Estragole

Estragole at a Glance

Estragole, or methylchavicol (1-allyl-4-methoxybenzene), is an allylbenzene phenylpropanoid — the volatile that dominates the essential oils of tarragon, Mexican tarragon (Tagetes lucida) and the estragole chemotypes of sweet basil, and a significant fraction of fennel and anise oils.

Unlike most molecules here, its defining literature is toxicological, not therapeutic. Estragole is a genotoxic rodent hepatocarcinogen: it is bioactivated in the liver to a DNA-reactive metabolite, it induced liver tumours in mice and rats, and the EU Committee on Herbal Medicinal Products (HMPC) treats it as a genotoxic carcinogen with no established safe threshold ^{1,2,15Reference 1Miller EC et al. · 1983AnimalStructure-activity studies of the carcinogenicities in the mouse and rat of some naturally occurring and synthetic alkenylbenzene derivatives related to safrole and estragoleView study →Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →Reference 15European Medicines AgencyPublic statement on the use of herbal medicinal products containing estragoleView study →}. Read it as a safety brief on a flavour compound, not a monograph on a remedy.

It does have genuine but secondary bioactivities — modest antibacterial (including antibiotic synergy), mild antispasmodic and insecticidal effects — all preclinical and all capped by the carcinogenicity. Keep estragole distinct from eugenol (a clove phenol not in this genotoxic class) and group it with its true relatives methyl-eugenol and safrole.

What It's Used For

Estragole’s real activities are minor and entirely preclinical. They matter only as context — none is large enough to weigh against the carcinogenicity, and any ingested or systemic use is ruled out by it.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume. A beta, not a validated metric. These are the secondary bioactivities; the dominant, best-evidenced property is carcinogenicity, covered under Toxicity & Safety. All scores stay low by design.

01Antibacterial / antibiotic synergyShaky30%Isolate MICs + meropenem/tobramycin synergy vs MDR-XDR Gram-negatives ^{12,13Reference 12Araque M et al. · 2026Antibacterial activity of estragole from Ocimum tenuiflorum and Tagetes lucida and synergistic effect with meropenem and tobramycin against multidrug- and extensively drug-resistant (MDR-XDR) Gram-negative bacteriaView study →Reference 13Andrade TCB et al. · 2015Isolation, characterization and evaluation of antimicrobial and cytotoxic activity of estragole, obtained from the essential oil of Croton zehntneri (Euphorbiaceae)View study →}

02Antispasmodic (smooth muscle)Shaky28%Croton-oil constituent studies on tracheal & intestinal muscle ^{14Reference 14Lima CC et al. · 2020Antispasmodic effects of the essential oil of Croton zehntneri, anethole, and estragole, on tracheal smooth muscleView study →}

03Insecticidal / larvicidalShaky22%Essential-oil constituent bioassays ^{13Reference 13Andrade TCB et al. · 2015Isolation, characterization and evaluation of antimicrobial and cytotoxic activity of estragole, obtained from the essential oil of Croton zehntneri (Euphorbiaceae)View study →}

Pharmacokinetics

Estragole is lipophilic and readily absorbed, then partitioned between detoxication and bioactivation in a dose-dependent way — the single most important PK fact for its safety. In rats and mice, low doses are handled mainly by O-demethylation and side-chain cleavage (detoxication); as dose rises, O-demethylation falls and 1’-hydroxylation rises, feeding the carcinogenic pathway ^{3Reference 3Anthony A et al. · 1987AnimalMetabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1’-hydroxyestragoleView study →}. The proximate carcinogen 1’-hydroxyestragole is then sulfonated by SULT1A1 to the unstable 1’-sulfooxy ester, which collapses to the DNA-reactive carbenium ion ^{2,6Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →Reference 6Suzuki Y et al. · 2012AnimalPossible involvement of sulfotransferase 1A1 in estragole-induced DNA modification and carcinogenesis in the livers of female miceView study →}; sulfotransferase inhibition (e.g. pentachlorophenol) sharply reduces adduct binding and tumour formation, confirming the SULT step as decisive ^{2Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →}. Physiologically-based biokinetic (PBBK) modelling comparing humans with rats found 1’-sulfooxyestragole formation only modestly higher in human liver and predicted minor species differences at dietary exposure levels, because a competing oxidation of 1’-hydroxyestragole to 1’-oxoestragole is the main human detox route ^{4Reference 4Punt A et al. · 2009AnimalUse of physiologically based biokinetic (PBBK) modeling to study estragole bioactivation and detoxification in humans as compared with male ratsView study →}. Net: the toxicokinetics — not receptor affinity — govern estragole’s risk, and they are non-linear with dose.

