A practical reference on melanocortin receptors: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
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.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
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.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
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.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
==== Synthesis of crown ethers ==== A series of polynomial heterocyclic compounds, known as crown ethers, can be synthesized with ethylene oxide. One method is the cationic cyclopolymerization of ethylene oxide, limiting the size of the formed cycle:
He is also related to Leonard Wolfson, Baron Wolfson, Miel de Botton and Janet Wolfson de Botton, Trustee of Tate and Chairman of the Council of Tate Modern and appointed Commander of the Most Excellent Order of the British Empire (CBE) in 2006 and elevated to Dame Commander of the Order of the British Empire (DBE) in the 2013 Birthday Honours for charitable services to the arts. Caryl Brahms writer Julius Braunthal (1891–1972) was an Austrian Jewish historian, magazine editor, and political activist; Secretary of the Socialist International from 1951 to 1956; wrote three volume History of the International, first published in German between 1961 and 1971. David Bret biographer, broadcaster and chansonnier (French-born; Jewish father) Jacob Bronowski (18 January 1908 – 22 August 1974) Polish-British mathematician, philosopher, academic and author of more than eighteen scholarly books, focusing on William Blake, magic and evolution; is best known for developing a humanistic approach to science, and as the presenter and writer of the 1973 BBC television documentary series, and accompanying book The Ascent of Man, which led to his regard as "one of the world's most celebrated intellectuals". Anita Brookner (16 July 1928 – 10 March 2016) of Polish Jewish ancestry, novelist and art historian; Slade Professor of Fine Art at the University of Cambridge from 1967 to 1968; first woman to hold this visiting professorship; awarded Booker–McConnell Prize for her novel Hotel du Lac. Sam Bourne novelist pseudonym of Jonathan Freedland.
Several mutations in Rho proteins have been identified in large scale sequencing of cancers. These mutations are listed in the Catalogue of Somatic Mutations database (http://www.sanger.ac.uk/genetics/CGP/cosmic/). The functional consequences of these mutations are unknown.
=== Humans and other mammals === Humans and other mammals have chitinase and chitinase-like proteins that can degrade chitin; they also possess several immune receptors that can recognize chitin and its degradation products, initiating an immune response. Chitin is sensed mostly in the lungs or gastrointestinal tract where it can activate the innate immune system through eosinophils or macrophages, as well as an adaptive immune response through T helper cells. Keratinocytes in skin can also react to chitin or chitin fragments.
DCI John Caldwell, an off duty Police Service of Northern Ireland officer, is injured in Omagh after being shot by suspected New IRA gunman. 23 February Labour leader Sir Keir Starmer outlines the five key issues that his party will focus on during the run up to the 2024 general election: higher economic growth, clean energy, improving the NHS, reforming the justice system, and raising education standards. Environment Secretary Thérèse Coffey, commenting on the vegetable shortage, tells MPs "we anticipate the situation will last about another two to four weeks". Three men are arrested in relation to the previous evening's shooting of DCI John Caldwell. 24 February The British Medical Association announces that junior doctors in England will begin a three-day strike on 13 March. An earthquake measuring 3.7 magnitude strikes Brynmawr, Blaenau Gwent at 11.59pm. COVID-19 in the UK: Office for National Statistics data for the week up to 14 February indicates COVID-19 cases continued to rise in England, Scotland and Wales, but remained uncertain in Northern Ireland. In England, the estimated number of people testing positive for COVID-19 was 1,223,000 (or 2.18% of the population and around 1 in 45 people). 27 February New Transgender Policy Guidance for England and Wales came into force on 27 February 2023 under which transgender women offenders would no longer be housed in women's prisons if they had male genitalia or had committed sex crimes.
Sources: en.wikipedia.org
The first treatments with Adelaide-produced insulin were delivered by Robertson's Medical Science Club colleague, Dr. Trent Champion de Crespigny (Honorary Physician to the Adelaide Children's Hospital). The first treated was gravely-ill 9 years-old Dawson Hanna (1913–1926), at the Adelaide Children's Hospital on 7 January 1923, who lived for another three years. The first adult treated with Adelaide-produced insulin was the comatose and moribund 34 years-old Clifford Harry Cornish (1888–1954), at the Adelaide Hospital on 31 January 1923, who lived for another thirty years. All of the Adelaide-produced insulin used for these treatments had been delivered "free of charge" to the patients.
In May 2026, the federal election watchdog announced Findlay was under investigation over expenses for her failed re-election bid. Elections Canada alleges Findlay received $75,000 in undeclared and unpaid services from a corporation in exchange for promised federal contracts. They further suggest that approximately 50 individuals described as foreign nationals without legal status, canvassed on behalf of Findlay. In response, Findlay threatened legal action against the media for publishing any story mentioning these allegations.
=== Low glutathione levels === Kwashiorkor is also marked by low glutathione levels. Glutathione is used in many of the body processes on a molecular level. It is believed to be related to high oxidant levels commonly seen in people who suffer from starvation and rarely in chronic inflammation. Glutathione serves vital functions including management of oxidative stress which is an imbalance that plays a key role in the pathogenesis of many diseases. Evidence indicates that amino acid balance has an important effect on protein nutrition and therefore on glutathione homeostasis. Cysteine is an essential amino acid that acts as the limiting amino acid for glutathione synthesis in humans. Factors that increase demand for glutathione may increase demand for cysteine, and hence methionine. Such demands have been hypothesized to increase the risk for kwashiorkor.
=== Gene expression modulation and epigenetics === Apart from classical pharmacological targets, drugs may exert effects through direct or indirect gene expression modulation, or even introduce persistent state changes through epigenetic reprogramming. Therefore, drugs should be screened for off-target activity by gene expression profiling, in addition to conventional ligand binding, enzyme assays, etc.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
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.