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Melatonin

Melatonin is an indoleamine, N-acetyl-5-methoxytryptamine, first isolated from bovine pineal glands. It is made in the pineal gland and several peripheral tissues; commercial material is synthetic.

Melatonin testing at Vanguard Laboratory: purity, quantity and identity from $250 per sample. Results in 3 to 5 business days; sterility 14 days.

Full USP monograph testing is available. See USP Testing.

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On this page: Testing · Compound data · Structure and names · Research · Analytical notes · USP–NF · References

Tests and prices

Purity and quantity

$250

Chromatographic purity and mg per unit by the method matched to the compound, identity against a reference standard. 1 unit.

Raw powder purity

$200

Chromatographic purity on bulk powder. 50 mg.

Add-on tests

Add-on testPrice
Identity and impurities
FTIR identity$90
CHNS elemental analysis (carbon, hydrogen, nitrogen, sulfur)$125
Chiral purity (where a chiral method exists; new methods quoted)$250
Water, solvents and salt form
Water content by Karl Fischer$60
Residual solvents$150
Counterions: chloride, acetate and TFA$70
Assay
Assay, % w/w (with raw powder purity; $250 together)+$50
Metals and conformity
Heavy metals: arsenic, cadmium, chromium, mercury and lead$150
Conformity: purity and quantity on more units from the same lot$100 per extra unit
Microbiology (injectables)
Endotoxin$210
Sterility or bioburden$150
Container closure integrity (CCI)$50
Screening
Fentanyl screen$50

10% off for 10 or more samples.

Need something else? We run other tests on request.

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Testing notes

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TestPurpose for this compoundReported asSampleTurnaround
Purity and quantityAssay against label claim. Related-compound peaks are reported; identifying specific compounds, such as 5-methoxytryptamine, is a separate request.Purity, area percent, two decimals. Quantity, mg per unit, with label claim.1 sample unit; contact the laboratory about quantity for the submitted format.3 to 5 business days from receipt.
IdentityRoutine identity: retention time and UV spectrum against a reference standard. It does not establish stereochemistry.Match or no match, with the basis stated.No additional sample unit.3 to 5 business days, with purity and quantity.
LC-MS identityMass evidence for melatonin; other indoleamines, such as serotonin, are identified on request. Quoted separately.Observed mass, expected mass, mass spectrum.Confirm sample quantity and the compound list before shipping.3 to 5 business days from receipt.
Heavy metalsDietary supplement products are commonly screened for lead, arsenic, cadmium and mercury.Each element with result and detection or quantitation limit.1 extra unit.3 to 5 business days from receipt.
Residual solventsSynthetic raw material may carry process solvents.Each solvent with result and reporting limit.1 additional vial.3 to 5 business days from receipt.
Raw powder purityPurity of the bulk ingredient before encapsulation or tableting.Purity, area percent, two decimals. Chromatogram.50 mg in a sealed container, labeled with material name and lot.3 to 5 business days from receipt.

What these results do not show: results describe the sample tested. Purity and content do not establish biological activity, sterility, or the absence of contaminants that were not tested.

Structure

2D structure of melatonin drawn in Vanguard Laboratory colors

Melatonin: 2D structure drawn from the PubChem record. Stereochemistry shown as registered.

Compound data

Classification

indoleamine (N-acetyl-5-methoxytryptamine)

Formula

C13H16N2O2

Molecular weight

232.28 g/mol (free base; no salt form in common use)
Monoisotopic 232.1212 Da

CAS number

73-31-4

Structure and names

Stereochemistry: achiral (no stereocenters)

CAS note: Free base (neutral molecule).

Other names: N-acetyl-5-methoxytryptamine, N-[2-(5-methoxy-1H-indol-3-yl)ethyl]acetamide, Circadin (EU prolonged-release product)

PubChem CID 896 · UNII JL5DK93RCL[3, 4]

Structural features:

  • Indole ring with 5-methoxy substituent.
  • Ethylamine side chain at C3 carrying an N-acetyl group.
  • Small, neutral, moderately lipophilic molecule; no ionizable group at physiological pH.

Research background

Sold as a dietary supplement in the US[5]; in the EU, prolonged-release melatonin is the active ingredient of the authorised medicine Circadin[6].

  • Melatonin binds two G protein-coupled receptors, MT1 and MT2, encoded by MTNR1A and MTNR1B. (review)[7]
  • High receptor density in the circadian pacemaker links melatonin to the phasing of circadian rhythms. (review)[8]
  • Antioxidant and free radical scavenging properties have been studied and reviewed relative to receptor-mediated actions. (review)[7]

Summaries of published research, for reference only. Not a claim of safety or efficacy.

