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Nootkatone
Nootkatone
Nootkatone
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Nootkatone
Nootkatone crystals
Nootkatone crystals
Names
IUPAC name
4α,5α-Eremophila-1(10),11-dien-2-one
Systematic IUPAC name
(4R,4aS,6R)-4,4a-Dimethyl-6-(prop-1-en-2-yl)-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one
Other names
(+)-nootkatone
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.022.840 Edit this at Wikidata
KEGG
UNII
  • InChI=1S/C15H22O/c1-10(2)12-5-6-13-8-14(16)7-11(3)15(13,4)9-12/h8,11-12H,1,5-7,9H2,2-4H3/t11-,12-,15+/m1/s1 checkY
    Key: WTOYNNBCKUYIKC-JMSVASOKSA-N checkY
  • InChI=1/C15H22O/c1-10(2)12-5-6-13-8-14(16)7-11(3)15(13,4)9-12/h8,11-12H,1,5-7,9H2,2-4H3/t11-,12-,15+/m1/s1
    Key: WTOYNNBCKUYIKC-JMSVASOKBQ
  • O=C2\C=C1\CC[C@@H](C(=C)C)C[C@@]1(C)[C@H](C)C2
Properties
C15H22O
Molar mass 218.340 g·mol−1
Appearance Clear or white crystals, impure samples appear as a viscous yellow liquid
Density 0.968 g/mL
Melting point 36 °C (97 °F; 309 K)
Boiling point 170 °C (338 °F; 443 K)
Insoluble in water, very soluble in ethanol, dichloromethane, ethyl acetate, soluble in hexanes
Hazards
GHS labelling:[1]
GHS07: Exclamation mark
Warning
H317
P280
Flash point ~ 100 °C (212 °F; 373 K)
Related compounds
Related terpenes
 Valencene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Nootkatone is an organic compound, a sesquiterpenoid, which means that it is a C15 derivative that also contains an oxygen-containing functional group (a ketone). It is the most valuable aroma compound of grapefruit.[2] Nootkatone was originally isolated from the wood of the Alaskan yellow cedar, Cupressus nootkatensis. The species name, nootkatensis, is derived from the language of the Nuu-Chah-Nulth people of Canada (formerly referred to as the Nootka people).[3]

Production

[edit]

Nootkatone is produced commercially from valencene, another more abundant sesquiterpene.[4]

The conversion of valencene to nootkatone is an example of allylic oxidation.

Allylix (Now Lallemand of Montreal, PQ), developed a fermentation process to nootkatone.[5][6]

Mechanism of action

[edit]

As is true of other plant terpenoids, nootkatone activates α-adrenergic type 1 octopamine receptor (PaOA1) in susceptible arthropods, causing fatal spasms.[7]

Uses

[edit]

Nootkatone in spray form is an effective repellent or insecticide against deer ticks[8][9][10] and lone star ticks.[9][10] It is also an effective repellent or insecticide against mosquitos, and may repel bed bugs, head lice, Formosan termites,[11] and other insects.[12] It is an environmentally friendly insecticide because it is a volatile essential oil that does not persist in the environment.[12] It was approved by the U.S. EPA for this use on August 10, 2020.[13] Its ability to repel ticks, mosquitoes, and other insects may last for hours, in contrast to other plant-based oil repellants like citronella, peppermint oil, and lemongrass oil.[14] It is nontoxic to humans, is an approved food additive,[12] and is commonly used in foods, cosmetics, and pharmaceuticals.[8] The CDC has licensed patents to two companies to produce an insecticide and an insect repellant.[12]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Nootkatone

