MC1R is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-04-16. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Melanocortin receptor agonist |
| Molecular formula | C50H69N15O9 | Neutral form, mass near 1024.2 g/mol |
| Primary targets | MC1R, MC3R, MC4R, MC5R | Binding is non-selective across subtypes |
| Related compounds | Alpha-MSH, melanotan I, afamelanotide | Structurally or functionally related peptides |
| Common abbreviations | MT-II, MT-2 | Naming in the literature is not uniform |
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.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
Lyophilized peptide powder is generally stored frozen, protected from light and moisture. Tryptophan residues are susceptible to oxidation, and the lactam bridge can hydrolyze under strongly acidic or basic conditions. Solutions prepared for laboratory work degrade faster than dry powder, and repeated freeze-thaw cycles accelerate loss. Common practice is to aliquot solutions before freezing and to avoid alkaline buffers. Reported stability windows vary with concentration, buffer, and temperature, so exact shelf lives are method-specific rather than universal.
Regulatory status differs by country, and in many places supplying the compound for human consumption is unlawful. Vendors frequently label material as intended for research use only, a designation that shifts stated purpose but does not create a legal pathway for personal use. Certificates of analysis accompanying such products vary widely in detail and provenance. Third-party testing exists but is voluntary, and results are rarely linked to a specific lot in a publicly verifiable way.
=== Inorganic nanoparticles === Drug delivery strategies of inorganic nanoparticles are dependent on material properties. The active targeting of inorganic nanoparticle drug carriers is often achieved by surface functionalization with specific ligands of nanoparticles. For example, the inorganic multifunctional nanovehicle (5-FU/Fe3O4/αZrP@CHI-FA-R6G) is able to accomplish tumor optical imaging and therapy simultaneously. It can be directed to the location of cancer cells with sustained release behavior. Studies have also been done on gold nanoparticle responses to local near-infrared (NIR) light as a stimuli for drug release. In one study, gold nanoparticles functionalized with double-stranded DNA encapsulated with drug molecules, were irradiated with NIR light. The particles generated heat and denatured the double-stranded DNA, which triggered the release of drugs at the target site. Studies also suggest that a porous structure is beneficial to attain a sustained or pulsatile release. Porous inorganic materials demonstrate high mechanical and chemical stability within a range of physiological conditions. The well-defined surface properties, such as high pore volume, narrow pore diameter distribution, and high surface area allow the entrapment of drugs, proteins and other biogenic molecules with predictable and reproducible release patterns.
== Formal scientific review == In 2006, the U.S. National Academy of Sciences released the report of a study of molecular manufacturing (not molecular assemblers per se) as part of a longer report, A Matter of Size: Triennial Review of the National Nanotechnology Initiative The study committee reviewed the technical content of Nanosystems, and in its conclusion states that no current theoretical analysis can be considered definitive regarding several questions of potential system performance, and that optimal paths for implementing high-performance systems cannot be predicted with confidence. It recommends funding for experimental research to produce experimental demonstrations in this area: "Although theoretical calculations can be made today, the eventually attainable range of chemical reaction cycles, error rates, speed of operation, and thermodynamic efficiencies of such bottom-up manufacturing systems cannot be reliably predicted at this time. Thus, the eventually attainable perfection and complexity of manufactured products, while they can be calculated in theory, cannot be predicted with confidence. Finally, the optimum research paths that might lead to systems which greatly exceed the thermodynamic efficiencies and other capabilities of biological systems cannot be reliably predicted at this time. Research funding that is based on the ability of investigators to produce experimental demonstrations that link to abstract models and guide long-term vision is most appropriate to achieve this goal."
Noribogaine is a hERG inhibitor and appears at least as potent as ibogaine. The inhibition of the hERG potassium channel delays the repolarization of cardiac action potentials, resulting in QT interval prolongation and, subsequently, in arrhythmias and sudden cardiac arrest. Ibogaine and the structurally related hallucinogen harmaline are tremorigenic, whereas noribogaine is not or is much less so. Noribogaine, but not ibogaine, produces potent psychoplastogenic effects in vitro in preclinical research. This can be blocked by the serotonin 5-HT2A receptor antagonist ketanserin, by the mTOR inhibitor rapamycin, and by a TrkB antagonist.
Sources: en.wikipedia.org
=== Drugs === The anti-diabetic medication pioglitazone was shown in a mouse model of ALD to be effective at treating the metabolic effects of ALD, including metabolic failure and increased oxidative stress. Pioglitazone was also shown to prevent axonal degeneration and increase mitochondria levels, as well as stop the progression of locomotor decline in ALD model mice. Subsequently, the experimental drug leriglitazone has been developed as a more brain penetrant metabolite of pioglitazone. As of 2023, leriglitazone is in phase 2/3 clinical trials for adult and childhood cALD in the USA and the EU, and has completed a clinical trial for AMN.
Journal of Molecular Biology. 206 (4): 759–777. doi:10.1016/0022-2836(89)90583-4. PMID 2500530. Milner-White, E (1990). "Situations of gamma-turns in proteinsTheir relation to alpha-helices, beta-sheets and ligand binding sites". J. Mol. Biol. 216 (2): 385–397. doi:10.1016/S0022-2836(05)80329-8. PMID 2254936. Hutchinson, E.G.; Thornton, J.M. (1994). "A revised set of potentials for β-turn formation in proteins". Protein Science. 3 (12): 2207–2216. doi:10.1002/pro.5560031206. PMC 2142776. PMID 7756980. Pavone V, Gaeta G, Lombardi A, Nastri F, Maglio O, Isernia C, Saviano M (1996). "Discovering protein secondary structures: classification and description of isolated alpha-turns". Biopolymers. 38 (6): 705–21. doi:10.1002/(SICI)1097-0282(199606)38:6<705::AID-BIP3>3.0.CO;2-V. PMID 8652792. Rajashankar KR, Ramakumar S (1996). "Pi-turns in proteins and peptides: Classification, conformation, occurrence, hydration and sequence". Protein Sci. 5 (5): 932–46. doi:10.1002/pro.5560050515. PMC 2143406. PMID 8732765.{{cite journal}}: CS1 maint: deprecated archival service (link) Shapovalov, M; Vucetic, S; Dunbrack RL, Jr (March 2019). "A new clustering and nomenclature for beta turns derived from high-resolution protein structures". PLOS Computational Biology. 15 (3) e1006844. Bibcode:2019PLSCB..15E6844S. doi:10.1371/journal.pcbi.1006844. PMC 6424458. PMID 30845191.
A gas chromatograph is made of a narrow tube, known as the column, through which the vaporized sample passes, carried along by a continuous flow of inert or nonreactive gas. Components of the sample pass through the column at different rates, depending on their chemical and physical properties and the resulting interactions with the column lining or filling, called the stationary phase. The column is typically enclosed within a temperature controlled oven. As the chemicals exit the end of the column, they are detected and identified electronically.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide and a non-selective melanocortin receptor agonist. Structurally it is modelled on alpha-melanocyte-stimulating hormone, a peptide that occurs naturally in the body.
Activation of MC1R increases pigment synthesis independently of ultraviolet exposure, which is the mechanism usually cited for darkening without sun exposure. Ultraviolet light still influences skin response through separate biological pathways.
Because the peptide binds several melanocortin receptor subtypes, its effects are not confined to pigmentation. This complicates interpretation of both intended and unintended outcomes reported in studies.
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.