A practical reference on melanocortin receptor: 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.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
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.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Lyophilised cake or flake |
| Solubility class | Soluble in water and aqueous buffer | Also soluble in some polar organic solvents |
| Typical storage temperature | Minus 20 degrees Celsius or below | Desiccated and protected from light |
| Typical analytical method | LC-MS/MS | Reversed-phase separation with mass detection |
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
Analytical confirmation of identity relies on mass spectrometry, most often coupled to liquid chromatography. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and provides a purity estimate based on peak area. Electrospray ionization mass spectrometry then confirms the expected molecular mass, while tandem mass spectrometry can map the fragment sequence. For research-grade material, these two techniques together form the standard minimum. Purity figures reported by vendors are frequently not traceable to an independent laboratory.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference material.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
== History == Athletes in ancient Greece were advised to consume large quantities of meat and wine. A number of herbal concoctions and tonics have been used by strong men and athletes since ancient times across cultures to try to increase their strength and stamina. In the 1910s, Eugen Sandow, widely considered to be the first modern bodybuilder in the West, advocated the use of dietary control to enhance muscle growth. Later, bodybuilder Earle Liederman advocated the use of "beef juice" or "beef extract" (basically, consommé) as a way to enhance muscle recovery. In the 1950s, with recreational and competitive bodybuilding becoming increasingly popular, Irvin P. Johnson began to popularize and market egg-based protein powders marketed specifically at bodybuilders and physical athletes. The 1970s and 1980s marked a dramatic increase in the growth of the bodybuilding supplement industry, fueled by the widespread use of modern marketing techniques and a marked increase in recreational bodybuilding. In October 1994, the Dietary Supplement Health and Education Act (DSHEA) was signed into law in the USA. Under DSHEA, responsibility for determining the safety of the dietary supplements changed from the government to the manufacturer, and supplements no longer required approval from the U.S. Food and Drug Administration (FDA) before distributing the products. Since that time, manufacturers did not have to provide FDA with the evidence to substantiate safety or effectiveness unless a new dietary ingredient was added.
=== Plants === Potassium is crucial for diverse plant species. It has a vital role in maintaining cell sap and internal root pressure required for plant growth. Potassium increases plant metabolism and uptake of carbon dioxide.
Expression. The 5-HT3C, 5-HT3D and 5-HT3E genes tend to show peripherally restricted pattern of expression, with high levels in the gut. In human duodenum and stomach, for example, 5-HT3C and 5-HT3E mRNA might be greater than for 5-HT3A and 5-HT3B. Polymorphism. In patients treated with chemotherapeutic drugs, certain polymorphism of the HTR3B gene could predict successful antiemetic treatment. This could indicate that the 5-HTR3B receptor subunit could be used as biomarker of antiemetic drug efficacy.
==== Supercritical CO2 ==== Food scientists have also turned to supercritical carbon dioxide (sCO2) as a means of decaffeination. Developed by Kurt Zosel, a scientist of the Max Planck Institute, it uses CO2 (carbon dioxide), heated and pressurised above its critical point, to extract caffeine. Green coffee beans are steamed and then added to a high pressure vessel. A mixture of water and CO2 is circulated through the vessel at 300 atm and 65 °C (149 °F). At this pressure and temperature CO2 is a supercritical fluid, with properties midway between a gas and a liquid. Caffeine dissolves into the CO2; but compounds contributing to the flavour of the brewed coffee are largely insoluble in CO2 and remain in the bean. In a separate vessel, caffeine is scrubbed from the CO2 with additional water. The CO2 is then recirculated to the pressure vessel. The purity of the recovered caffeine in this process is above 90%, directly from the process. The biggest industrial plant, which is producing 10,000 tons of decaffeinated coffee per year is currently in operation at Luigi Lavazza S.p.A. in Italy.
Sources: en.wikipedia.org
=== Electric vehicles === In February 2023, Moore introduced the Clean Transportation and Energy Act, which increases incentives for people and businesses looking to purchase electric trucks and charging stations. In March 2023, he said he supported adopting California's Advanced Clean Cars II (ACC II) regulation, which would phase out the sale of gas-powered cars in the state by 2035. In April 2023, he signed the Clean Transportation and Energy Act and several other bills aimed at strengthening the state's offshore wind energy industry into law. In August 2023, Moore said he supported a proposal by then-Governor Hogan to delay emissions testing on new cars from three to six years—despite initially withdrawing the proposal earlier in his term due to equity concerns—after the Maryland Motor Vehicle Administration found that the change would have no severe impacts on equity. In April 2025, as Maryland electric vehicle sales continued to lag behind the state's goals, Moore signed an executive order to delay fines against car companies that fail to comply with the state's electric vehicle mandates.
UPMC Children's Hospital of Pittsburgh, (CHP), popularly known simply as "Children's", is part of the University of Pittsburgh Medical Center, and the only hospital in Southwestern Pennsylvania dedicated solely to the care of infants, children, teens and young adults well into their 20s and beyond, generally stopping around age 26. UPMC Children's also sometimes even treats older adults that require pediatric care. Care is provided by more than 700 board-certified pediatricians and pediatric specialists. Children's also provides primary care and specialty care at over 30 locations throughout the Pittsburgh region, as well as clinical specialty services throughout western Pennsylvania at regional health care facilities. UPMC Children's Hospital of Pittsburgh was one of only eight pediatric hospitals in the United States to make U.S. News & World Report's 2010-11 Best Children's Hospitals Honor Roll and is ranked in all ten of the specialties evaluated by US News. Children's is also one of only eight children's hospitals in the United States to be named as a Leapfrog Top Hospital and was ranked sixth in the nation by Parents magazine. UPMC Children's Hospital of Pittsburgh is a specialty hospital of UPMC, specializing in pediatrics and is located two and a half miles from UPMC Presbyterian in the Lawrenceville neighborhood of Pittsburgh. Serving as UPMC's primary pediatrics facility, it was originally located adjacent to UPMC Presbyterian in Oakland.
