If you have been reading about cyclic heptapeptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
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 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.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analogue of alpha-melanocyte-stimulating hormone |
| Common synonyms | MT-II; melanotan 2 | No internationally accepted non-proprietary name |
| Typical presentation | Lyophilised powder in a sealed vial | Often supplied alongside a separate diluent |
| Regulatory status | Unapproved therapeutic substance | Customs seizure reported in several jurisdictions |
| Reported route in use | Subcutaneous injection | Self-administered outside clinical settings |
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.
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.
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.
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.
== Etiology == The etiology of anxiety disorder remains unknown. There are several contributing factors that are yet to be proved to cause anxiety disorders. These factors include childhood anxiety, drug induction by central stimulant drugs, metabolic diseases or having depressive disorder.
=== Thailand === Thailand has been severely impacted by the crisis. Thailand imports 57% of its oil from the Middle East, which requires to pass the Strait of Hormuz. The diesel fuel price has increased from 29.94 THB per litre in February, up to peak price of 50.54 THB per litre in 7 April. The government froze diesel prices at 29.94 THB per litre in the first 15 days of the crisis, and has directed people to raise their air-conditioning temperatures and reduce their outer clothing, to reduce energy consumption, and employees of all government agencies are working from home. Phipat Ratchakitprakarn, Deputy Prime Minister of Thailand and co-owner of PTG Energy (branded as PT), one of the largest oil companies in Thailand, was assigned by Anutin Charnvirakul, Prime Minister of Thailand to control and mitigate the impact of fuel crisis in Thailand. He has been criticised by Thai citizens for his failure to manage the impact, and the "Ban PT" movement has gained traction across the internet. In Pathum Thani Province, north of Bangkok, the local Provincial Administrative Organization (PAO) has terminated its 4.45 satang per litre (Equivalent to 0.445 THB) fuel dispenser tax for 3 months, in 317 stations across the province. Normally, this tax generates 4 million THB per month for the PAO. By this measure the PAO hopes to reduce fuel costs for the residents of Pathum Thani Province, especially for farmers.
== Sources == Kahn, Charles H. (2001). Pythagoras and the Pythagoreans: A Brief History. Indianapolis, Indiana and Cambridge, England: Hackett Publishing Company. ISBN 978-0-87220-575-8. OCLC 46394974 – via Internet Archive. Varasdi, J. Allen (1996). Myth Information. New York: Ballantine Books. ISBN 0-345-41049-1.
Sources: en.wikipedia.org
Eastern Cuba, and particularly Oriente Province, with its cultural epicentre at Santiago de Cuba, was for most of Cuba's history culturally distinct from Western Cuba and the city of Havana. Debates between Catholics, Protestants, and Secularists stirred further divisions. When the Cuban identity was being developed as distinct from a Spanish colony, hot debates between autonomists and separatists took place in the Cuban Masonic Lodges. The issue of slavery was hotly debated within all secret societies, not only in Cuba, but in the entire Caribbean and the Gulf of Mexico, and especially within the societies of Freemasonry in Latin America. Views on slavery would prove to quickly cause a strife between two very different brands of Freemasonry that developed in Cuba. The brand of Freemasonry that eventually won-over in Cuba was pro-independence and anti-slavery, conjoined with a prevailing current of Spanish liberal constitutionalism.
US pathology firm CPL-Clinical Pathology Laboratories for $US123.5 million (A$121.5 million). In 2010, Sonic Healthcare acquired Labor Lademannbogen (Hamburg, Germany) and Medhold Group (Antwerp, Belgium), and through the IPN the Prime Health Group. In the US, the company acquired CBLPath (Rye Brook, NY) and Physician's Automated Laboratory (Bakersfield, California).
Opioids are a class of drugs that derive from, or mimic, natural substances found in the opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, including pain relief. The terms opioid and opiate are sometimes used interchangeably, but the term opioid is often used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain, while the term opiate is often used to refer to alkaloid compounds naturally found in the opium poppy plant Papaver somniferum. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use disorder, and suppressing cough. The opioid receptor antagonist naloxone is used to reverse opioid overdose. Extremely potent opioids such as carfentanil are approved only for veterinary use. Opioids are also frequently used recreationally for their euphoric effects or to prevent withdrawal. Opioids can be fatal, and have been used, alone and in combination, in a small number of executions in the United States. Side effects of opioids may include itchiness, sedation, nausea, respiratory depression, constipation, and euphoria. Long-term use can cause tolerance, meaning that increased doses are required to achieve the same effect, and physical dependence, meaning that abruptly discontinuing the drug leads to unpleasant withdrawal symptoms. The euphoria attracts recreational use; frequent, escalating recreational use of opioids typically results in addiction.
Sources: en.wikipedia.org
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.
It was developed in the 1980s by researchers investigating analogues of alpha-melanocyte-stimulating hormone for pigmentation and related endpoints. Early work included small human studies during the 1990s. Development did not progress to licensing, and the compound remained a research and grey-market item.
Peptides are prone to truncation, oxidation and aggregation during synthesis and handling. Without independent testing, a buyer cannot confirm the identity or the content of a vial. Analytical surveys of unapproved peptide products have repeatedly found discrepancies between label claims and measured composition.
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.