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from Grokipedia
Nootkatone is a bicyclic with the molecular formula C₁₅H₂₂O, characterized by its distinctive grapefruit-like aroma and role as a key flavor compound in essential oils. It occurs naturally in sources such as grapefruit peel oil, Alaska yellow cedar (Chamaecyparis nootkatensis), vetiver oil, and other fruits like pummelo, where it contributes to the sensory profile of these as a plant metabolite. Chemically, it exists primarily as the (+)-, which exhibits higher bioactivity compared to the (-)-form, and features a carbobicyclic structure with enone functionality. Physically, nootkatone appears as a white crystalline solid with a of 35.5°C, low water solubility (66.87 mg/L at 21°C), and a log Pₒₓ value of 4.05, indicating suitable for fragrance and repellent applications. Beyond its sensory attributes, nootkatone demonstrates versatile biological activities, including , , antiallergic, , and neuroprotective effects, earning it (GRAS) status from the FDA for use as a synthetic agent. In , it functions as an effective and toxicant against pests such as mosquitoes, ticks, bed bugs, , and nematodes, with low (EPA Category IV) and no observed in safety assessments. Its insecticidal properties stem from repulsion and interference with pest behavior, making it a promising biochemical for residential and commercial use, and has been registered by the EPA as a since 2020. Nootkatone's commercial production involves extraction from natural sources like byproducts or microbial via oxidation of the precursor valencene using engineered yeasts or enzymes such as , enabling scalable supply for diverse industries. In the and beverage sector, it is authorized as a flavor additive at levels up to 0.5 mg/kg in , enhancing notes in products like soft drinks and . The and fragrance industry utilizes its pleasant threshold (0.8 ppm in water) for perfumes and personal care items, while emerging research explores its potential in pharmaceuticals for treating conditions like and certain cancers through pathways involving and inhibition. Overall, nootkatone's multifaceted profile underscores its value as a sustainable, multifunctional compound bridging chemistry and applied sciences.

Discovery and History

Isolation and Naming

Nootkatone was first isolated in 1962 from the heartwood essential oil of the Alaskan yellow cedar (Chamaecyparis nootkatensis, also classified as Callitropsis nootkatensis) by chemists Holger Erdtman and Yoshiteru Hirose at the Royal Institute of Technology in Stockholm. The isolation involved steam distillation of the wood to obtain a neutral fraction, followed by chromatographic separation and crystallization, yielding a compound with a distinctive woody, grapefruit-like aroma characteristic of the cedar. This sesquiterpenoid was recognized as the primary contributor to the tree's unique scent profile. The name "nootkatone" originates from the scientific epithet nootkatensis of the source tree, which honors the (historically referred to as the Nootka) Indigenous people whose traditional territories on , , include the type locality of the species near , combined with the chemical suffix "-one" to denote its ketone group. The tree itself was named in 1824 by David Don, reflecting its discovery in that region during early European explorations. In the early , Erdtman and Hirose proposed the of nootkatone as a bicyclic conjugated based on spectroscopic analysis and chemical degradation studies. This elucidation was corroborated in subsequent research, establishing it as an eremophilane-type sesquiterpenoid. It was later identified in grapefruit peel oil in 1964, where it contributes to the fruit's signature aroma.

Commercial Development

Nootkatone garnered early commercial interest in the and within the citrus industry, where it was valued for enhancing grapefruit aroma and flavor profiles in beverages and food products. By 1970, it had been recognized as generally safe (GRAS) by the Flavor and Extract Manufacturers' Association (FEMA), facilitating its adoption as a key ingredient in synthetic formulations despite initial supply limitations from sources like grapefruit peel. In the , advancements in addressed production challenges, with Allylix pioneering a yeast process to biosynthetically produce nootkatone from sugar, enabling scalable and cost-effective supply independent of plant extraction. This method, which converts valencene intermediates to nootkatone, reached commercial-scale production by 2011, reducing costs from over $2,000 per kg and broadening its viability for flavor and fragrance applications. Allylix's innovations were acquired by Evolva in 2014, further integrating the technology into global markets. During the 2010s, the U.S. Centers for Disease Control and Prevention (CDC) advanced nootkatone's potential beyond flavors by patenting its insecticidal properties and licensing the technology to Evolva in for development as a . This collaboration, supported by a 2017 Biomedical Advanced Research and Development Authority (BARDA) contract, culminated in the Agency (EPA) registering nootkatone as a new for insecticides and repellents on August 10, 2020, marking a pivotal milestone for its applications. Post-registration market growth accelerated, with expansion into commercial products by 2021 as companies leveraged the scalable processes. EvoNext Holdings SA (formerly Evolva) introduced NootkaShield, a high-purity (≥99%) nature-identical nootkatone formulation, for integration into and repellents, providing samples to developers and driving adoption in vector-borne disease prevention. In July 2025, Evolva Holding SA changed its name to EvoNext Holdings SA. This shift contributed to the global nootkatone market's estimated size of USD 16.5 million in 2024, projected to reach USD 46.9 million by 2033.

