Material guide · 16
Material guide: coumarin — the hay sweetness in tonka and the start of fougere
· 12 min read
CAS 91-64-5, the sweet core of tonka beans and a standard material in fougere perfumery. A white crystal with 364-hour substantivity and 74 suppliers; smell, family and buying stay in one guide.
Leave a freshly cut lawn until evening and the smell turns sweeter and sweeter. That is largely coumarin.
What matters
- Coumarin is the sweetness of new-mown hay: the lead of the tonka bean and one part of the classic fougère structure (lavender + oakmoss + coumarin), a trio that perfume-history lore counts among the starting points of modern perfumery.
- It is a toxicology textbook case: metabolising it produces toxic metabolites in rats and mice, while most humans use a detoxification pathway. It is an often-cited example of why animal results cannot be transplanted directly onto humans.
- But there is a second layer: later human clinical data showed a subgroup of people more susceptible to its liver toxicity, which is why regulators keep a tolerable daily intake. All of this concerns ingested doses (cinnamon, food); perfumery's exposure routes are different, and so are the concerns.
The record
| CAS | 91-64-5 |
| Formula | C₉H₆O₂ |
| MW | 146.15 |
| Odour | sweet, hay, tonka, new-mown hay, coumarinic |
| Odour family | tonka |
| Strength | medium (evaluate at 10% or less) |
| Substantivity | 364 h (at 10% in DPG, on a strip) |
| Flash point | > 93 °C |
| Shelf life | 24 months or longer (cool, dark, sealed) |
| Registers | GRAS, JECFA, IFRA |
Plain reading: CAS is the material's ID number. The 364 hours is one of this series' longest records, but note it was measured on a 10% dilution (most materials' records are neat): coumarin is a crystalline solid at room temperature, so in practice you either pre-dilute or weigh crystals straight into the formula. The first time I ordered it I was half expecting a liquid and got a jar of white crystals. That is also its qualification as a base note: fifteen days later, it is still on the strip.
What it is
Coumarin occurs naturally in tonka beans, cassia cinnamon, sweet clover and other plants. Chemistry-history lore gives it one more title: first synthesised by Perkin in 1868, one of the earliest fragrance molecules made by man, the starting line of the modern perfume industry. In 1882, Houbigant's Fougère Royale used synthetic coumarin, and the fougère ("fern") family took its name from it. That part is also perfume-history lore, much retold, with many versions of the details.
Our database's natural_synthetic field marks it "both": it is in tonka absolute, and the market mainstream is synthetic crystals.
Rodents and humans do not convert directly
Coumarin follows different metabolic routes in rodents and most humans, while human data still identify a more sensitive subgroup. Keep the conclusion here: do not translate one animal result directly into human risk, and do not use species difference to dismiss human evidence. The full case is in How to read fragrance-safety studies.
Smelling it
- Evaluate at 10% or less (the database says so). Since it is a crystal, you will be making a dilution anyway.
- It is the skeleton of "sweet", not the melody: alone it is hay-and-almond sweet; in a formula it binds lavender, vanillin and tobacco notes together.
- Build the fougère trio yourself once: lavender + oakmoss (or its substitutes) + coumarin, in whatever proportions — you will smell where an entire family of perfumes comes from.
- Put it side by side with vanillin. Two sweet bases, one creamy, one like hay.
The catalogue family
| Item | What it is |
|---|---|
| coumarin (74 suppliers) | the material itself: synthetic crystals |
| dihydrocoumarin (55 suppliers) | the hydrogenated version — rounder, herbal-sweet |
| tonka bean absolute (40 suppliers) | the natural source: coumarin plus the bean's full supporting cast |
| 6-methyl coumarin (35 suppliers) | the methylated variant |
| octahydrocoumarin (20 suppliers) | the fully hydrogenated version |
| tonka bean resinoid (9 suppliers) | the thick solvent-extracted version |
Regulatory
Listed on GRAS, JECFA, IFRA. As always, registers carry no limit values. Two practical facts worth knowing: coumarin is one of the fragrance allergens that EU cosmetics regulation requires to be named on the label (above a threshold it must appear in the ingredient list), and the tonka bean itself is banned as a food ingredient in the United States because of its coumarin content, which is why "tonka" flavours in American desserts are always coy. For skin formulae, consult the current IFRA Standards and the supplier's specification.
Buying it
- Buy crystals and make your own 10% dilution. Crystals are cheap and stable; the dilution is what you will actually reach for day to day.
- If you want the natural version's complexity, add tonka bean absolute. Smell the two side by side and you will hear the difference between "molecule" and "plant", one more example for the batch variation article.
- A 364-hour-class base note wants a light hand. It will stay to the end.
→ Coumarin in the database: full properties, supplier list, suggested pairings. → Tonka bean absolute | Dihydrocoumarin | Search by odour: try "hay sweet" for its neighbours.
References
B. G. Lake, Coumarin metabolism, toxicity and carcinogenicity: relevance for human risk assessment, Food and Chemical Toxicology, 37(4), 423–453 (1999). PMID 10418958
K. Abraham, F. Wöhrlin, O. Lindtner, G. Heinemeyer & A. Lampen, Toxicology and risk assessment of coumarin: focus on human data, Molecular Nutrition & Food Research, 54(2), 228–239 (2010). PMID 20024932