Melanotan II comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Belongs to the melanocortin agonist family |
| Key substitutions | Nle4 and D-Phe7 | Improve resistance to enzymatic degradation |
| Molecular formula | C50H69N15O9 | Approximately 1024 g/mol |
| Regulatory status | Not approved as a medicine | Distributed as a research chemical |
| Common synonyms | Melanotan II, MT-II, MT-2 | Spelling varies across sources |
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
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.
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== Biosynthesis == Biosynthesis pathway of fumitremorgin pathway involves several different enzymes. FtmA is a nonribosomal peptide synthase. Both FtmB and FtmH are prenyltransferase. Three different cytochrome P450 monooxygenases involved in the biosynthesis of fumitremorgin C are FtmC, FtmE, and FtmG. Furthermore, FtmD is proposed to function as the methyltransferase. The synthesis starts with the formation of brevianamide F. FtmA catalyzes the nonribosomal peptide synthesis (NRPS) of this diketopiperazine product from two amino acids, L-tryptophan and L-proline. Then, another enzyme, FtmB, prenylates the product to form tryprostatin B. At this point, there are two separate pathways. FtmE may cyclize tryprostatin B to form demethoxyfumitremorgin C, or FtmC may oxidize tryprostatin B to form desmethyltrprostatin A by adding a hydroxyl group to the C-6 of the indole ring. The later pathway is followed by methylation to form tryprostatin A. The enzyme that catalyzes this methylation reaction has not been fully identified, but FtmD is suspected to be the plausible candidate. Then, the cyclization of tryprostatin A produces fumitremorgin C by forming the C-N bond by FtmE. The subsequent hydroxylation of fumitremorgin C takes place at C-12 and C-13 to form 12α, 13α-dihydroxyfumitremorgin C by FtmG. Fumitremorgin B is formed by another prenyltransferase, FtmH, that prenylates at N-1 of the indole ring (N-vinyl rather than N-prenyl incorrectly shown in the scheme below).
There is also significant doubt about whether β-arrestin is truly responsible for the side effects of opioids, and positive results suggesting G-protein activation may still produce constipation, respiratory depression, and tolerance. In summary, mitragynine pseudoindoxyl may still have a better therapeutic window compared to other full agonists, including other putatively biased G-protein agonists, but more research is needed to quantify this effect, particularly in humans, and to elucidate the cause. Cryo-EM structures of the μOR-Gi1 complex with mitragynine pseudoindoxyl and lofentanil (one of the most potent opioids) revealed that the two ligands engage distinct subpockets, and molecular dynamics simulations showed additional differences in the binding site that promote distinct active-state conformations on the intracellular side of the receptor where G proteins and β-arrestins bind. Importantly, studies have shown that oxidative metabolism is capable of transforming mitragynine (the main alkaloid in kratom) into mitragynine pseudoindoxyl in two steps, which is likely to influence kratom's complex pharmacological effects.
Sources: en.wikipedia.org
=== Toxicity === Iron is also potentially toxic. Its ability to donate and accept electrons means that it can catalyze the conversion of hydrogen peroxide into free radicals. Free radicals can cause damage to a wide variety of cellular structures, and ultimately kill the cell. Iron bound to proteins or cofactors such as heme is safe. Also, there are virtually no truly free iron ions in the cell, since they readily form complexes with organic molecules. However, some of the intracellular iron is bound to low-affinity complexes, and is termed labile iron or "free" iron. Iron in such complexes can cause damage as described above. To prevent that kind of damage, all life forms that use iron bind the iron atoms to proteins. This binding allows cells to benefit from iron while also limiting its ability to do harm. Typical intracellular labile iron concentrations in bacteria are 10–20 micromolar, though they can be 10-fold higher in anaerobic environment, where free radicals and reactive oxygen species are scarcer. In mammalian cells, intracellular labile iron concentrations are typically smaller than 1 micromolar, less than 5 percent of total cellular iron.