Chemical Properties

Molecular Structure

Nootkatone is classified as a , a C15 derivative, with the molecular formula C15_{15}H22_{22}O and a prominent that contributes to its chemical identity. This structure places it within the eremophilane series of bicyclic sesquiterpene . The systematic IUPAC name for the naturally predominant is (4R,4aS,6R)-4,4a,5,6,7,8-hexahydro-4,4a-dimethyl-6-(prop-1-en-2-yl)-2(3H)-naphthalenone, reflecting its specific at chiral centers C4, C4a, and C6. The core features a bicyclic ring system of two fused six-membered rings (a partially saturated framework), including a cyclohexenone moiety with an α,β-unsaturated in one ring, methyl groups at the ring fusion (positions 4 and 4a), and an isopropenyl at position 6 bearing an exocyclic (=CH2_2). The (+)-nootkatone , with (4R,4aS,6R) configuration, is the primary form found in natural sources. In standard skeletal formula depictions, the structure illustrates the trans-fused bicyclic rings with the conjugated enone system (carbonyl at C2 and between C1-C9a), the angular methyl substituents, and the extending from C6 as -C(CH3_3)=CH2_2, emphasizing the spatial arrangement key to its .

Physical and Chemical Characteristics

Nootkatone appears as white to off-white in its pure form, while impure samples may present as a pale viscous liquid. The compound has a of 218.34 g/mol, a of 36°C, a of 170°C at 10 mmHg, a of 0.968 g/mL, and a of approximately 1.51. Nootkatone exhibits low in , with an experimental value of 66.87 mg/L at 21°C; computational estimates range from 2.4 to 18.5 mg/L, rendering it practically insoluble; it is, however, soluble in organic solvents such as , , , and hexanes. The octanol-water partition coefficient (log Pow_{ow}) is 4.05, indicating high lipophilicity. As a volatile sesquiterpenoid, nootkatone is prone to oxidation in air, with vapor-phase degradation by ozone estimated at a half-life of 12 hours; it is also UV-sensitive due to chromophores absorbing above 290 nm, leading to photolysis. The natural form of nootkatone is optically active, exhibiting a positive specific rotation, typically around [+182°] (c=1 in ethanol) for the dextrorotatory enantiomer derived from grapefruit sources. Its group contributes to reactivity, particularly toward oxidation.

Natural Occurrence and

Sources in

Nootkatone is primarily sourced from the heartwood of the Alaskan yellow cedar (Cupressus nootkatensis, also known as or Chamaecyparis nootkatensis), where it serves as a major component contributing to the tree's characteristic aroma and protective properties. This coniferous species is native to the coastal forests of the , including regions of , , Washington, and , and nootkatone in its heartwood helps confer effects against wood-decaying fungi and . Concentrations in the essential oil can reach up to several percent, varying with factors such as tree age and extraction conditions. Another key natural source is the peel oil of grapefruit (Citrus paradisi), where nootkatone comprises 0.1-0.5% of the oil and acts as the principal compound responsible for the fruit's distinctive aroma. It is biosynthesized from the precursor valencene in tissues. Levels tend to be higher in aged or distilled grapefruit oils due to oxidative processes that enhance formation. Nootkatone is also present in vetiver oil (Vetiveria zizanioides) and in pummelo ( maxima), contributing to their sensory profiles. Trace amounts of nootkatone occur in other species, including lemons (Citrus limon), oranges (), and bergamot (Citrus bergamia), typically at concentrations below 0.05% in their peel oils. In these , nootkatone's bitter plays a role in deterring herbivores, enhancing ecological defense mechanisms.