Clinical Trials

There are no human clinical trials of estragole — nor would there be, for a genotoxic carcinogen. The human-relevant evidence is toxicological and regulatory (EU SCF opinion; EMA/HMPC public statement) plus PBBK translation of the animal carcinogenicity data ^{4,15,16Reference 4Punt A et al. · 2009AnimalUse of physiologically based biokinetic (PBBK) modeling to study estragole bioactivation and detoxification in humans as compared with male ratsView study →Reference 15European Medicines AgencyPublic statement on the use of herbal medicinal products containing estragoleView study →Reference 16Scientific Committee on Food (SCF) · 2001Opinion of the Scientific Committee on Food on estragole (1-allyl-4-methoxybenzene). https://ec.europa.eu/food/fs/sc/scf/out104_en.pdfView study →}. The secondary antibacterial/antispasmodic/insecticidal findings are all preclinical.

Last checked: July 2026.

The Genotoxic Bioactivation Pathway

Estragole is not itself the carcinogen — it is a procarcinogen that the liver converts, in two enzymatic steps, into a DNA-reactive electrophile. This cascade is the replicated, mechanism-defining finding and the reason the regulatory posture is precautionary: the endpoint is direct DNA damage, with no demonstrable threshold.

The sequence runs:

1. CYP-mediated 1’-hydroxylation. Hepatic cytochrome P450 (CYP1A2-led) oxidises estragole at the 1’ position to the proximate carcinogen 1’-hydroxyestragole. This is the rate-setting activation step and the one that rises disproportionately as dose increases ^{3Reference 3Anthony A et al. · 1987AnimalMetabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1’-hydroxyestragoleView study →}.
2. SULT1A1 sulfonation. Sulfotransferase 1A1 conjugates 1’-hydroxyestragole to 1’-sulfooxyestragole, the unstable ultimate carcinogen — the decisive step, since inhibiting SULT abolishes most adduct formation and tumour induction ^{2,6Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →Reference 6Suzuki Y et al. · 2012AnimalPossible involvement of sulfotransferase 1A1 in estragole-induced DNA modification and carcinogenesis in the livers of female miceView study →}.
3. Carbenium-ion formation → DNA adducts. The sulfooxy ester spontaneously loses sulfate to give a reactive carbenium ion, which attacks DNA to form N²-deoxyguanosine and N⁶-deoxyadenosine adducts — demonstrable in primary rat hepatocytes and CYP1A2-competent human liver cells ^{2,6,7Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →Reference 6Suzuki Y et al. · 2012AnimalPossible involvement of sulfotransferase 1A1 in estragole-induced DNA modification and carcinogenesis in the livers of female miceView study →Reference 7Schulte-Hubbert R et al. · 2020AnimalEstragole: DNA adduct formation in primary rat hepatocytes and genotoxic potential in HepG2-CYP1A2 cellsView study →}.

Competing detoxication routes (O-demethylation, side-chain cleavage, glucuronidation, and oxidation of 1’-hydroxyestragole to 1’-oxoestragole) divert estragole away from this pathway and dominate at low dose — the basis of the dose-dependence of risk ^{3,4Reference 3Anthony A et al. · 1987AnimalMetabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1’-hydroxyestragoleView study →Reference 4Punt A et al. · 2009AnimalUse of physiologically based biokinetic (PBBK) modeling to study estragole bioactivation and detoxification in humans as compared with male ratsView study →}.

This CYP → SULT → carbenium-ion cascade is the shared signature of estragole, methyl-eugenol and safrole. Eugenol lacks the 1’-allylic activation and is not in this class — see below.

Toxicity & Safety

This is the section that defines the molecule. Estragole is a genotoxic rodent hepatocarcinogen, and the regulatory posture is precautionary because the activating pathway is a DNA-reactive one with no demonstrable threshold.