== Criticism == The use of protective groups is pervasive but not without criticism. In practical terms their use adds two steps (protection-deprotection sequence) to a synthesis, either or both of which can dramatically lower chemical yield. Crucially, added complexity impedes the use of synthetic total synthesis in drug discovery. In contrast biomimetic synthesis does not employ protective groups. As an alternative, Baran presented a novel protective-group free synthesis of the compound hapalindole U. The previously published synthesis according to Baran, contained 20 steps with multiple protective group manipulations (two confirmed):
Sources: en.wikipedia.org
The inner walls of the capsule are then rinsed with a dilute NaOH solution to collect iodine as soluble iodide (I−) and hypoiodite (IO−), according to the standard disproportionation reaction of halogens in alkaline solution. Any caesium atom present immediately oxidizes and passes into the water as Cs+. In order to eliminate any long-lived 135Cs and 137Cs which may be present in small amounts, the solution is passed through a cation-exchange column, which exchanges Cs+ for another non-radioactive cation (e.g., Na+). The radioiodine (as anion I− or IO−) remains in solution as a mixture of iodide and hypoiodite.
=== Predators === Newborn rattlesnakes are heavily preyed upon by a variety of species, including cats, ravens, crows, roadrunners, raccoons, opossums, skunks, coyotes, weasels, whipsnakes, kingsnakes, and racers. Young of the smaller crotaline species are frequently killed and eaten by small predatory birds, such as jays, kingfishers, and shrikes. Some species of ants in the genus Formica are known to prey upon neonates, and Solenopsis invicta (fire ants) likely do, as well. On occasion, hungry adult rattlesnakes cannibalize neonates. The small proportion (often as few as 20%) of rattlesnakes that make it to their second year are heavily preyed upon by a variety of larger predators, including coyotes, eagles, hawks, owls, falcons, feral pigs, badgers, indigo snakes, and kingsnakes. The common kingsnake (Lampropeltis getula), a constrictor, is immune to the venom of rattlesnakes and other vipers, and rattlesnakes form part of its natural diet. Rattlesnakes sense kingsnakes' presence by their odor. When they realize a kingsnake is nearby, they begin enacting a set of defensive postures known as "body bridging". Unlike its normal erect and coiled defensive-striking posture, the rattlesnake keeps its head low to the ground in an attempt to prevent the kingsnake from gaining a hold on it (the head being the first part of the rattlesnake to be ingested). The rattlesnake jerks its body about, while bridging its back upwards, forming an elevated coil that faces the kingsnake. The elevated coil is used to strike the attacker, and is also used to shield the head from the kingsnake.
DNA polymerase replication errors during cell division may lead to spontaneous missense mutations if DNA polymerase's proofreading ability does not detect and repair an error it makes. Spontaneous DNA polymerase errors are estimated to occur at a frequency of 1/109 base pairs. Although rarer, tautomerization of bases also creates spontaneous missense mutations. Tautomerization occurs when hydrogen atoms on DNA bases spontaneously change locations, impacting the structure of the base, and allowing it to pair with an incorrect base. If this strand of DNA is replicated, the incorrect base will be the template for a new strand, leading to a mutation, possibly changing the amino acid and therefore, the protein. For example, Wang et al., (2011) used X-ray cystallography to demonstrate that a de novo mutation was created when DNA repair mechanisms did not recognize a C-A base mismatch due to tautomerization allowing the base structures to be compatible.
The First Indochina War, known alternatively as the French Indochina War, was fought in French Indochina between the French Union and the Viet Minh and their respective allies, from 19 December 1946 until 11 August 1954. Most of the engagements of this conflict occurred in Vietnam. At the Potsdam Conference in July 1945, the Allied Combined Chiefs of Staff decided that Indochina south of latitude 16° north was to be included in the South East Asia Command under British Admiral Mountbatten. On 25 August 1945, Vietnamese Emperor Bảo Đại abdicated, handing power over to the Viet Minh. On 2 September, Ho Chi Minh proclaimed the establishment of the Democratic Republic of Vietnam (DRV). Also in September 1945, Chinese forces entered Hanoi, and Japanese forces north of the 16th parallel surrendered to Generalissimo Chiang Kai-shek. At the same time, British forces landed in Saigon, and Japanese forces in the south surrendered to the British. The Chinese Nationalists acknowledged the DRV and the communist-led Viet Minh, then in power in Hanoi. The British refused to do that in Saigon, in deference to the French. On 23 September 1945, French forces overthrew the Viet Minh administration in Saigon and declared French authority restored south of the 16th parallel. Guerrilla warfare began around Saigon immediately. After one year of low-level conflicts and failed negotiations, all-out war broke out in December 1946 between French and Viet Minh forces.
Sources: en.wikipedia.org
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.
No. Lyophilisation slows degradation rather than stopping it, and the rate depends on residual moisture, temperature and light exposure. Freezer storage extends useful life but does not make the material permanent.
A certificate is only as good as its traceability to a specific batch and a named laboratory. Documents lacking batch numbers, method descriptions or laboratory identifiers carry little weight. Confirming what was actually received generally requires a separate test of the material in hand.
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.