Material guide: omega-pentadecalactone (exaltolide) — a musk that grows in angelica root, and why smelling it faintly may not be your nose

I missed it the first time I counted musks in the corpus.

Across 954 public formulas, this one material is written four different ways:

Name on the formula	Formulas
exaltolide	13
omega-pentadecalactone	8
cyclopentadecanolide	8
macrolide	2

One CAS number, 106-02-5. Merged, that is 31 formulas at a median dose of 3.00%. Counted separately, all four look marginal. Counted together, it is the fourth most common musk in the corpus.

The short version

• Four names, one molecule. Match materials by CAS, not by name.
• It grows in a plant. Angelica root oil contains 0.85%, and the CO₂ extract of angelica seed contains 7.70%. A natural musk need not come from an animal.
• One GHS statement (H302, harmful if swallowed), against six for the nitro musk musk ketone. The macrocyclic-versus-nitro difference is visible on the label.
• Melting point 34 to 38 °C. It is a solid in the bottle and a liquid on skin.
• A 2024 Givaudan study identified OR5A2 as the key receptor for macrocyclic lactones, and found that a single P172L substitution cuts its sensitivity around 50-fold, with homozygous panelists showing 40 to 60 times the sensory detection threshold. If this smells faint to you, that may be genotype rather than insufficient training.

The basics

Trade names	Exaltolide (Firmenich), Macrolide Supra (Symrise)
CAS	106-02-5
Formula	C₁₅H₂₈O₂
Molecular weight	240.39
Type	Natural/synthetic (macrocyclic lactone musk)
Odour	Musk, animal, powdery, natural, fruity, tobacco, coumarinic, heliotrope, licorice
Odour family	musk
Strength	High (evaluate at 10% or below)
Longevity	400 hours @ 10% in DPG (not a neat value)
Appearance	Colourless solid (est)
Melting point	34–38 °C
Boiling point	137 °C @ 2 mmHg
Flash point	> 104 °C
logP	5.80 (est)
Water solubility	0.1484 mg/L @ 25 °C (est)
Natural occurrence	Angelica root oil 0.85%; angelica seed CO₂ extract 7.70%
Assay	98–100%
Storage	36 months or longer; cool, dry, sealed, away from heat and light
Regulatory	FEMA 2840, JECFA 239, CoE, FLAVIS
Suppliers	52
Corpus position	31 formulas (3.2%), median dose 3.00%, range 0.53–22.22%

One molecule, four names

This deserves its own section, because it will make you buy wrong and count wrong.

Exaltolide is Firmenich's trade name, Macrolide Supra is Symrise's, and cyclopentadecanolide and omega-pentadecalactone are two chemical naming conventions for the same sixteen-membered lactone ring.

When I first counted musks, I treated them as four separate materials and none of them made the top ten. Merged, it ranks fourth, behind musk ketone (84 formulas), galaxolide (82) and ethylene brassylate (59).

This is the mirror-image risk of the one-per-slot article. You believe you put in one musk, but if two of your materials happen to be two trade names for the same molecule, you have put in a double dose of one.

It grows in angelica root

The word musk comes from an animal gland, and every musk on the market today is made in a factory. But one thing about this material is rarely mentioned: it occurs in a plant already.

The database records natural occurrence as 0.85% of angelica root oil and 7.70% of the CO₂ extract of angelica seed.

Seven point seven percent is not a trace. If you own angelica seed CO₂, you already own a dilute macrocyclic musk — which also explains the hard-to-place, un-herbal sweetness angelica materials leave in the drydown.

The database note puts it plainly: a true macrocyclic musk, biodegradable.

Why it may smell fainter to you than to someone else

Musk is the most disputed family in perfumery. The same material draws "far too strong" from one person and "I can't smell it at all" from another. In 2024 that got taken apart.

Emter and colleagues at Givaudan, in Chemical Senses, linked receptor activation, genotype and sensory perception across the three human musk receptors — OR5AN1, OR1N2 and OR5A2.

Several results are worth keeping.

The three receptors detect only musks. Among 440 commercial fragrance compounds, all three responded only to musky-smelling ones.

OR5A2 is the key receptor for macrocyclic lactones, and for polycyclic and linear musks. Omega-pentadecalactone is a macrocyclic lactone.

One amino acid makes a factor of fifty. A single P172L substitution reduces OR5A2 sensitivity by around 50-fold. And in people: panelists homozygous for this mutation have around 40 to 60 times higher sensory detection threshold for selective OR5A2 ligands.

For macrocyclic lactones the authors went further, proving OR5A2 the key receptor through a strong correlation between in vitro activation and the in vivo sensory detection threshold.

