Nootkatone (CAS 4674-50-4) — Citrus Top to Heart Note Fragrance Ingredient
Nootkatone
CAS 4674-50-4
What Is Nootkatone?
Nootkatone is a rare aromatic compound that gives grapefruit its distinctive citrusy-woody scent. While found naturally in grapefruit peel and Alaskan yellow cedar, most fragrance applications use the synthetic version. It’s encountered in premium citrus colognes and modern woody fragrances. This ingredient matters because it bridges citrus freshness with woody depth, allowing perfumers to create complex, evolving scents. Its natural scarcity makes synthetic production essential for consistent fragrance applications.
Safety Profile
GENERALLY SAFEWhat Does Nootkatone Smell Like?
Nootkatone bursts with an initial grapefruit-like sparkle – crisp, slightly bitter citrus with a juicy freshness. Within minutes, this evolves into a fascinating woody character reminiscent of freshly split cedar planks, with a dry, almost peppery edge. The dry-down reveals earthy undertones and a subtle muskiness that lingers close to skin. Unlike typical citrus notes that vanish quickly, nootkatone’s tenacity allows it to serve as both top and heart note, creating a seamless transition from bright opening to woody warmth.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Nootkatone provides the grapefruit illusion in this mint-forward fragrance, adding naturalistic citrus depth without the volatility of actual citrus oils.
Used as a bridge between top citrus notes and base woods, nootkatone creates the perfume’s signature ‘wet cedar’ accord.
2D Molecular Structure
SMILES: C[C@@H]1CC(=O)C=C2CC[C@H](C[C@@]12C)C(C)=C
Chemistry, Properties & Perfumer Guide
The Chemistry
Nootkatone is a sesquiterpenoid belonging to the valencene family, structurally related to beta-caryophyllene. While naturally occurring in grapefruit and certain conifers, commercial production typically involves the oxidation of valencene derived from orange oil or through biotechnological synthesis. The molecule’s stereochemistry is crucial – only the (+)-enantiomer exhibits the characteristic grapefruit aroma. Modern production methods often use engineered yeast strains for sustainable production, as isolation from natural sources yields less than 0.1% from grapefruit peel.
Physical & Chemical Properties
| Boiling Point | ~300 °C (estimated) |
|---|---|
| XLogP | 4.1 (predicted) |
| Appearance | Pale yellow viscous liquid |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Used for citrus-woody bridge effects |
| Functional Fragrance | 0.01-0.1% | Up to 0.3% | Adds premium citrus character to detergents |
Classic Accords
Tip: Use nootkatone to extend citrus top notes into woody heart accords, reducing the need for harsh citrus aromachemicals.
Alternatives & Comparisons
The precursor to nootkatone, offering similar woody-citrus character but less intense and more orange-like.
A synthetic grapefruit replacer when only the bright citrus aspect is needed without woody depth.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions under Amendment 51 (2022).
RIFM Assessment
RIFM assessment completed in 2018 – no safety concerns at current usage levels.
Sustainability
As natural extraction from grapefruit is extremely inefficient (requiring ~400kg of peel for 1kg nootkatone), most production now uses biotech methods. Leading manufacturers employ fermentation using engineered yeast strains feeding on agricultural byproducts. This sustainable approach reduces land use compared to citrus farming while avoiding petroleum-derived synthesis routes. The molecule’s potency means small quantities suffice, reducing environmental load in finished products.
Explore Nootkatone
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781439847503
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorLayer 3 · Practical
- FEMA GRAS: 3166
- Molecular Weight: 218.33 g/mol
- LogP (XLogP): 3.90
- IFRA: SPECIFICATION
Ingredient Data Sheet
CAS 4674-50-4Physical Properties
| Molecular Weight | 218.33 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 3.9🔬 PubChem |
| Boiling Point | 125 °C🔬 EPA CompTox |
| Flash Point | 37.8 °C🔬 EPA CompTox |
| log Kp (skin permeability) | -1.263💻 Calculated |
| SMILES | CC1CC(=O)C=C2C1(CC(CC2)C(=C)C)C🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
Odor & Flavor
| Primary Descriptors | grapefruit• leffingwell |
| Functional Groups | ketonealkene💻 RDKit |
| “The title material has an extremely powerful fruity, sweet and citrusy odor of good tenacity. The odor and flavor are very typical of Grapefruit peel oil in which the material may be present at the rate of about 0.3%.”📖 Arctander | |
| Nootkatone has a pleasant taste.📖 Fenaroli | |
Flavor Notes (Arctander)
| “The title material has an extremely powerful fruity, sweet and citrusy odor of good tenacity. The odor and flavor are very typical of Grapefruit peel oil in which the material may be present at the rate of about 0.3%. Nootkatone has a pleasant taste in concentrations lower than 50 ppm, and although ”📖 Arctander |
Sensory Thresholds
| Odor Detection Threshold | 1.5104 ppm (n=5)📖 van Gemert |
Regulatory Status
| IFRA Listed | Yes — see IFRA Standards for category limits⚖️ IFRA 51 |
| GRAS Status | Generally Recognized as Safe⚖️ FEMA GRAS |
| IOFI Classification | Nature Identical📖 Fenaroli |
Physical data: PubChem (NIH/NLM), U.S. EPA CompTox Dashboard, EPA OPERA models, RDKit. Odor & flavor: Arctander (Perfume & Flavor Chemicals), Fenaroli's Handbook of Flavor Ingredients, Leffingwell. Thresholds: van Gemert (Compilations of Odour Threshold Values). Regulatory: IFRA Standards 51st, FEMA GRAS. Trade names: Surburg (Common Fragrance & Flavor Materials). All data compiled and cross-referenced for perfumertools.com.
Physicochemical Properties
DTXSID: DTXSID8047050
Physical Properties
| Molecular Weight | 218.34 g/mol🔬 EPA CompTox |
| Density | 1.007 g/cm^3🔬 EPA CTX |
| Boiling Point | 302.689 °C📊 OPERA |
| Melting Point | 37.515 °C🔬 EPA CTX |
| Flash Point | 100 °C🔬 EPA CTX |
| Refractive Index | 1.503 Dimensionless📊 OPERA |
| Molar Volume | 225.495 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 3.84 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 3.955 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 3.955 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 7.44 Log10 unitless📊 OPERA |
| Water Solubility | 0.001 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.001 mmHg📊 OPERA |
| Surface Tension | 33.455 dyn/cm📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 17.07 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 1 count💻 Computed |
| Rotatable Bonds | 1 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 66.712 cm^3/mol📊 OPERA |
| Polarizability | 26.447 Å^3📊 OPERA |
Data Sources:
🔬 EPA Experimental data from U.S. EPA CompTox Chemicals Dashboard & CTX APIs. 📊 OPERA Predicted using EPA's OPERA QSAR models. 💻 Computed Calculated from SMILES using RDKit.
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