AssayIndex
Melanocortin-receptor peptides

Melanotan II

MT-II · MT2 · Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 · C50H69N15O9 · monoisotopic 1023.5402 Da. The index holds 186 assay reports on this compound across 27 batches from 14 suppliers.

186 reports27 batchesmedian 99.24 %index spec 98.5 %
Section 1

Analytical fingerprint

Hand-authored chemistry. These properties describe the substance and do not change when a record is added.

Melanotan II is a head-to-side-chain lactam cyclic heptapeptide, and the defining impurity is the uncyclised linear precursor at +18 Da, which elutes 0.74 min early. Incomplete cyclisation is the commonest process failure and levels above 1.5 % are a reliable indicator of a rushed macrolactamisation step. The [L-Phe7] diastereomer is mass-identical and matters because the D-Phe configuration is what confers the receptor affinity; RG-2 resolves it to about 60 % valley, which is enough to see but not enough to integrate reliably. Records report it as "co-eluting diastereomer, estimated" where applicable.

Molecular formula
C50H69N15O9
Monoisotopic mass
1023.5402Da
Average mass
1024.18Da
Residues
7
Nominal retention (RG-2, 30 min)
9.84min
Retention window
0.25min
Counter-ion as usually shipped
acetate
Typical label claims
10 mg
Analytical difficulty (index scale)
0.90 — straightforward
Purity is a defined quantity
YES
Section 2

Representative chromatogram

Drawn from this page's own medians. Not a scan, not an illustration, and not any single report.

027235447817010894 Melanotan II9.84 min · 99.24 % 9.1012.19 same trace · ×200 vertical expansion, baseline-corrected · main peak off-scale reporting threshold 0.05 % area 05101520253035 Retention time (min) Response (mAU)
Figure 1. A representative Melanotan II trace on the index reference method RG-2, constructed from this page's own numbers: the main peak carries the index median purity of 99.24 % area at the nominal retention time of 9.84 min, and each impurity peak carries the median area the index has observed for that named species at its characteristic retention offset. It is not a scan of any single report — every individual record's own chromatogram is on its own page. The lower panel is the same trace at a stated vertical expansion, baseline-corrected, so the impurities are visible; the main peak runs off-scale there by design. Baseline noise is seeded from the compound slug.
Section 3

What the index has observed

Arithmetic over the 186 records the index holds. Aggregates on this page are computed over the records the index holds, which are not a random sample of the material on the market. Lots that get tested are lots someone chose to test. Read every figure here as a description of this dataset rather than as an estimate of a population.

Median purity 99.24% n=186
Interquartile range 0.89pp n=186
Minimum 96.85% n=186
Maximum 99.93% n=186
Pass rate vs spec 84.9% n=186
Median recovery vs claim 97.4% n=117
Median water 4.53% n=186
Median |mass error| 2.2ppm n=151
012243692.093.094.095.096.097.098.099.0100.092.00–92.25 %: n=092.25–92.50 %: n=092.50–92.75 %: n=092.75–93.00 %: n=093.00–93.25 %: n=093.25–93.50 %: n=093.50–93.75 %: n=093.75–94.00 %: n=094.00–94.25 %: n=094.25–94.50 %: n=094.50–94.75 %: n=094.75–95.00 %: n=095.00–95.25 %: n=095.25–95.50 %: n=095.50–95.75 %: n=095.75–96.00 %: n=096.00–96.25 %: n=096.25–96.50 %: n=096.50–96.75 %: n=096.75–97.00 %: n=197.00–97.25 %: n=097.25–97.50 %: n=097.50–97.75 %: n=397.75–98.00 %: n=198.00–98.25 %: n=498.25–98.50 %: n=1998.50–98.75 %: n=1798.75–99.00 %: n=1799.00–99.25 %: n=3299.25–99.50 %: n=2499.50–99.75 %: n=2899.75–100.00 %: n=40median 99.24 Purity (% area) Reports
Figure 2. Purity distribution across all 186 Melanotan II records. Dashed line is this compound's median (99.24 %); the solid vertical is the index acceptance specification for the melanocortin-receptor peptides class (98.5 %). Domain is fixed at 92–100 % on every purity histogram on this site so that compounds can be compared by eye — a wide distribution here is a hard compound, a narrow one is an easy one, and neither is a statement about the suppliers.
Section 4

By supplier

Suppliers with fewer than two purity records on this compound are omitted from the figure rather than drawn as a line. The full table, including the thin cells, is on the by-supplier page.

96.697.297.898.499.099.6100.2SWBSWB: Q1 99.18, median 99.46, Q3 99.80, n=38outlier 98.25n=38HomopeptideHomopeptide: Q1 99.01, median 99.26, Q3 99.73, n=37n=37GGPepsGGPeps: Q1 98.45, median 99.23, Q3 99.52, n=16n=16SGNSGN: Q1 98.34, median 98.62, Q3 98.94, n=16outlier 96.85n=16TFCTFC: Q1 99.02, median 99.33, Q3 99.69, n=14n=14KPKP: Q1 98.16, median 98.36, Q3 98.42, n=11outlier 97.61outlier 97.64outlier 98.82n=11QYBQYB: Q1 99.61, median 99.87, Q3 99.93, n=11n=11MKMMKM: Q1 98.48, median 98.66, Q3 98.83, n=7outlier 97.64n=7WWBWWB: Q1 99.48, median 99.54, Q3 99.72, n=7outlier 99.08n=7CPCCPC: Q1 98.73, median 99.07, Q3 99.27, n=6n=6WXTWXT: Q1 99.02, median 99.09, Q3 99.64, n=6n=6QSCQSC: Q1 99.44, median 99.79, Q3 99.92, n=6n=6SSASSA: Q1 98.39, median 98.59, Q3 99.02, n=6n=6JEEPJEEP: Q1 99.56, median 99.57, Q3 99.77, n=5outlier 99.08n=5 Purity (% area)
Figure 3. Melanotan II purity by supplier, ordered by coverage. The vertical line is the index acceptance specification. Boxes that overlap are suppliers this dataset cannot separate, and most of them overlap.

