In short
Nootkatone is the sesquiterpene ketone that gives grapefruit much of its character. It is produced from valencene or by fermentation as well as isolated, and adds a juicy, woody grapefruit note.
What Nootkatone smells like
Nootkatone is the bitter, woody grapefruit molecule. A Bedoukian sheet describes a bright, characteristically grapefruit odour with woody, slightly herbal and fruity aspects; a glossary a sharp, bitter-zesty peel over a dry cedarwood floor. It occurs in grapefruit peel oil at a fraction of a percent yet supplies much of grapefruit's bitter, woody character, and, unlike the citrus terpenes, it lasts for days. Commercial nootkatone is mostly made from valencene.
- Leading note
- Grapefruit peel
- Clear facets
- Bitter, woody
- Faint facets
- Herbal
- Character
- Bitter, dry, tenacious, bright
What makes Nootkatone distinctive
It is grapefruit's bitterness and woodiness without its juice — and a citrus impression that outlasts the monoterpenes many times over.
Where the descriptions disagree: An older journal review describes it as sweet and citrusy; trade sources stress bitterness. Reported strength and blotter life vary widely between suppliers.
How Nootkatone is used
Used to give grapefruit character and citrus persistence to compositions, and in grapefruit flavours.
Typical role: modifier (used in small amounts to change the character of a blend); fixative (slow to evaporate; helps a blend last and holds lighter notes).
How Nootkatone differs from similar materials
- Valencene
- Valencene, its usual starting material, is sweet orange; nootkatone is bitter, woody grapefruit.
- Grapefruit Oil (Expressed)
- Nootkatone supplies grapefruit oil's bitter, woody note; the oil adds a limonene juiciness and sulphurous trace compounds. (compared directly by a cited source)
- Grapefruit Mercaptan
- Grapefruit mercaptan is the juicy, sulphurous side of grapefruit; nootkatone the bitter, woody peel.
- Methyl Pamplemousse
- Methyl Pamplemousse is a green, juicy, slightly sour grapefruit top; nootkatone is bitter-woody and far more lasting.
An asterisk marks a difference that a cited source states directly. The others compare the published descriptions of each material. Smell varies with grade, supplier and dilution; compare them side by side on blotters before substituting one for another.
Formulation considerations
A crystalline solid at room temperature in pure form; dissolve it before weighing into a formula. IFRA sets a specification for it.
Identity and classification
- Type
- Aroma chemical
- Origin
- Occurs in nature
- Odour family
- Citrus / Woody
- Note position
- Top to heart note
- Physical form at room temperature
- Solid
- CAS number
- 4674-50-4
- Molecular formula
- C15H22O
- Molecular weight
- 218.33 g/mol
- IUPAC name
- (4R,4aS,6R)-4,4a-dimethyl-6-prop-1-en-2-yl-3,4,5,6,7,8-hexahydronaphthalen-2-one
The CAS number, formula and molecular weight are taken from PubChem compound 1268142, whose own record lists this CAS number; checked 19 October 2026.
Safety and compliance
The IFRA Standards Library lists a Standard covering Nootkatone:
- "Nootkatone" — Specification, 40th Amendment, published 2006-01
Limits differ by product category and are set out in the Standard itself; this page does not reproduce them. The list above reflects the library as read on 19 October 2026.
Hazard classification of the neat substance, as PubChem summarises it, read 26 October 2026. Companies notifying the ECHA C&L Inventory classify it (300 reports): H315 causes skin irritation (35.7% of reports); H319 causes serious eye irritation (35.7% of reports); H317 may cause an allergic skin reaction (35.3% of reports). 192 of the reports find it does not meet the hazard criteria. A skin sensitiser classification concerns handling the neat material and the dose in a finished product; the IFRA Standards, where they apply, set the limits. Unless it is harmonised, this is the notifiers' own classification, not a binding one.
This page is general information, not a safety assessment or a specification. Confirm identity, composition, IFRA status and allergen content from your supplier's documents for the lot you hold.
Materials it works with
-
Grapefruit Oil (Expressed)
Essential oil · Citrus / Fruity — citrus, bitter, juicy, sparkling
-
Vetiver Oil
Essential oil · Woody / Green — earthy, smoky, woody, rooty
-
Methyl Pamplemousse
Aroma chemical · Citrus / Green — grapefruit, citrus, green, bitter
-
Cedramber
Aroma chemical · Woody / Amber — woody, amber, dry, cedar
-
Valencene
Aroma chemical · Citrus / Woody — citrus, sweet, woody, orange
Nootkatone is also suggested as a partner on the pages for Grapefruit Mercaptan.
Used in formulas and accords
Used in 4 published formulas
Nootkatone is an ingredient in 4 perfume formulas in the Formula & Accord Library.
RUŌOD House Originals
Original compositions by RUŌOD House.
Further reading
Questions about Nootkatone
Is Nootkatone natural or synthetic?
The molecule occurs in nature. Commercial Nootkatone may be made by synthesis or obtained from natural sources, so check the supplier's specification if the distinction matters to you.
What is the CAS number of Nootkatone?
4674-50-4. It was checked against PubChem on 19 October 2026.
Which published formulas use Nootkatone?
Nootkatone is used in 4 published formulas in the RUŌOD Lab Formula & Accord Library, including Coconut Concrete, Ginger Lightning and Pith & Pepper. Each is listed with a link under "Used in formulas and accords" on this page.
Is Nootkatone covered by an IFRA Standard?
Yes. The IFRA Standards Library lists a Standard covering it: "Nootkatone" — Specification, 40th Amendment. The limits depend on the product category; read the Standard itself before formulating.
Sources
- PubChem — compound 1268142, checked 19 October 2026.
- PubChem — GHS classification (the ECHA C&L Inventory notifications and any harmonised EU entry), read 26 October 2026.
- IFRA — Standards Library, read 19 October 2026.
- Bedoukian Research — Nootkatone Crystals — manufacturer's description.
- Fraterworks — nootkatone crystals — distributor's description.
- Premiere Peau — Nootkatone — published perfumery reference.
- Journal of the Society of Cosmetic Chemists — review of citrus odorants — published literature.
- Olfactory profile: the RUŌOD Lab team's synthesis of the published descriptions above, reviewed 20 October 2026. Evidence: several independent published descriptions, which agree. Classification and the short description: revision 1. Descriptions of odour are judgement, not measurement.