Genotoxic Carcinogenicity — The Anchoring Data

Estragole carries a carcinogen flag on the strength of classic structure–activity carcinogenicity studies: dietary estragole and its metabolite 1’-hydroxyestragole induced hepatocellular tumours in mice and rats, with hepatomas in 56–71% of high-dose CD-1 mice fed 0.23–0.46% estragole in the diet for twelve months ^{1Reference 1Miller EC et al. · 1983AnimalStructure-activity studies of the carcinogenicities in the mouse and rat of some naturally occurring and synthetic alkenylbenzene derivatives related to safrole and estragoleView study →}. The mechanism is genotoxic — the CYP1A2 → SULT1A1 → carbenium-ion cascade forms N²-deoxyguanosine and N⁶-deoxyadenosine DNA adducts ^{2,6,7Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →Reference 6Suzuki Y et al. · 2012AnimalPossible involvement of sulfotransferase 1A1 in estragole-induced DNA modification and carcinogenesis in the livers of female miceView study →Reference 7Schulte-Hubbert R et al. · 2020AnimalEstragole: DNA adduct formation in primary rat hepatocytes and genotoxic potential in HepG2-CYP1A2 cellsView study →}. Sulfotransferase inhibition abolishes most adduct binding and tumour formation, pinpointing the SULT step ^{2Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →}; adduct formation is demonstrable in primary rat hepatocytes and CYP1A2-competent human liver cells ^{7Reference 7Schulte-Hubbert R et al. · 2020AnimalEstragole: DNA adduct formation in primary rat hepatocytes and genotoxic potential in HepG2-CYP1A2 cellsView study →}. Sex differences track Sult1a1 expression, with higher adduct loads in female mice ^{6Reference 6Suzuki Y et al. · 2012AnimalPossible involvement of sulfotransferase 1A1 in estragole-induced DNA modification and carcinogenesis in the livers of female miceView study →}.

Developmental & Genotoxic Reach

As a genotoxic carcinogen acting through a reactive electrophile, estragole carries transplacental and germ-relevant concern — a DNA-reactive metabolite is, by nature, not confined to the somatic liver. On this basis, medicinal-strength or essential-oil-level exposure should be avoided in pregnancy. This is a finding stated for the molecule, not a per-herb verdict: pregnancy and lactation decisions belong to the herb or product page where intake is actually decided.

Dose & Matrix — Real Caveats, Bounded

Toxicokinetics are non-linear: at low doses detoxication dominates and bioactivation is minor ^{3Reference 3Anthony A et al. · 1987AnimalMetabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1’-hydroxyestragoleView study →}, PBBK modelling predicts only modest human-vs-rat differences at dietary levels ^{4Reference 4Punt A et al. · 2009AnimalUse of physiologically based biokinetic (PBBK) modeling to study estragole bioactivation and detoxification in humans as compared with male ratsView study →}, and co-occurring herb flavonoids (notably nevadensin) and whole decoctions can suppress adduct formation ^{5,9Reference 5Alhusainy W et al. · 2012AnimalMatrix modulation of the bioactivation of estragole by constituents of different alkenylbenzene-containing herbs and spices and physiologically based biokinetic modeling of possible in vivo effectsView study →Reference 9Gori L et al. · 2012Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety updateView study →}. These arguments lower estimated real-world risk from ordinary culinary use — they do not license medicinal dosing, essential-oil ingestion, or use of estragole as an added flavouring. The prudent reading, matching the regulators: minimise exposure, avoid concentrated oils and isolates, and avoid medicinal/essential-oil-level intake in pregnancy.

Safety at a Glance

☣️ Carcinogen

• Genotoxic carcinogen. Dietary estragole caused liver tumours in mice and rats; it is bioactivated to a DNA-adduct-forming metabolite ^{1,2,7Reference 1Miller EC et al. · 1983AnimalStructure-activity studies of the carcinogenicities in the mouse and rat of some naturally occurring and synthetic alkenylbenzene derivatives related to safrole and estragoleView study →Reference 2Fennell TR et al. · 1985AnimalMajor role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male miceView study →Reference 7Schulte-Hubbert R et al. · 2020AnimalEstragole: DNA adduct formation in primary rat hepatocytes and genotoxic potential in HepG2-CYP1A2 cellsView study →}.
• No safe threshold set. The EU HMPC declines to define an exact limit and advises exposure be kept as low as practically achievable ^{15,16Reference 15European Medicines AgencyPublic statement on the use of herbal medicinal products containing estragoleView study →Reference 16Scientific Committee on Food (SCF) · 2001Opinion of the Scientific Committee on Food on estragole (1-allyl-4-methoxybenzene). https://ec.europa.eu/food/fs/sc/scf/out104_en.pdfView study →}.
• Concentrated oils/isolates are the real exposure. Essential oils, distillates and estragole-rich chemotype oils — not trace culinary garnish — drive risk ^{9,11Reference 9Gori L et al. · 2012Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety updateView study →Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}.
• Developmental/genotoxic reach. As a genotoxic carcinogen acting through a reactive electrophile, it carries transplacental/germ-relevant concern; avoid medicinal or essential-oil-level exposure in pregnancy (finding stated, not a per-herb verdict).
• Dose- and matrix-dependent, not risk-free. Low-dose detoxication and whole-herb flavonoids blunt but do not remove the hazard ^{3,5,9Reference 3Anthony A et al. · 1987AnimalMetabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1’-hydroxyestragoleView study →Reference 5Alhusainy W et al. · 2012AnimalMatrix modulation of the bioactivation of estragole by constituents of different alkenylbenzene-containing herbs and spices and physiologically based biokinetic modeling of possible in vivo effectsView study →Reference 9Gori L et al. · 2012Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety updateView study →}.
• Trace dietary use is low-concern. Ordinary culinary amounts of the fresh herbs deliver very little estragole; the debate is about medicinal doses, oils and isolates ^{9,11Reference 9Gori L et al. · 2012Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety updateView study →Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}.