Analytical considerations

  • Low label claims (often a few mg or less) make accurate assay and unit-to-unit content variation the main quality questions.[9]
  • Gummy, liquid and capsule matrices need an extraction shown to recover melatonin before assay (a method-development consideration).
  • In a 2017 study, serotonin, a related indoleamine, was found in 8 of 31 supplements, and content varied between lots; methods should resolve it from melatonin.[9]
  • Under the conditions studied, degradation in solution depended on pH, temperature and light; standards and sample solutions need controlled handling.[10, 11]
  • A 2023 Waters implementation of the USP method describes resolving melatonin from melatonin related compound A (5-methoxytryptamine) as a suitability requirement.[12]

USP–NF monographs

Melatonin[1]

  • Applies to: dietary supplement ingredient
  • Version: current official USP–NF version at the time of testing
  • Tests in the monograph: assay (definition: NLT 98.5% and NMT 101.5% of C13H16N2O2, dried basis).

Melatonin Tablets[2]

  • Applies to: dietary supplement dosage form
  • Version: current official USP–NF version at the time of testing
  • Tests in the monograph: assay (definition: NLT 90.0% and NMT 110.0% of labeled amount).

Vanguard Laboratory:

  • Identity, assay and related compounds, and tablet assay against label claim. Dissolution testing per USP is available on request.
  • Procedures offered from these monographs: Selected procedures on request, using the current official USP–NF version. Scope and sample quantity are agreed before shipping.
  • Complete monograph testing: Not offered as a package. Selected procedures are run as requested; ask the laboratory about a specific test list.

Related general chapters: 〈2091〉 Weight Variation of Dietary Supplements, 〈2040〉 Disintegration and Dissolution of Dietary Supplements, 〈2232〉 Elemental Contaminants in Dietary Supplements, 〈2021〉 Microbial Enumeration Tests: Nutritional and Dietary Supplements. General chapters describe test methods; they are not compound-specific monographs. Chapters numbered 1000 to 1999, such as 〈1503〉, are informational.

Sample and formulation

  • Common forms are tablets, capsules, gummies, liquids and bulk powder; gummy and liquid matrices complicate extraction.
  • Protect solutions from light and heat during preparation.
  • Report label claim per unit so assay can be expressed as percent of labeled amount.

Related compounds

  • L-tryptophan: precursor
  • Serotonin (5-hydroxytryptamine): precursor
  • Agomelatine: melatonin MT1/MT2 receptor agonist that is also a 5-HT2C antagonist
  • 5-Methoxytryptamine (USP Melatonin Related Compound A): structurally related tryptamine; named as a melatonin related compound in a secondary source

References

  1. [1] United States Pharmacopeia. Melatonin. USP-NF, dietary supplement monographs. doi.usp.org ↑
  2. [2] United States Pharmacopeia. Melatonin Tablets. USP-NF, dietary supplement monographs. doi.usp.org ↑
  3. [3] PubChem. Melatonin, CID 896. pubchem.ncbi.nlm.nih.gov ↑
  4. [4] FDA Global Substance Registration System. Melatonin, UNII JL5DK93RCL. gsrs.ncats.nih.gov ↑
  5. [5] National Center for Complementary and Integrative Health. Melatonin: What You Need To Know. nccih.nih.gov ↑
  6. [6] European Medicines Agency. Circadin (melatonin) EPAR. Authorised 29 June 2007. ema.europa.eu ↑
  7. [7] Jockers R, Delagrange P, Dubocovich ML, et al. Update on melatonin receptors: IUPHAR Review 20. Br J Pharmacol. 2016;173(18):2702-2725. doi.org ↑
  8. [8] Hardeland R, Cardinali DP, Srinivasan V, et al. Melatonin, a pleiotropic, orchestrating regulator molecule. Prog Neurobiol. 2011;93(3):350-384. doi.org ↑
  9. [9] Erland LA, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. J Clin Sleep Med. 2017;13(2):275-281. doi.org ↑
  10. [10] Daya S, Walker RB, Glass BD, et al. The effect of variations in pH and temperature on stability of melatonin in aqueous solution. J Pineal Res. 2001;31(2):155-158. doi.org ↑
  11. [11] Pranil T, Moongngarm A, Loypimai P. Influence of pH, temperature, and light on the stability of melatonin in aqueous solutions and fruit juices. Heliyon. 2020;6(3):e03648. doi.org ↑
  12. [12] Yang J, Rainville PD. Modernizing USP melatonin monograph assay and impurities methods for increased throughput and reduced solvent waste. Waters application note 720007978. 2023. waters.com ↑
  13. [13] Lerner AB, Case JD, Takahashi Y. Isolation of melatonin and 5-methoxyindole-3-acetic acid from bovine pineal glands. J Biol Chem. 1960;235:1992-1997. pubmed.ncbi.nlm.nih.gov

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