Biosynthetic Pathway

Nootkatone biosynthesis in plants originates from the universal terpenoid precursor farnesyl pyrophosphate (FPP), a C15 isoprenoid intermediate produced via the mevalonate pathway in the cytosol. The initial committed step involves the cyclization of FPP by sesquiterpene synthases to form valencene, a key hydrocarbon precursor. In Citrus species such as grapefruit (Citrus paradisi), this reaction is catalyzed by valencene synthase, encoded by genes like CsTPS1 (or its orthologs, such as CpVS in grapefruit), which ionizes FPP to a farnesyl cation, followed by electrophilic cyclization through a germacrene A-like intermediate to yield (+)-valencene as the primary product, with minor side products including δ-selinene. Subsequent oxidation of valencene to nootkatone proceeds through allylic to form nootkatol, followed by further oxidation to the . This multi-step oxidation is mediated by monooxygenases (P450s), which introduce oxygen functionality at the allylic position of valencene. While the exact P450(s) in have not been fully characterized in planta, in Alaska cedar the CYP706M1 catalyzes the oxidation of valencene to nootkatone; these enzymes require NADPH and molecular oxygen for activity. studies confirm their role in mimicking the natural pathway. Genes encoding these biosynthetic enzymes exhibit tissue-specific expression, predominantly in the oil glands of fruit peels where terpenoids accumulate. For instance, CsTPS1 transcripts are highly enriched in the flavedo (outer peel layer) of developing fruits, with expression peaking during maturation and regulated by transcription factors like CitAP2.10, correlating with valencene accumulation up to several percent of peel oil content. Cloned from Citrus species, these genes have enabled functional validation through recombinant expression in and , confirming their specificity for FPP and developmental regulation.

Production Methods

Extraction from Natural Sources

Nootkatone is primarily extracted from natural sources through established techniques applied to materials where it occurs in relatively low concentrations, such as the heartwood of certain cedar species and the peel of grapefruit. These methods focus on isolating the compound from essential oils without chemical modification, relying on physical separation processes to obtain crude oils that are further refined. The low natural abundance of nootkatone, stemming from its biosynthetic pathways in , necessitates efficient extraction to make commercial isolation viable. Steam distillation serves as the primary method for extracting nootkatone from cedarwood, particularly from the heartwood chips or sawdust of the Alaska yellow cedar (Chamaecyparis nootkatensis), also known as Nootka cypress. In this process, steam is passed through the finely divided wood material at temperatures of 100-150°C for 6-24 hours, volatilizing the components, which are then condensed and separated. This yields 2-5% by weight, with nootkatone comprising a major fraction—often up to 20-30% of the oil—alongside other sesquiterpenes like valencene and nootkatin. For grapefruit (Citrus paradisi), cold pressing is the standard technique, mechanically rupturing the peel glands to release the oil without heat, which preserves volatile compounds. The resulting cold-pressed peel oil contains 0.2-0.5% nootkatone on average, though concentrations can reach up to 1% in high-quality varieties; this is followed by fractional distillation under reduced pressure to concentrate and purify the nootkatone fraction by separating it from dominant components like limonene. These extraction methods face significant challenges due to the inherently low concentrations of nootkatone in source materials—for instance, approximately 0.005% in the flavedo (outer peel layer) of grapefruit—leading to high costs for large-scale production, as approximately 125,000 kilograms (125 metric tons) of grapefruit are required per kilogram of pure compound. Additionally, seasonal variability in crops affects nootkatone levels, with content fluctuating based on fruit maturity, , and timing, which complicates consistent yields. Historically, cedarwood essential oils were extracted in the early for use in perfumes, providing early sources of nootkatone-like aromas, though the compound itself was not isolated until 1962 from Alaska cedar heartwood; purity enhancements through emerged in the 1970s and advanced with techniques like in the 1980s, enabling higher-grade isolates for flavor and fragrance applications.