Regulatory Status

The EU Scientific Committee on Food (SCF) and the EMA Committee on Herbal Medicinal Products (HMPC) classify estragole as a naturally occurring genotoxic carcinogen of DNA potency comparable to safrole. Given the background dietary exposure and the mechanistic uncertainty of a DNA-reactive endpoint, the HMPC does not set an exact safe limit and instead requires that intake from herbal medicinal products be kept as low as practically achievable, with guidance/safety values periodically revised downward ^{15,16Reference 15European Medicines AgencyPublic statement on the use of herbal medicinal products containing estragoleView study →Reference 16Scientific Committee on Food (SCF) · 2001Opinion of the Scientific Committee on Food on estragole (1-allyl-4-methoxybenzene). https://ec.europa.eu/food/fs/sc/scf/out104_en.pdfView study →}.

There is no IARC classification for estragole. Its close relative methyl-eugenol has been evaluated by IARC as Group 2A (probably carcinogenic to humans), but estragole itself has not received an IARC monograph classification — so none is assigned it an IARC group. The operative regulatory framing for estragole remains the EU SCF/HMPC “no safe threshold” position, not an IARC category.

The Whole-Herb vs. Isolate Risk Debate

Nearly all of the carcinogenicity evidence is the isolated molecule given at high dietary doses to rodents (e.g. 0.23–0.46% estragole in the diet of CD-1 mice for twelve months, producing hepatomas in 56–71% of animals) ^{1Reference 1Miller EC et al. · 1983AnimalStructure-activity studies of the carcinogenicities in the mouse and rat of some naturally occurring and synthetic alkenylbenzene derivatives related to safrole and estragoleView study →} — deliberately far above culinary human intake. The open question is whether that isolate hazard transfers to whole-herb exposure, and here the matrix genuinely matters.

Alhusainy and colleagues showed that flavonoids from estragole-containing herbs (notably nevadensin) inhibit the SULT step and shift metabolism toward glucuronidation, lowering predicted DNA-adduct formation ^{5Reference 5Alhusainy W et al. · 2012AnimalMatrix modulation of the bioactivation of estragole by constituents of different alkenylbenzene-containing herbs and spices and physiologically based biokinetic modeling of possible in vivo effectsView study →}; Gori et al. argued pure estragole is partly inactivated within a fennel-seed decoction ^{9Reference 9Gori L et al. · 2012Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety updateView study →}; and one fennel-isolate comet assay in HepG2 cells was even negative under its conditions ^{8Reference 8Villarini M et al. · 2014Investigation of the cytotoxic, genotoxic, and apoptosis-inducing effects of estragole isolated from fennel (Foeniculum vulgare)View study →}. Water extracts of tarragon carry very little estragole and are treated as low-risk ^{11Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}.

The consensus reading: the whole-plant matrix modulates — it can meaningfully blunt — the hazard, but it does not abolish it, and concentrated essential oils, distillates and isolated estragole are the exposures of concern ^{5,9,11Reference 5Alhusainy W et al. · 2012AnimalMatrix modulation of the bioactivation of estragole by constituents of different alkenylbenzene-containing herbs and spices and physiologically based biokinetic modeling of possible in vivo effectsView study →Reference 9Gori L et al. · 2012Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety updateView study →Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}. Regulators price this uncertainty in rather than out.

