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.
Last reviewed on 2026-06-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or oxidised impurities. Mass spectrometry, most often coupled to liquid chromatography, confirms molecular mass and detects substitutions that chromatography alone may miss. Amino acid analysis and peptide mapping supply additional structural evidence, while nuclear magnetic resonance is reserved for full structural confirmation. Laboratories that examine samples sold online report wide variation in actual content, with some vials containing little or none of the labelled material.
| 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 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.
The peer-reviewed record is dominated by small early-phase studies, case reports and pharmacovigilance summaries rather than large randomised trials. Papers typically examine tanning response, receptor selectivity or patterns of reported adverse events. Many note that participants obtained the peptide outside a clinical setting, which limits verification of composition and administered amount. Reported events vary widely, and causality is frequently unclear because the identity and purity of self-sourced material are unknown. Open questions include whether repeated melanocortin receptor stimulation produces cumulative effects, and how often label claims match actual content.
Identification in laboratories relies on reversed-phase liquid chromatography coupled with tandem mass spectrometry, with product-ion spectra compared against a certified reference standard. High-resolution mass spectrometry supplies accurate mass confirmation, and peptide mapping after enzymatic digestion separates melanotan II from closely related analogues. Quantitation of seized material is complicated by unknown counter-ions and residual trifluoroacetate left from purification. Immunoassays raised against alpha-melanocyte-stimulating hormone can cross-react, so chromatographic confirmation is normally required. Urinary detection windows are short, and reported limits of detection differ substantially between laboratories.
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.
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.
planifolia seeds this way are Eulaema polychroma and Scaptotrigona subobscuripennis. Seeds being distributed by bees is a rare behavior and has only been documented in three species of tropical trees previously, the cadaghi (Corymbia torelliana), Coussapoa asperifolia subsp. magnifolia, and Zygia racemosa. Both rodents and marsupials are confirmed to consume fallen pods on the forest floor. Specific species observed eating the pods include Tome's spiny rat (Proechimys semispinosus) and the common opossum (Didelphis marsupialis). Further experiments by a team led by Dr. Adam Karremans showed that the seeds remained viable after being passed through the mammalian gut, but it did not increase or decrease germination significantly.
Consequently, it is often abundant in areas affected by agricultural runoff, bird perches, and atmospheric nitrogen deposition, where nutrient enrichment can alter lichen community structures by reducing acid-sensitive species. Bird guano, which is rich in the toxic compound urea, generally excludes most lichens from these habitats; however, X. parietina achieves one of the highest nitrogen contents reported, partly because of its high urease activity that converts urea into CO2 and NH4.
== Medical uses == Ixazomib is used in combination with lenalidomide and dexamethasone for the treatment of multiple myeloma in adults after at least one prior therapy. There are no experiences with children and youths under 18 years of age. The study relevant for approval included 722 people. In this study, ixazomib increased the median time of progression-free survival from 14.7 months (in the placebo+lenalidomide+dexamethasone study arm including 362 people) to 20.6 months (under ixazomib+lenalidomide+dexamethasone, 360 people), which was a statistically significant effect (p = 0.012). 11.7% of patients in the ixazomib group had a complete response to the treatment, versus 6.6% in the placebo group. Overall response rate (complete plus partial) was 78.3% versus 71.5%. A phase 3 study demonstrated a significant improvement in progression-free survival (PFS) with ixazomib-lenalidomide-dexamethasone (IRd) compared with placebo. High-risk cytogenetic abnormalities were defined as del(17p), t(4;14), and/or t(14;16); additionally, patients were assessed for 1q21 amplification. Of 722 randomized patients, 552 had cytogenetic results; 137 (25%) had high-risk cytogenetic abnormalities and 172 (32%) had 1q21 amplification alone. PFS was improved with IRd versus placebo in both high-risk and standard-risk cytogenetics subgroups: in high-risk patients, with median PFS of 21.4 versus 9.7 months; in standard-risk patients, with median PFS of 20.6 versus 15.6 months.