Synthetic and Biotechnological Production

Nootkatone can be produced synthetically through the allylic oxidation of valencene, a more abundant derived from oils. Early methods employed in the presence of or tert-butyl , achieving moderate yields but often resulting in impurities due to over-oxidation products. More advanced catalytic approaches, such as manganese-porphyrin complexes with molecular oxygen or cobalt-silver catalysts on silica with tert-butyl , have improved selectivity and yields to 48-87%, though challenges with heavy metal residues and environmental concerns persist. Biotechnological production leverages in microorganisms, particularly , to biosynthesize nootkatone de novo from simple sugars like glucose. Engineered yeast strains express valencene synthase (e.g., CnVS from Cinnamomum camphora) alongside cytochrome P450 monooxygenases (e.g., CnVO) and their reductase partners to convert into valencene and subsequently nootkatone. This approach, pioneered by Allylix (acquired by Lallemand in 2011), enables in bioreactors yielding >90% pure nootkatone at gram-to-kilogram scales, with patents filed throughout the 2010s covering strain optimizations and process scalability. These methods offer significant advantages over natural extraction, including cost-effectiveness by minimizing dependence on variable harvests and enabling consistent, year-round production without seasonal limitations. Scalable fermentations reduce environmental impact compared to chemical routes involving hazardous reagents. Recent advances in the , such as of P450 enzymes and fed-batch optimizations, have boosted titers to over 1 g/L in S. cerevisiae, enhancing commercial viability.

Biological Activities

Insecticidal and Repellent Mechanism

Nootkatone exerts its insecticidal and repellent effects through positive allosteric modulation of the insect (GABA)-gated , known as Rdl (resistant to ), a key component of the in arthropods. At higher concentrations, it acts as an , inhibiting chloride influx and disrupting inhibitory , leading to hyperexcitation of the . This action results in overstimulation of neurons, muscle spasms, , and death in susceptible insects and arachnids, mimicking known GABA antagonists like at toxic doses. The repellent mechanism involves disruption of olfactory and function at lower exposure levels, independent of specific ionotropic receptors like IRs or TRPA1. It interferes with synaptic transmission in , causing spatial aversion in mosquitoes through enhanced activation of Orco-mediated pathways and contact repellency via proboscis-mediated avoidance behaviors. This olfactory disruption prevents host-seeking and landing, providing a non-lethal barrier against pests such as and ticks. Nootkatone demonstrates high selectivity for arthropods due to structural and functional differences between insect Rdl channels and mammalian GABA receptors, resulting in low to vertebrates. Studies show minimal inhibition of mammalian currents at concentrations effective against , explaining its profile for human use. Effective concentrations for repellency range from 1-5%, achieving significant aversion in bioassays, while insecticidal activity requires 10-20% formulations to induce knockdown and mortality. The compound's volatility enables spatial repellency, with protection lasting 4-8 hours on or in field and laboratory tests against mosquitoes and ticks.