Full per-supplier table with n= caveats →

Section 5

Characteristic impurities and degradants

The left three columns are authored chemistry — what this molecule characteristically carries and where it elutes. The right three are what the index has actually reported.

Named speciesΔRT (min, RG-2)Δ mass (Da)Seen inMedian % areaMax % area
[L-Phe7]-diastereomer-0.16mass-identical92%0.080.98
linear (open-lactam) precursor (+18 Da)-0.74+18.01191%0.211.19
oxidised Trp (+16 Da)-0.36+15.99587%0.092.11
des-acetyl MT-II (−42 Da)-0.48-42.01185%0.091.14
MT-II dimer (head-to-tail)+2.35+1023.54071%0.060.82

Degradation pathways

  • Trp oxidation
  • lactam hydrolysis reopening the ring

Full impurity profile, with what each named species implies about the synthesis →

Section 7

Quarterly coverage

QuarterReportsMedian purityRange
2024-Q1399.7099.35–99.88
2024-Q22499.5698.65–99.93
2024-Q31n<3—
2024-Q40n<3—
2025-Q12999.5698.24–99.93
2025-Q20n<3—
2025-Q31598.3697.61–99.93
2025-Q43199.0897.64–99.93
2026-Q14099.3398.33–99.93
2026-Q22298.9496.85–99.80
2026-Q32199.3598.25–99.86

Quarter-by-quarter detail →

Section 8

Most recent records

The 25 most recent Melanotan II records of 186.
ReportSupplierLotLabQuarterPurity %Water %Recovery %ProvenanceFlagsResult
AX-2026-042648GGPepsGGPE-2603-P8735Janoshik2026-Q399.106.97—Supplier-supplied4MARGINAL
AX-2026-042479SWBSWB-2603-A5707Janoshik2026-Q399.163.6794.5Supplier-supplied1MARGINAL
AX-2026-042481SWBSWB-2603-A5707Medutest2026-Q398.953.3790.8Supplier-supplied1MARGINAL
AX-2026-042650GGPepsGGPE-2603-P8735Medutest2026-Q399.866.49—Supplier-supplied3MARGINAL
AX-2026-042483SWBSWB-2603-A5707Janoshik2026-Q399.383.73107.2Supplier-supplied1MARGINAL
AX-2026-042651GGPepsGGPE-2603-P8735PeptideMeter2026-Q399.537.0490.7Supplier-supplied4MARGINAL
AX-2026-042478SWBSWB-2603-A5707VendorInvestigate2026-Q398.734.34—Buyer-sourced1MARGINAL
AX-2026-042482SWBSWB-2603-A5707Janoshik2026-Q399.224.66—Supplier-supplied1MARGINAL
AX-2026-042652GGPepsGGPE-2603-P8735Janoshik2026-Q399.366.96—Supplier-supplied4MARGINAL
AX-2026-042646GGPepsGGPE-2603-P8735Janoshik2026-Q399.807.0497.3Supplier-supplied3MARGINAL
AX-2026-042472SWBSWB-2603-A5707Janoshik2026-Q399.554.28—Supplier-supplied0PASS
AX-2026-042475SWBSWB-2603-A5707Janoshik2026-Q399.424.21105.7Supplier-supplied0PASS
AX-2026-042647GGPepsGGPE-2603-P8735Janoshik2026-Q399.487.06—Supplier-supplied4MARGINAL
AX-2026-042645GGPepsGGPE-2603-P8735VendorInvestigate2026-Q398.327.12—Buyer-sourced3FAIL
AX-2026-042480SWBSWB-2603-A5707Janoshik2026-Q399.034.05—Supplier-supplied1MARGINAL
AX-2026-042476SWBSWB-2603-A5707VendorInvestigate2026-Q398.253.86—Buyer-sourced1FAIL
AX-2026-042484SWBSWB-2603-A5707PeptideMeter2026-Q398.903.53101.5Buyer-sourced1MARGINAL
AX-2026-042474SWBSWB-2603-A5707Medutest2026-Q399.354.29—Supplier-supplied1MARGINAL
AX-2026-042649GGPepsGGPE-2603-P8735PeptideMeter2026-Q399.537.32105.6Supplier-supplied4MARGINAL
AX-2026-042473SWBSWB-2603-A5707PeptideMeter2026-Q399.373.7596.4Supplier-supplied1MARGINAL
AX-2026-042477SWBSWB-2603-A5707Medutest2026-Q398.874.52103.6Buyer-sourced1MARGINAL
AX-2026-043240SGNSGN-2602-L1809PeptideMeter2026-Q298.652.87—Supplier-supplied2MARGINAL
AX-2026-041887JEEPJEEP-2604-R3923Janoshik2026-Q299.565.0595.2Supplier-supplied0PASS
AX-2026-043242SGNSGN-2602-L1809VendorInvestigate2026-Q298.142.18107.2Buyer-sourced1FAIL
AX-2026-041890JEEPJEEP-2604-R3923Medutest2026-Q299.805.06107.4Supplier-supplied1FAIL