Sources: en.wikipedia.org
=== Mechanism of action === While it is unclear how fluoxetine exerts its effect on mood, it has been suggested that fluoxetine elicits an antidepressant effect by inhibiting serotonin reuptake in the synapse by binding to the reuptake pump on the neuronal membrane to increase serotonin availability and enhance neurotransmission. Over time, this leads to a downregulation of pre-synaptic 5-HT1A receptors, which is associated with an improvement in passive stress tolerance, and delayed downstream increase in expression of brain-derived neurotrophic factor, which may contribute to a reduction in negative affective biases. Norfluoxetine and desmethylfluoxetine are metabolites of fluoxetine and also act as serotonin reuptake inhibitors, increasing the duration of action of the drug. Prolonged exposure to fluoxetine changes the expression of genes involved in myelination, a process that shapes brain connectivity and contributes to symptoms of psychiatric disorders. The regulation of genes involved with myelination is partially responsible for the long-term therapeutic benefits of chronic SSRI exposure.
== Further reading == Carruthers JD, Fagien S, Joseph JH, Humphrey SD, Biesman BS, Gallagher CJ, et al. (January 2020). "DaxibotulinumtoxinA for Injection for the Treatment of Glabellar Lines: Results from Each of Two Multicenter, Randomized, Double-Blind, Placebo-Controlled, Phase 3 Studies (SAKURA 1 and SAKURA 2)". Plastic and Reconstructive Surgery. 145 (1): 45–58. doi:10.1097/PRS.0000000000006327. PMC 6940025. PMID 31609882. Solish N, Carruthers J, Kaufman J, Rubio RG, Gross TM, Gallagher CJ (December 2021). "Overview of DaxibotulinumtoxinA for Injection: A Novel Formulation of Botulinum Toxin Type A". Drugs. 81 (18): 2091–2101. doi:10.1007/s40265-021-01631-w. PMC 8648634. PMID 34787840.
2002: Anthony Ler Wee Teang was hanged on 13 December 2002 for hiring a teenager to murder his wife. 2003: Kanesan Ratnam, a prisoner who killed his cellmate Shankar Suppiahmaniam by strangulation at Queenstown Remand Prison. Kanesan, who was in remand for a charge of rape, was sentenced to death and later hanged on 10 January 2003. 2004: Soosainathan Dass Saminathan, a jobless Singaporean found guilty of murdering a six-month-old Indonesian baby girl after he raped her. He was hanged on 21 May 2004. 2006: Took Leng How, a Malaysian hanged on 3 November 2006 for the 2004 murder of an eight-year-old girl. 2008: Mohammed Ali bin Johari was hanged on 19 December 2008 for the 2006 rape and murder of his stepdaughter. 2011: Nakamuthu Balakrishnan, a Singaporean sentenced to death for murdering a lorry driver during a S$1.3 million mobile phone heist. His date of death was 8 July 2011. 2014: Wang Zhijian, a Chinese national sentenced to death in 2012 for the 2008 Yishun triple murders. The Court of Appeal dismissed his appeal in 2014 and he was hanged on 20 May 2016 along with Kho Jabing. 2015: Muhammad Kadar, an odd-job labourer charged with knifing a 69-year-old housewife 110 times and therefore killed her during a robbery in 2005. He was hanged ten years later on 17 April 2015. 2016: Kho Jabing, a Malaysian hanged on 20 May 2016 for the 2008 robbery and murder of a construction worker. Wang Zhijian the perpetrator of the 2008 Yishun Triple Murders was also executed together with him.