Pharmacological Effects

Nootkatone has been shown to stimulate the (AMPK) pathway, a key regulator of cellular , leading to enhanced energy expenditure and fat oxidation in mammalian cells. studies using myocytes demonstrate that nootkatone increases the AMP/ATP ratio, phosphorylates AMPKα, and upregulates peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), promoting and metabolic efficiency. This activation occurs independently of and involves upstream kinases such as LKB1 and Ca²⁺/calmodulin-dependent protein kinase kinase-β. Animal studies highlight nootkatone's potential as an anti-obesity agent through AMPK-mediated mechanisms. In C57BL/6J mice fed a high-fat, high-sucrose diet supplemented with 0.1% to 0.3% nootkatone, long-term administration significantly reduced body weight gain, visceral fat accumulation, , , and hyperleptinemia compared to controls. These effects were accompanied by increased AMPK activity in liver and tissues, resulting in elevated oxygen consumption and improved physical , with mice showing a 21% increase in swimming time to exhaustion. Beyond metabolic effects, nootkatone exhibits anti-inflammatory properties primarily through inhibition of the nuclear factor-kappa B () signaling pathway. In models of particle-induced injury and in mice, nootkatone reduced pro-inflammatory production (e.g., TNF-α, IL-6) by suppressing nuclear translocation and downstream activation. Recent 2025 confirms these effects in (LPS)-induced injury models. It also demonstrates activity in hepatic cells, protecting against in carbon tetrachloride-induced models by enhancing Nrf2/HO-1 pathway expression and reducing levels. Preliminary suggests anticancer potential, particularly in grapefruit-derived nootkatone, which inhibits proliferation in and cells via AMPK activation and arrest at G2/M phase. A 2025 study further shows inhibition of progression via the ATF4-CHOP-CHAC1 pathway. Despite promising preclinical data, nootkatone's translation to human applications is limited by its low oral , attributed to poor and rapid . It holds potential as a for metabolic and inflammatory conditions, but as of November 2025, no human clinical trials have evaluated its pharmacological effects.

Applications

Flavor and Fragrance Uses

Nootkatone possesses a powerful sensory profile characterized by a dominant grapefruit aroma with citrusy, , and slightly spicy undertones, complemented by woody and fruity facets that contribute to its versatility in sensory applications. Its detection threshold is approximately 800 ppb (0.8 ppm) in air, making it highly potent even at trace levels, while thresholds range from 1 ppm in to 6 ppm in . In the flavor industry, nootkatone is widely employed to enhance and notes in beverages, candies, and other foods, typically at concentrations of 1-10 ppm to impart authentic bitterness and depth without overpowering the base profile. It also adds a bitter, woody dimension to non- compositions, such as those evoking , broadening its utility beyond traditional applications. This compound, naturally derived from grapefruit, has been integrated into flavor formulations since the , with synthetic variants favored for their cost-effectiveness and consistent purity. For fragrance applications, nootkatone serves as a key in perfumes, providing fresh, green, and grapefruit accords that elevate citrusy and woody compositions. It is commonly used in colognes and soaps at levels of 0.1-1% to boost and ensure longevity, particularly in men's fragrances where its dry, character adds structure and vibrancy. Nootkatone holds (GRAS) status from the U.S. for use as a synthetic substance in products, affirming its for sensory enhancement in consumer goods.

Pest Control Applications

Nootkatone has demonstrated efficacy as an and repellent against several key pests, including the deer tick (), lone star tick (), Aedes species mosquitoes, bed bugs (), head lice (Pediculus humanus capitis), and Formosan subterranean termites (Coptotermes formosanus). These applications leverage its natural origin from grapefruit and cedar, allowing for targeted deterrence in both personal and environmental settings. Common formulations include topical repellents such as sprays and lotions at concentrations of 5-20%, spatial insecticides for area treatment, and treated fabrics like or nets. These provide protection for up to several hours against mosquitoes and ticks, often outperforming essential oil-based alternatives like citronella due to greater stability. For instance, 20% nootkatone formulations have shown repellency comparable to 7% against and in laboratory arm-in-cage tests. Field studies have reported high , with nootkatone achieving over 90% repellency against at optimal concentrations in natural settings. NootkaShield, an EPA-registered introduced in 2020 (with product development ongoing as of 2025), is intended for incorporation into commercial repellents for and on and , building on CDC demonstrating sustained in outdoor trials. As of November 2025, nootkatone-based consumer repellent products remain in development, though market reports project growth in the segment, with the global nootkatone market valued at approximately USD 11-33 million in 2025, driven by demand for natural alternatives. Compared to , nootkatone offers advantages including a pleasant scent, non-greasy texture, and biodegradability as a naturally derived compound. Its low toxicity profile, recognized as generally safe (GRAS) by the FDA for use, makes it suitable for children and pregnant individuals without the skin irritation concerns associated with synthetic alternatives.

