Melatonin
A naturally occurring indoleamine hormone produced by the pineal gland, studied for circadian rhythm regulation, sleep timing, and antioxidant effects.
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What is Melatonin?
Melatonin is an indoleamine hormone synthesized primarily by the pineal gland from the amino acid tryptophan via serotonin. Its secretion is tightly regulated by light exposure — rising in the evening as light decreases, peaking during the night, and falling toward morning. This pattern provides the primary hormonal signal coordinating circadian rhythms throughout the body. While the pineal gland is the principal source for systemic circulation, melatonin is also produced in many other tissues including the retina, gastrointestinal tract, and immune cells.
Melatonin is not a peptide — it is a small-molecule indoleamine — but is included in bioactive compound catalogs due to its role in circadian regulation and its connection to other pineal-related compounds (notably Epitalon and Pinealon). The compound is unusual in its regulatory profile, being available as a dietary supplement in the United States while being a prescription medication in most other developed countries including the United Kingdom, European Union, Japan, and Australia. Ramelteon, a synthetic melatonin receptor agonist, is FDA-approved for insomnia in the United States.
Mechanism of action
Melatonin’s mechanisms of action have been investigated across multiple pathways:
- MT1 and MT2 receptor agonism: Melatonin acts primarily through the MT1 and MT2 melatonin receptors expressed in the suprachiasmatic nucleus (the master circadian pacemaker) and various peripheral tissues, with activation producing circadian rhythm phase-shifting and sleep-promoting effects.
- Direct antioxidant activity: The compound has direct antioxidant activity through scavenging of free radicals, particularly hydroxyl radicals and reactive nitrogen species.
- Antioxidant enzyme stimulation: Beyond direct radical scavenging, melatonin stimulates expression and activity of endogenous antioxidant enzymes including superoxide dismutase, glutathione peroxidase, and catalase.
- Immune modulation: Research has documented effects on immune function including cytokine production, immune cell activity, and inflammatory responses, with effects varying by tissue and context.
- Mitochondrial protection: Studies have examined melatonin’s effects on mitochondrial function, with research suggesting protective effects against oxidative damage at the mitochondrial level.
These pathways are characterized in extensive preclinical and human clinical research.
Research applications
Melatonin has been investigated across several research domains, with the most active areas including:
- Sleep disorder research: The most common research application examines effects on delayed sleep phase syndrome, jet lag, and certain other sleep timing disorders. Research suggests effects on sleep onset latency in normal sleep are more modest than commonly believed.
- Jet lag and circadian rhythm research: Well-documented effects on adaptation to time zone changes when administered at appropriate times have made melatonin a research standard for studying circadian rhythm interventions.
- Shift work research: Studies have examined melatonin to facilitate adaptation to non-standard work schedules and the circadian disruption associated with shift work.
- Antioxidant and oxidative stress research: Melatonin is studied in various contexts where oxidative stress is implicated, including neurodegenerative conditions, cardiovascular disease, and aging-related cellular dysfunction.
- Pediatric sleep research: Studies have examined melatonin in pediatric populations including children with autism spectrum disorders and neurological conditions, with research interest in safety profiles and efficacy across developmental contexts.
This compound is intended for laboratory research use only. It has not been approved for human therapeutic use by any regulatory agency.
Storage & reconstitution
Melatonin is stable at room temperature when protected from light and moisture. For long-term storage of lyophilized or powdered melatonin, storage at -20°C protected from light is recommended. Properly stored melatonin remains stable for 24 months or longer.
Once reconstituted with bacteriostatic water for injection or appropriate solvent, melatonin solutions should be stored refrigerated at 2-8°C and used within 28 days. Avoid repeated freeze-thaw cycles, which can accelerate degradation.
Visual inspection should be performed before each use. The reconstituted solution should be clear and colorless to pale yellow. Reject any solution that appears cloudy, has significant discoloration, or contains visible particulate matter.
For step-by-step reconstitution calculations, see our reconstitution calculator.
For laboratory research use only. The compound described on this page is intended exclusively for in vitro research and laboratory experimentation by qualified researchers and is not for human or veterinary use. It is not a drug, food, dietary supplement, or cosmetic, and has not been approved by the FDA, Health Canada, EMA, or any other regulatory authority for the diagnosis, treatment, cure, mitigation, or prevention of any disease or medical condition. The information provided on this page is for educational and reference purposes only and does not constitute medical advice. By accessing this content you confirm that you are a qualified researcher purchasing for legitimate laboratory purposes.