Estragole vs. Eugenol & the Allylbenzenes

Estragole sits inside a small family of plant allylalkoxybenzenes whose members differ sharply in hazard, and the difference is chemical, not incidental:

• The 1’-hydroxylation carcinogens — estragole, methyl-eugenol and safrole — all carry an unsubstituted allyl side chain that CYP can hydroxylate at the 1’ position, feeding the SULT → carbenium-ion → DNA-adduct pathway above. They share the same genotoxic-carcinogen signature.
• Eugenol is not in that class. Its free phenolic hydroxyl is directly conjugated (glucuronidated/sulfated) and excreted, so eugenol is not bioactivated through 1’-sulfoöxylation the way estragole is; its safety profile is a different, dose-dependent-hepatotoxicity story, not a genotoxic-carcinogen one. Conflating the two is the single most common error about estragole.
• Anethole, the propenyl isomer of estragole found alongside it in these same oils, has its double bond conjugated into the ring rather than terminal, and is metabolised and regulated as a separate case.

The practical upshot: a molecule’s membership in this family is decided by whether it has the 1’-activatable allyl chain. Estragole has it; eugenol does not.

Prevalence in Nature

Estragole is a phenylpropanoid built from the phenylalanine/cinnamate pathway, occurring chiefly in the essential oils of the Apiaceae (fennel, anise), Asteraceae (Tagetes, Artemisia), Lamiaceae (sweet basil) and Euphorbiaceae (Croton). It is frequently the dominant oil constituent: Tagetes lucida aerial-part oil can be 95–97% methylchavicol — one of the purest natural sources known ^{10Reference 10Cicció JF · 2004A source of almost pure methyl chavicol: volatile oil from the aerial parts of Tagetes lucida (Asteraceae) cultivated in Costa RicaView study →}; French/culinary tarragon (Artemisia dracunculus) oil runs up to ~82% in high-estragole chemotypes ^{11Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}; sweet-basil “estragole chemotypes” are estragole-rich; and fennel (Foeniculum vulgare) seed oil carries ~2–29%, higher in bitter var. vulgare ^{9,11Reference 9Gori L et al. · 2012Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety updateView study →Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}.

Chemotype and provenance are the master variables — Russian tarragon and geraniol/geranyl-acetate Tagetes chemotypes contain far less estragole than their culinary/high-estragole counterparts ^{10,11Reference 10Cicció JF · 2004A source of almost pure methyl chavicol: volatile oil from the aerial parts of Tagetes lucida (Asteraceae) cultivated in Costa RicaView study →Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}. Its close structural cousins in these same oils — methyl-eugenol, anethole and safrole — track alongside it and are governed by the same chemotype splits.

Discovery & Synthesis

Estragole takes its name from estragon, the French word for tarragon, the herb from which the aroma principle was characterised; the synonym methylchavicol reflects its relationship to chavicol (4-allylphenol) as the 4-methyl ether. As a simple, abundant allylanisole it was identified among the classic essential-oil volatiles of the nineteenth/early-twentieth-century flavour chemistry era; a precise “first isolation” attribution is not well documented in the primary literature.

Structurally it is 1-allyl-4-methoxybenzene, and it can be prepared synthetically (e.g. by O-methylation/allylation routes around the anisole nucleus). It is an isomer of anethole (the propenyl isomer), into and out of which it can interconvert under isomerising conditions. Commercially, estragole is obtained by fractionation of estragole-rich essential oils (tarragon, basil, Tagetes) and as a flavour/fragrance intermediate; because of the carcinogenicity findings its deliberate use as an added flavouring is restricted rather than expanded.

Patents: not yet researched.

Dosage

There is no recommended dose — estragole is a genotoxic carcinogen for which no safe threshold has been established, so the meaningful figure is an exposure limit, not an intake target. The numbers in the literature are either toxicology study doses (e.g. 0.23–0.46% dietary estragole in the rodent carcinogenicity work ^{1Reference 1Miller EC et al. · 1983AnimalStructure-activity studies of the carcinogenicities in the mouse and rat of some naturally occurring and synthetic alkenylbenzene derivatives related to safrole and estragoleView study →}, or the wide 0.05–1000 mg/kg metabolism range ^{3Reference 3Anthony A et al. · 1987AnimalMetabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1’-hydroxyestragoleView study →}) or regulatory guidance values aimed at capping intake from herbal medicinal products ^{15Reference 15European Medicines AgencyPublic statement on the use of herbal medicinal products containing estragoleView study →}.