Though delayed a year to reach its first flight, Gemini was able to take advantage of the USSR's two-year hiatus after Voskhod, which enabled the US to catch up and surpass the previous Soviet superiority in piloted spaceflight. Gemini had ten crewed missions between March 1965 and November 1966: Gemini 3, Gemini 4, Gemini 5, Gemini 6A, Gemini 7, Gemini 8, Gemini 9A, Gemini 10, Gemini 11, and Gemini 12; and accomplished the following:
Researchers have not found enough variability within the genus to confidently delineate similar species, due to a low rate in mutation of mitochondrial DNA. Environmental factors, such as the rise of temperatures and acid levels in our oceans account for some speciation of corals in the form of species lost. Various coral species have heat shock proteins (HSP) that are also in the category of DE across species. These HSPs help corals combat the increased temperatures they are facing which lead to protein denaturing, growth loss, and eventually coral death. Approximately 33% of coral species are on the International Union for Conservation of Nature's endangered species list and at risk of species loss. Ocean acidification (falling pH levels in the oceans) is threatening the continued species growth and differentiation of corals. Mutation rates of Vibrio shilonii, the reef pathogen responsible for coral bleaching, heavily outweigh the typical reproduction rates of coral colonies when pH levels fall. Thus, corals are unable to mutate their HSPs and other climate change preventative genes to combat the increase in temperature and decrease in pH at a competitive rate to these pathogens responsible for coral bleaching, resulting in species loss.
Sources: en.wikipedia.org
=== Stability === "LSD," writes the chemist Alexander Shulgin, "is an unusually fragile molecule ... As a salt, in water, cold, and free from air and light exposure, it is stable indefinitely." LSD has two labile protons at the tertiary stereogenic C5 and C8 positions, rendering these centers prone to epimerisation. The C8 proton is more labile due to the electron-withdrawing carboxamide attachment, but the removal of the chiral proton at the C5 position (which was once also an alpha proton of the parent molecule tryptophan) is assisted by the inductively withdrawing nitrogen and pi electron delocalisation with the indole ring. LSD also has enamine-type reactivity because of the electron-donating effects of the indole ring. Because of this, chlorine destroys LSD molecules on contact; even though chlorinated tap water contains only a slight amount of chlorine, the small quantity of compound typical to an LSD solution will likely be eliminated when dissolved in tap water. The double bond between the 8-position and the aromatic ring, being conjugated with the indole ring, is susceptible to nucleophilic attacks by water or alcohol, especially in the presence of UV or other kinds of light. LSD often converts to lumi-LSD (10-hydroxy-9,10-dihydro-LSD), which is inactive in human beings. A controlled study was undertaken to determine the stability of LSD in pooled urine samples.
== Safety == In vivo dermal sensitization studies according to OECD 429 confirmed CMDT is a strong skin sensitizer, showing a response at 0.03 wt% in the local lymph node assay (LLNA) placing it in Globally Harmonized System of Classification and Labelling of Chemicals (GHS) Dermal Sensitization Category 1A. These studies confirm that DMTMM is a less sensitizing alternative to CDMT, as suggested by anecdotal observations in the literature.
== Formulation == Aulus Cornelius Celsus details one version of the antidote in De Medicina (ca. AD 30). A recent translation is as follows: "But the most famous antidote is that of Mithridates, which that king is said to have taken daily and by it to have rendered his body safe against danger from poison". It contained:
Sources: en.wikipedia.org
It is a synthetic cyclic peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.
No regulatory agency has approved it for any indication. It is encountered as a research chemical sold outside pharmaceutical supply chains. Products marketed this way are not subject to the manufacturing and labeling requirements that apply to approved drugs.
Reports describe increased skin pigmentation as well as side effects such as nausea, flushing, and changes to existing moles. Much of the evidence comes from small studies and case reports rather than large trials. The long-term safety profile is therefore uncertain.
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.