal position differs between countries, which complicates any single general statement about its status.
Scientific discussion of Melanotan-2 spans pharmacology, dermatology, and public-health literature. Laboratory studies examine its receptor binding and cellular effects, while clinical reports describe outcomes observed after unregulated use. These two bodies of work differ in rigour and intent. Peer-reviewed trials of the compound as a medicine are limited, so much of the available information comes from case reports and surveillance data. Authors frequently note the gap between experimental findings and real-world use.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analogue of alpha-melanocyte-stimulating hormone |
| Common synonyms | MT-II; melanotan 2 | No internationally accepted non-proprietary name |
| Typical presentation | Lyophilised powder in a sealed vial | Often supplied alongside a separate diluent |
| Regulatory status | Unapproved therapeutic substance | Customs seizure reported in several jurisdictions |
| Reported route in use | Subcutaneous injection | Self-administered outside clinical settings |
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
Quality assessment of research-grade peptide rests mainly on reversed-phase high-performance liquid chromatography for purity and on mass spectrometry for identity confirmation. A single main peak above a stated threshold, commonly ninety-eight percent by peak area, is the usual release criterion applied by suppliers. Independent analyses commissioned by laboratories and consumer organisations have repeatedly reported discrepancies between label claims and measured content, including truncated sequences, residual trifluoroacetate, and lower-than-declared peptide mass. Those findings do not establish that every supplier is unreliable, but they indicate that purity figures printed on a vial are claims requiring verification rather than settled facts.
Regulatory treatment varies by jurisdiction and has changed over time. In several countries the peptide is handled as an unapproved prescription medicine, and import or sale for human use is restricted, while elsewhere it falls under poisons or controlled-substance schedules. Enforcement activity against online vendors has been reported in Australia, New Zealand, the United Kingdom and the United States. Scholarly writing discusses melanotan-2 chiefly as an experimental tool and as a case study in unregulated peptide supply, and its precise legal position in any given country should be checked against current national schedules.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
=== Sources of toxicity === Diet – Liver is high in vitamin A. The liver of certain animals, including the polar bear, bearded seal, fish and walrus, are particularly toxic (see Liver (food) § Poisoning). It has been estimated that consumption of 500 grams (18 oz) of polar bear liver would result in an acute toxic dose for humans. Supplements – Dietary supplements can be toxic when taken above recommended dosages. Cod liver oil - According to the United States Department of Agriculture, a tablespoon (13.6 grams or 14.8 mL) of cod liver oil contains 4,080 μg of vitamin A. The tolerable upper intake level (UL) is 3000 μg/day for adults, 600 μg/day for children ages 1–3 years and 900 μg/day for children ages 4–8 years, so for all ages, but especially for young children, a tablespoon a day exceeds the UL.
It was taken to and put on display in Melbourne Zoo, but died on 12 September 1950. Taipan antivenom became available by mid-1955, and it was used for the first time on 10-year-old Bruce Stringer, who had been bitten at his school south of Cairns. As well as describing the Papuan taipan, Slater was instrumental in capturing and milking taipans both in New Guinea and Australia. In Bereina west of Port Moresby in 1957, Slater encountered a pair of taipans mating and bagged them, but was bitten by the male in the process. He managed to insert a syringe into a vein in his left ankle and give himself taipan antivenom. Despite this, he sickened and spent 10 days in hospital. Slater was the only person milking snakes for the PNG Department of Agriculture. After he resigned in 1959, the department announced they would pay £8/foot for each Papuan taipan caught; which equates to approximately $300 AUD/foot as of 2024. Dismayed, Slater feared that unskilled people would be emboldened to try to catch them; one person was reported to have died this way during this period. Coastal taipans were responsible for 4% (31 cases) of identified snakebite victims in Australia between 2005 and 2015, though no deaths were recorded in this cohort. At least one death from this species was recorded in a coronial retrospective study of snakebites from 2000 to 2016, and two between 1981 and 1991. Bites from the coastal taipan account for most snakebites in New Guinea in the rainy season, when the snake becomes more active, particularly in southern parts of the island.
== Preparation, occurrence, and applications == Phenyl groups are usually introduced using reagents that behave as sources of the phenyl anion or the phenyl cation. Representative reagents include phenyllithium (C6H5Li) and phenylmagnesium bromide (C6H5MgBr). Electrophiles are attacked by benzene to give phenyl derivatives:
Sources: en.wikipedia.org
Another fissile isotope, uranium-233, can be produced from natural thorium and is studied for future industrial use in nuclear technology. Uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons; uranium-235, and to a lesser degree uranium-233, have a much higher fission cross-section for slow neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors and produces the fissile material for nuclear weapons. The primary civilian use for uranium harnesses the heat energy to produce electricity. Depleted uranium (238U) is used in kinetic energy penetrators and armor plating. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the recently discovered planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal, and its radioactive properties were discovered in 1896 by Henri Becquerel. Research by Otto Hahn, Lise Meitner, Enrico Fermi and others (including J. Robert Oppenheimer), beginning in 1934, led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239. Dismantling of these weapons and related nuclear facilities is carried out within various nuclear disarmament programs and costs billions of dollars.