The operative guidance is the EU HMPC’s: keep estragole exposure as low as practically achievable, prefer water-based preparations of the source herbs over essential oils or distillates (water extracts carry far less estragole ^{11Reference 11Obolskiy D et al. · 2011ReviewArtemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safetyView study →}), and avoid medicinal-strength or essential-oil-level exposure — especially in pregnancy. These are exposure-limitation figures, not a personal recommendation to consume estragole.

References

1. Miller EC, et al. (1983). Structure-activity studies of the carcinogenicities in the mouse and rat of some naturally occurring and synthetic alkenylbenzene derivatives related to safrole and estragole. Cancer Research. https://pubmed.ncbi.nlm.nih.gov/6825084/
2. Fennell TR, et al. (1985). Major role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1’-hydroxy-2’,3’-dehydroestragole in infant male mice. Cancer Research. https://pubmed.ncbi.nlm.nih.gov/3863702/
3. Anthony A, et al. (1987). Metabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1’-hydroxyestragole. Food and Chemical Toxicology. https://pubmed.ncbi.nlm.nih.gov/3121480/
4. Punt A, et al. (2009). Use of physiologically based biokinetic (PBBK) modeling to study estragole bioactivation and detoxification in humans as compared with male rats. Toxicological Sciences. https://pubmed.ncbi.nlm.nih.gov/19447879/
5. Alhusainy W, et al. (2012). Matrix modulation of the bioactivation of estragole by constituents of different alkenylbenzene-containing herbs and spices and physiologically based biokinetic modeling of possible in vivo effects. Toxicological Sciences. https://pubmed.ncbi.nlm.nih.gov/22649189/
6. Suzuki Y, et al. (2012). Possible involvement of sulfotransferase 1A1 in estragole-induced DNA modification and carcinogenesis in the livers of female mice. Mutation Research. https://pubmed.ncbi.nlm.nih.gov/22885592/
7. Schulte-Hubbert R, et al. (2020). Estragole: DNA adduct formation in primary rat hepatocytes and genotoxic potential in HepG2-CYP1A2 cells. Toxicology. https://pubmed.ncbi.nlm.nih.gov/32853702/
8. Villarini M, et al. (2014). Investigation of the cytotoxic, genotoxic, and apoptosis-inducing effects of estragole isolated from fennel (Foeniculum vulgare). Journal of Natural Products. https://pubmed.ncbi.nlm.nih.gov/24617303/
9. Gori L, et al. (2012). Can estragole in fennel seed decoctions really be considered a danger for human health? A fennel safety update. Evidence-Based Complementary and Alternative Medicine. https://pubmed.ncbi.nlm.nih.gov/22899959/
10. Cicció JF. (2004). A source of almost pure methyl chavicol: volatile oil from the aerial parts of Tagetes lucida (Asteraceae) cultivated in Costa Rica. Revista de Biología Tropical. https://pubmed.ncbi.nlm.nih.gov/17354394/
11. Obolskiy D, et al. (2011). Artemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safety. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/21942448/
12. Araque M, et al. (2026). Antibacterial activity of estragole from Ocimum tenuiflorum and Tagetes lucida and synergistic effect with meropenem and tobramycin against multidrug- and extensively drug-resistant (MDR-XDR) Gram-negative bacteria. MicrobiologyOpen. https://pubmed.ncbi.nlm.nih.gov/41725358/
13. Andrade TCB, et al. (2015). Isolation, characterization and evaluation of antimicrobial and cytotoxic activity of estragole, obtained from the essential oil of Croton zehntneri (Euphorbiaceae). Anais da Academia Brasileira de Ciências. https://pubmed.ncbi.nlm.nih.gov/25789792/
14. Lima CC, et al. (2020). Antispasmodic effects of the essential oil of Croton zehntneri, anethole, and estragole, on tracheal smooth muscle. Heliyon. https://pubmed.ncbi.nlm.nih.gov/33251351/
15. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Public statement on the use of herbal medicinal products containing estragole. https://www.ema.europa.eu/en/use-herbal-medicinal-products-containing-estragole-scientific-guideline
16. Scientific Committee on Food (SCF), European Commission (2001). Opinion of the Scientific Committee on Food on estragole (1-allyl-4-methoxybenzene). https://ec.europa.eu/food/fs/sc/scf/out104_en.pdf

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