Safety and Regulation

Toxicity and Safety Profile

Nootkatone exhibits low acute toxicity across multiple exposure routes. In oral administration studies, the median lethal dose (LD50) in rats exceeds 5,000 mg/kg body weight, classifying it as practically non-toxic under standard toxicity categories. Dermal and inhalation LD50 values are similarly high, with no observed adverse effects at tested doses up to these limits. Regarding irritation, nootkatone shows no significant eye irritation at concentrations up to 100%, rated as Toxicity Category IV, and only mild skin irritation potential, also Category IV, without causing corrosion or severe reactions. Chronic exposure assessments indicate no genotoxic effects, as evidenced by negative results in bacterial reverse mutation assays and micronucleus tests. Carcinogenicity has not been observed in available studies, with no structural alerts or data triggering further Tier II/III evaluations by regulatory bodies. For dermal applications, nootkatone is considered safe at concentrations up to 20% , with a (NOAEL) of 75 mg/kg/day in repeated-dose studies, though higher doses may cause minor irritation. Allergenicity concerns are minimal, with human repeated insult patch tests showing no sensitization reactions at typical use levels exceeding 98% purity. Nootkatone has been affirmed as (GRAS) by the for use as a agent in since its evaluation in the 1970s comprehensive GRAS review process. In terms of environmental fate relevant to safety profiles, nootkatone undergoes rapid volatilization, with an atmospheric half-life of approximately 2.6 hours due to reactions with hydroxyl radicals and . Biodegradation occurs quickly in and , with laboratory half-lives around 1.3 days under aerobic conditions, supporting low persistence. Bioaccumulation potential is limited, evidenced by an (log Kow) of 3.84 and a bioconcentration factor (BCF) of 159 in , below thresholds for significant accumulation.

Regulatory Status and Environmental Impact

Nootkatone has been affirmed as safe for use as a synthetic substance and adjuvant in by the U.S. (FDA), as listed in 21 CFR 172.515. This affirmation supports its (GRAS) status for flavor and fragrance applications in products. In the United States, the Environmental Protection Agency (EPA) registered nootkatone on August 10, 2020, as a biochemical pesticide active ingredient under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). This registration enables its use in developing insect repellents and insecticides. Additionally, low-concentration products containing nootkatone qualify for exemption from full FIFRA registration as minimum risk pesticides under EPA's 25(b) program. On November 17, 2025, the EPA established an exemption from the requirement for a tolerance for residues of nootkatone when used as an inert ingredient (up to 100 ppm end-use concentration) in pesticide formulations applied to food-contact surfaces, further supporting its low-risk profile. Internationally, nootkatone is approved as a substance in the under Regulation (EC) No 1334/2008, with the designation FL-no: 07.089. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) evaluated nootkatone in 2004 and identified no safety concerns at estimated dietary exposure levels, supporting its inclusion on safe lists for food use, which extends to low-risk applications like repellents. Environmentally, nootkatone offers benefits as a non-persistent biochemical that degrades rapidly in the environment, minimizing long-term ecological residues compared to synthetic alternatives. Its use reduces reliance on conventional synthetic pesticides, promoting safer (IPM) strategies for controlling vectors of diseases such as (via ticks) and (via mosquitoes). This aligns with broader efforts to lower environmental impacts while effectively managing pests.

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