Sources: en.wikipedia.org
Hydrazine reflux is commonly used for reducing SLGO to SLG(R), but titrations show that only around 20–30% of the carboxylic groups are lost, leaving a significant number available for chemical attachment. Analysis of SLG(R) generated by this route reveals that the system is unstable and using a room temperature stirring with hydrochloric acid (< 1.0 M) leads to around 60% loss of COOH functionality. Room temperature treatment of SLGO with carbodiimides leads to the collapse of the individual sheets into star-like clusters that exhibited poor subsequent reactivity with amines (c. 3–5% conversion of the intermediate to the final amide). It is apparent that conventional chemical treatment of carboxylic groups on SLGO generates morphological changes of individual sheets that leads to a reduction in chemical reactivity, which may potentially limit their use in composite synthesis. Therefore, chemical reaction types have been explored. SLGO has also been grafted with polyallylamine, cross-linked through epoxy groups. When filtered into graphene oxide paper, these composites exhibit increased stiffness and strength relative to unmodified graphene oxide paper. Full hydrogenation from both sides of the graphene sheet results in Graphane, but partial hydrogenation leads to hydrogenated graphene. Similarly, both-side fluorination of graphene (or chemical and mechanical exfoliation of graphite fluoride) leads to fluorographene (graphene fluoride), while partial fluorination (generally halogenation) provides fluorinated (halogenated) graphene.
=== Protein cleavage === Cyanogen bromide hydrolyzes peptide bonds at the C-terminus of methionine residues. This reaction is used to reduce the size of polypeptide segments for identification and sequencing.
Slavery was widespread in Africa, which pursued both internal and external slave trade. In the Senegambia region, between 1300 and 1900, close to one-third of the population was enslaved. In early Islamic states of the western Sahel, including Ghana, Mali, Segou, and Songhai, about a third of the population were enslaved. In European courtly society, and European aristocracy, black African slaves and their children became visible in the late 1300s and 1400s. Starting with Frederick II, Holy Roman Emperor, black Africans were included in the retinue. In 1402 an Ethiopian embassy reached Venice. In the 1470s black Africans were painted as court attendants in wall paintings that were displayed in Mantua and Ferrara. In the 1490s black Africans were included on the emblem of the Duke of Milan. During the trans-Saharan slave trade, slaves from West Africa were transported across the Sahara desert to North Africa to be sold to Mediterranean and Middle eastern civilizations. During the Red Sea slave trade, slaves were transported from Africa across the Red Sea to the Arabian Peninsula. The Indian Ocean slave trade, sometimes known as the east African slave trade, was multi-directional. Africans were sent as slaves to the Arabian Peninsula, to Indian Ocean islands (including Madagascar), to the Indian subcontinent, and later to the Americas. These traders captured Bantu peoples (Zanj) from the interior in present-day Kenya, Mozambique and Tanzania and brought them to the coast. There, the slaves gradually assimilated in rural areas, particularly on Unguja and Pemba islands.
By 1954, the United States was producing 910 t (2 million lb) of antibiotics each year, of which 220 t (490,000 lb) was going into animal feed; in the 1990s, the United States was producing 23,000 t (50 million lb) of antibiotics per year, of which half was going to livestock. The largest user remained the poultry industry, which consumed 4,800 t (10.5 million lb) of antibiotics each year, compared to 4,700 t (10.3 million lb) for hogs and 1,700 t (3.7 million lb) for cattle. A 1981 study by the Council for Agricultural Science and Technology estimated that banning their use in animal feed could cost American consumers up to $3.5 billion a year (equivalent to $12.39 billion in 2025) in increased food prices. The story was similar in the UK, where 44 per cent of antibiotic production was consumed by animals by 1963. By the mid-1950s, there were reports in the United States that milk was not curdling to make cheese. The FDA found that the milk was contaminated with penicillin, which was killing the bacteria required for cheesemaking. In 1963, the WHO reported high levels of penicillin in milk worldwide. People who were allergic to penicillin could now get a reaction from drinking milk. A committee chaired by Lord Netherthorpe was established in the UK in 1960 to inquire into the use of antibiotics in animal feed. In 1962, the committee recommended that restrictions on the use of antibiotics in animals be relaxed.
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.
The lyophilised solid is best kept cold, dry and dark, typically at minus twenty degrees Celsius. Moisture and repeated warming cycles are the main causes of degradation. Solutions prepared from the powder are less stable and are normally used quickly.