The division of labour is clear too. OR5AN1 dominates perception of macrocyclic ketones such as muscone and some nitro musks, since panelists with mutant OR5A2 remain equally sensitive to those ligands. OR1N2 appears to be an additional receptor involved in perceiving natural (E)-ambrettolide.

Back at the bench. If this smells faint and you add a second and a third musk to compensate, what you are compensating for may be a gap at the receptor level — and to other people smelling your work, the musk will be excessive. That is one concrete cause of the four-musks mistake, and it is not a training failure.

The practical handling: get someone else to confirm your musk dose. This is one of the few families where your own nose is not enough to settle the question.

The environmental side, honestly

Macrocyclic musks get described as the environmentally sound kind. There is a basis for that, and the basis is weaker than the claim usually is.

Wong and colleagues, in Environmental Science: Processes & Impacts in 2019, investigated synthetic musk compounds in the urban and surrounding environment. They sampled air from wastewater treatment plants, indoor, urban, rural and remote Arctic sites, plus surface waters from urban and rural tributaries and effluents from three treatment plants.

The findings: galaxolide (HHCB) and tonalide (AHTN) were the two most abundant in air, tributaries and effluents, with six polycyclic musks ranking treatment-plant on-site > indoor > urban > plant off-site > rural. No synthetic musks were found in remote Arctic air, indicating low potential for long-range atmospheric transport. None were found in soils either, likely because of high volatility and fast biodegradation. Trace levels of the toxic nitro musks — musk xylene and musk ketone — were detected in on-site plant air.

And macrocyclic musks accounted for around 10% of the total synthetic musks measured.

Read that number carefully. Ten percent is a share of what was detected, not a ranking of harm. It reflects usage volume and measurability combined, and the study made no toxicity comparison.

What can be stated is the database column: omega-pentadecalactone carries one GHS statement, H302, harmful if swallowed, with acute toxicity at oral rat LD50 above 5,000 mg/kg and dermal rabbit LD50 above 5,000 mg/kg. Set against the six hazard statements in the musk ketone article, the difference shows up on the label.

That 400 hours, again

"400 hours @ 10% in DPG".

As with musk ketone and ethyl vanillin, this is a diluted value, not a neat one — and diluted harder, at 10%. Four hundred hours is the ceiling of the source scale, so passing it at a 10% dilution means the real figure is well past what that scale can record.

Two handling details

One: solid at room temperature, liquid on skin. The melting point of 34 to 38 °C falls between room and body temperature. In the bottle it is a white solid, so weighing means a warm water bath or a stock solution; on skin it is liquid.

Two: it is essentially insoluble in water. Water solubility is 0.1484 mg/L. We measured the starter palette's median at 100 mg/L, so this is about one seven-hundredth of that. Any water-containing product — body mist, hair perfume — needs checking for whether it drops out.

The logP of 5.80 is the same fact written another way.

When you smell it

• Make a 10% stock. The strength field says high, evaluate at 10% or below, and it is a solid; both reasons point the same way.
• Start at 3%. That is the corpus median. The range of 0.53% to 22.22% is wide, and the top end is formulas built around it.
• There is more in there than musk. Past musk, animal and powdery, the odour field carries fruity, tobacco, coumarinic, heliotrope and licorice. The dry, sweet quality it brings to the base is not your imagination.
• Smell it with someone else. The receptor study above is the reason.

Buying and storage

Fifty-two suppliers. Buy on CAS 106-02-5, since at least four names for it circulate. Assay 98–100%.

Shelf life is 36 months or longer, and the flash point above 104 °C removes fire concerns from storage. It is a solid, so sealing against moisture is enough.

Regulatory and safety

One GHS statement: H302, harmful if swallowed. Precautions are washing skin thoroughly after handling, not eating, drinking or smoking while using it, and calling a poison centre if swallowed.

Acute toxicity: oral rat LD50 > 5,000 mg/kg, dermal rabbit LD50 > 5,000 mg/kg, inhalation not determined.

Flavour listings are comprehensive (FEMA 2840, JECFA 239, CoE, FLAVIS). For use limits, check current IFRA Standards — here is how.

→ Omega-pentadecalactone in the database: full physical data, 52 suppliers and suggested blends. → Search by odour: try "musk powdery animal".

References

R. Emter, C. Merillat, S. Dossenbach, A. Natsch, The trilogy of human musk receptors: linking receptor activation, genotype, and sensory perception, Chemical Senses, 49, bjae015 (2024). PMID 38591752. doi:10.1093/chemse/bjae015

F. Wong et al., Urban sources of synthetic musk compounds to the environment, Environmental Science: Processes & Impacts, 21(1), 74–88 (2019). PMID 30575830. doi:10.1039/c8em00341f