=== Parallel approach === Parallel engineering is also known as bioengineering. The basic genetic code is the foundation for parallel engineering research, which uses conventional biomolecules like nucleic acids and the 20 amino acids to construct biological systems. For a variety of applications in biocomputing, bioenergy, biofuels, bioremediation, optogenetics, and medicine, it involves the standardisation of DNA components, engineering of switches, biosensors, genetic circuits, logic gates, and cellular communication operators. For directing the expression of two or more genes and/or proteins, the majority of these applications often rely on the use of one or more vectors (or plasmids). Small, circular, double-strand DNA units known as plasmids, which are primarily found in prokaryotic but can also occasionally be detected in eukaryotic cells, may replicate autonomously of chromosomal DNA.
=== Differences between PAM and BLOSUM === PAM matrices are based on an explicit evolutionary model (i.e. replacements are counted on the branches of a phylogenetic tree: maximum parismony), whereas the BLOSUM matrices are based on an implicit model of evolution. The PAM matrices are based on mutations observed throughout a global alignment, this includes both highly conserved and highly mutable regions. The BLOSUM matrices are based only on highly conserved regions in series of alignments forbidden to contain gaps. The method used to count the replacements is different: unlike the PAM matrix, the BLOSUM procedure uses groups of sequences within which not all mutations are counted the same. Higher numbers in the PAM matrix naming scheme denote larger evolutionary distance, while larger numbers in the BLOSUM matrix naming scheme denote higher sequence similarity and therefore smaller evolutionary distance. Example: PAM150 is used for more distant sequences than PAM100; BLOSUM62 is used for closer sequences than BLOSUM50.
Sources: en.wikipedia.org
=== Topical === Side effects may include irritation of the skin and discoloration of clothing. A harsh burn on a child from an undissolved tablet has been reported. For treating eczema, it is recommended using for a few days at a time due to the possibility of it irritating the skin. Higher concentration solutions can result in chemical burns. Therefore, the British National Formulary recommends 100 mg be dissolved in a liter of water before use to form a 1:10,000 (0.01%) solution. Wrapping the dressings soaked with potassium permanganate is not recommended.
== Safety and regulation == Active packaging is designed to interact with the packaged product or the surrounding environment. The active function does not remove the requirement for the underlying packaging to comply with applicable food-contact, pharmaceutical, transport, environmental, and product-safety rules. In the European Union, Commission Regulation (EC) No 450/2009 establishes specific requirements for active and intelligent materials intended to come into contact with food. It defines active materials as materials designed to deliberately release or absorb substances in order to extend shelf life or maintain or improve food condition. Substances intended to migrate into food may also be subject to food-additive and labelling requirements. Components positioned behind a functional barrier must remain within applicable migration limits. Intelligent packaging must not provide misleading information about the condition or safety of a product. An indicator that makes spoiled food appear acceptable could create a safety risk. Safety assessment may include:
== In popular culture == In the 1998 film The Big Lebowski, after one of the protagonists dies, their ashes are transported to the Pacific Ocean in a Folgers coffee can because the cheapest urn is deemed too expensive. The film has become a cult classic, and at least one person has dressed up as a can of Folgers during a fan event. In the 1991 Seinfeld episode "The Library", Jerry is challenged by Lt. Bookman (played by Philip Baker Hall) on why there is no instant coffee available for guests to his apartment: "You buy a jar of Folger's Crystals, you put it in the cupboard, you forget about it. Then later on when you need it, it's there. It lasts forever. It's freeze-dried. Freeze-dried crystals." The November 16, 1991 episode of Saturday Night Live had a sketch that parodied the 'high end restaurant' commercials from the 1970s and 1980s, showing a customer (Chris Farley) violently losing his temper upon being informed that he was given another company's coffee blend instead of the restaurant's usual blend.
== Treatment == Management of acanthosis nigricans (AN) generally involves evaluating for and addressing any associated underlying condition rather than treating the skin changes alone. When AN occurs in the setting of obesity, insulin resistance or type 2 diabetes mellitus, improvement in metabolic status may be followed by gradual softening or lightening of the lesions, although the degree of change varies. Drug-induced AN may improve after reduction or discontinuation of the causative medication when clinically appropriate. Reported associations include systemic corticosteroids, high-dose nicotinic acid and certain hormonal therapies. In malignancy-associated AN, particularly that linked to gastrointestinal adenocarcinomas, regression of the cutaneous changes has been observed following treatment of the underlying tumour, though this is not universal. Sudden onset, rapid progression or mucosal involvement have been described in malignant forms and may prompt further evaluation.
Sources: en.wikipedia.org
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.
It was developed in the 1980s by researchers investigating analogues of alpha-melanocyte-stimulating hormone for pigmentation and related endpoints. Early work included small human studies during the 1990s. Development did not progress to licensing, and the compound remained a research and grey-market item.
Peptides are prone to truncation, oxidation and aggregation during synthesis and handling. Without independent testing, a buyer cannot confirm the identity or the content of a vial. Analytical surveys of unapproved peptide products have repeatedly found discrepancies between label claims and measured composition.
Major regulatory agencies have not approved it for any indication. Some countries permit it only under prescription frameworks, while others classify it as a controlled substance.