This is a working overview of alpha-MSH analogue, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-07-14 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Synthetic cyclic heptapeptide |
| Molecular mass | Approximately 1024 g/mol | Depends on counter-ion content |
| Appearance | White to off-white powder | Commonly supplied as a lyophilised solid |
| Solubility | Freely soluble in water | Also dissolves in common aqueous buffers |
| Typical storage | -20 degrees Celsius, desiccated | Protect from light and repeated freeze-thaw |
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.
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 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.
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.
=== Interactions === The H2-receptor antagonist cimetidine causes an increase in the plasma concentration of metformin by reducing clearance of metformin by the kidneys; both metformin and cimetidine are cleared from the body by tubular secretion, and both, particularly the cationic (positively charged) form of cimetidine, may compete for the same transport mechanism. A small double-blind, randomized study found the antibiotic cephalexin to also increase metformin concentrations by a similar mechanism; theoretically, other cationic medications may produce the same effect. Metformin also interacts with anticholinergic medications, due to their effect on gastric motility. Anticholinergic drugs reduce gastric motility, prolonging the time drugs spend in the gastrointestinal tract. This impairment may lead to more metformin being absorbed than without the presence of an anticholinergic drug, thereby increasing the concentration of metformin in the plasma and increasing the risk for adverse effects.
=== Performance === Nicotine-containing products are sometimes used for the performance-enhancing effects of nicotine on cognition. A 2010 meta-analysis of 41 double-blind, placebo-controlled studies concluded that nicotine or smoking had significant positive effects on aspects of fine motor abilities, alerting and orienting attention, and episodic and working memory. A 2015 review noted that stimulation of the α4β2 nicotinic receptor is responsible for certain improvements in attentional performance; among the nicotinic receptor subtypes, nicotine has the highest binding affinity at the α4β2 receptor (Ki=1 nM), which is also the biological target that mediates nicotine's addictive properties. Nicotine has potential beneficial effects, but it also has paradoxical effects, which may be due to the inverted U-shape of the dose-response curve or pharmacokinetic features.
== Further reading == Laurence, J (2015). "Centennial celebration of Translational Research: The Journal of Laboratory and Clinical Medicine". Translational Research. 165 (1): 1–6. doi:10.1016/j.trsl.2014.08.004. PMID 25301250. Hammerschmidt, DE (2004). "A new look and a heightened focus: Translational medicine and the Journal of Laboratory and Clinical Medicine". Journal of Laboratory and Clinical Medicine. 144 (1): 5–6. doi:10.1016/j.lab.2004.05.006. Vaughan, WT (1940). "We celebrate our silver anniversary". Journal of Laboratory and Clinical Medicine. 26 (1): 1–3.
In 1952, Stanley Miller and Harold Urey carried out a chemical experiment to demonstrate how organic molecules could have formed spontaneously from inorganic precursors under prebiotic conditions like those posited by the Oparin–Haldane hypothesis. It passed an electric current through a highly reducing (lacking oxygen) mixture of gases—methane, ammonia, and hydrogen, with water vapor—to form organic monomers such as amino acids. Bernal said of the Miller–Urey experiment that "it is not enough to explain the formation of such molecules, what is necessary, is a physical-chemical explanation of the origins of these molecules that suggests the presence of suitable sources and sinks for free energy." However, current scientific consensus describes the primitive atmosphere as weakly reducing or neutral, diminishing the amount and variety of amino acids that could be produced. The addition of iron and carbonate minerals, present in early oceans, produces a diverse array of amino acids. Later work has focused on two other potential reducing environments: outer space and deep-sea hydrothermal vents.
==== Geriatric use ==== For patients 65 years and older, it is unclear if there is a difference in response. However, older people often have decreased liver and kidney function which may lead to an increased level of naloxone in their body.
Sources: en.wikipedia.org
He will remain as an independent councillor for Tamworth. Martin Murray is appointed as temporary leader of Staffordshire County Council to replace him. 10 December – Chancellor Rachel Reeves tells the House of Commons that there were too many pre-budget leaks prior to her speech in November. Former swimmer Sharron Davies is named as one of three new Conservative peers; 25 new Labour peers and five Liberal Democrat peers are also announced. 11 December – Ben Bradley, a former Conservative MP and council leader, announces he is joining Reform UK. 12 December – The Treasury Committee launches a review of the Office for Budget Responsibility after it came under close scrutiny in the run up to the budget. Reform UK claims to have the largest party membership in the UK after a report in The Times that Labour's membership has fallen to below 250,000. Reform says it has 268,000 members, although political parties' figures are not externally verified. Reform wins its first election in Scotland after David McLennan is elected as a councillor in Whitburn and Blackburn in West Lothian, taking the seat from Scottish Labour. 14 December – Writing in The Sunday Telegraph, Conservative Party leader Kemi Badenoch says her party will scrap the impending UK ban on petrol and diesel vehicles if they win the next general election. 15 December – Former Democratic Unionist Party councillor William Ball is sentenced to fifteen months in custody for historical sexual offences committed against a young girl.
=== "Disc-at-risk" === The term "disc-at-risk" refers to an optic nerve head characterized by a small cup-to-disc ratio and a crowding of optic nerve fibers. This anatomical feature is a significant factor in the development of NAION. Individuals predisposed to this condition typically have smaller optic discs with minimal or no cupping. This anatomical configuration leads to a congestion of nerve fibers, which can contribute to the onset of NAION. This mechanism is somewhat similar to compartment syndrome, where increased pressure within a confined space impairs blood flow and tissue function.
== Regulation of prolactin secretion == Because lactotrophs are constitutively active, prolactin secretion operates through a "release from inhibition" model. Several inhibitory and stimulatory factors modulate the system.
=== Weight loss === Excess body weight is thought to be an important cause of sleep apnea. People who are overweight have more tissues in the back of their throat which can restrict the airway, especially when sleeping. In weight loss studies of overweight individuals, those who lose weight show reduced apnea frequencies and improved apnoea–hypopnoea index (AHI). Weight loss effective enough to relieve obesity hypoventilation syndrome (OHS) must be 25–30% of body weight. For some obese people, it can be difficult to achieve and maintain this result without bariatric surgery.
Sources: en.wikipedia.org
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.
It is shorter than the native hormone and carries a cyclic constraint that improves stability. These changes raise receptor potency and slow breakdown relative to the naturally occurring peptide.
Published accounts date its development to the 1980s, when researchers were generating analogues of melanocyte-stimulating hormone. That work aimed to produce more stable compounds for studying pigmentation biology.
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.