Imperatorin

Imperatorin at a Glance

Imperatorin is a linear furanocoumarin from angelica and bishop’s weed, and a member of the compound class responsible for both phototoxicity and the grapefruit–drug interaction.

Its preclinical activity is unusually broad for a coumarin: anti-inflammatory and analgesic through NF-kB and MAPK, sodium-channel anticonvulsant and GABAergic anxiolytic effects, and vasodilation.

Its furanocoumarin structure is also the source of its main caution — photosensitisation and CYP-mediated interaction potential.

One Molecule, Four Names

Imperatorin, marmelosin, ammidin and pentosalen are the same compound, and the literature does not always know it. Papers on bael (Aegle marmelos) fruit almost always call it marmelosin — so the antioxidant and TNF-α-suppressing work on “marmelosin” ^{18Reference 18Pynam H · 2018In vitroAntioxidant and anti-inflammatory properties of marmelosin from Bael (Aegle marmelos L.); Inhibition of TNF-α mediated inflammatory/tumor markers — in vitroView study →} and the imperatorin work on Angelica belong to one molecule, not two. Anyone reading across those literatures without collapsing the names will double-count the evidence and miss the exposure: a person eating bael fruit and a person taking an angelica root preparation are taking the same furanocoumarin.

Two things follow. The safety profile below applies to all four names — including the fruit literature, where phototoxicity is rarely mentioned. And the isolate evidence is broader than the imperatorin literature alone suggests.

Imperatorin vs. the Other Furanocoumarins

Every plant that makes imperatorin makes several furanocoumarins, and their properties are not interchangeable. Angelica dahurica root alone yields nine of them — imperatorin, isoimperatorin, oxypeucedanin, oxypeucedanin hydrate, bergapten, xanthotoxin, xanthotoxol, isopimpinellin and psoralen ^{13Reference 13Chen L et al. · 2015AnimalSeparation and simultaneous quantification of nine furanocoumarins from Radix Angelicae dahuricae using liquid chromatography with tandem mass spectrometry for bioavailability determination in rats — rat pharmacokinetic animal modelView study →}. Getting a claim onto the right molecule is most of the work on a page like this.

Phototoxicity is a graded property, not a class label. Thirteen furanocoumarins were run through photo-cytotoxicity, photo-mutagenicity and photo-clastogenicity assays in V79 cells, and the potencies differ widely between them — enough that a relative-potency-factor system, with 5-methoxypsoralen (bergapten) set at 1.00, was needed to describe them and proved additive across mixtures ^{16Reference 16Raquet N · 2014In vitroApplication of the equivalency factor concept to the phototoxicity and -genotoxicity of furocoumarin mixtures — in vitroView study →}. That same work modelled a mixture built on the furanocoumarin pattern of an Angelica archangelica extract ^{16Reference 16Raquet N · 2014In vitroApplication of the equivalency factor concept to the phototoxicity and -genotoxicity of furocoumarin mixtures — in vitroView study →}. Imperatorin is one of the congeners tested, and a weaker photosensitiser than bergapten or 8-methoxypsoralen. Weaker is not zero: as a psoralen-family molecule it still absorbs UVA and forms DNA photoadducts, and it is the reason the caution on this molecule is real rather than theoretical.

The CYP story is where mis-attribution is most common. “Furanocoumarins cause the grapefruit interaction” is a class sentence covering molecule-specific facts. The grapefruit-type, mechanism-based inactivation of intestinal CYP3A4 is best characterised for bergamottin, a citrus-peel furanocoumarin, and has been modelled quantitatively as such ^{26Reference 26Fuhr LM et al. · 2023Physiologically Based Pharmacokinetic Modeling of Bergamottin and 6,7-Dihydroxybergamottin to Describe CYP3A4 Mediated Grapefruit-Drug InteractionsView study →}. Imperatorin’s own documented interaction is different and narrower: it is a mechanism-based inactivator of CYP2B6 ^{15Reference 15Zheng L et al. · 2015In vitroImperatorin is a mechanism-based inactivator of CYP2B6 — in vitroView study →} and altered macitentan disposition through CYP3A4 in vitro and in vivo ^{14Reference 14Wu H et al. · 2025In vitroDrug Interactions of Imperatorin and Curcumin on Macitentan in vitro and in vivoView study →}. Both are real. Neither is the grapefruit effect, and imperatorin should not be described as if it were bergamottin. The neighbouring simple coumarin osthole, which is not a furanocoumarin at all, has neither property.

What It's Used For

Imperatorin is a linear furanocoumarin — structurally in the psoralen family alongside bergapten and 8-MOP — concentrated in the roots and seeds of angelica (Angelica archangelica, A. dahurica, not A. sinensis/Dong Quai) and bishop’s weed (Ammi majus). Its preclinical activity is broad: anti-inflammatory/analgesic via NF-κB and MAPK suppression ^{6,7Reference 6Singh G et al. · 2020AnimalAnti-nociceptive and anti-inflammatory effect of imperatorin: evidences for involvement of COX-2, iNOS, NFκB and inflammatory cytokines — animal modelView study →Reference 7Ge JW et al. · 2022AnimalImperatorin inhibits mitogen-activated protein kinase and nuclear factor kappa-B signaling pathways and alleviates neuroinflammation in ischemic stroke — animal modelView study →}, sodium-channel anticonvulsant and GABAergic anxiolytic effects ^{1,2Reference 1Luszczki JJ et al. · 2007AnimalTime-course and dose-response relationships of imperatorin in the mouse maximal electroshock seizure threshold modelView study →Reference 2Wu KC et al. · 2013In vitroSuppression of voltage-gated Na(+) channels and neuronal excitability by imperatorin — in vitroView study →}, and NO/calcium-mediated vasodilation ^{10,11Reference 10Nie H et al. · 2009AnimalImperatorin is responsible for the vasodilatation activity of Angelica dahurica var. formosana regulated by nitric oxide in an endothelium-dependent manner — rat in vivo animal modelView study →Reference 11Zhang Y et al. · 2010AnimalRole of store-operated calcium entry in imperatorin-induced vasodilatation of rat small mesenteric artery — animal modelView study →}.

Two things frame it, and both are furanocoumarin-class properties that dominate the safety story: it is a UV photosensitizer and a CYP3A4/2C/2B6 inhibitor with grapefruit-type drug-interaction potential ^{16,14Reference 16Raquet N · 2014In vitroApplication of the equivalency factor concept to the phototoxicity and -genotoxicity of furocoumarin mixtures — in vitroView study →Reference 14Wu H et al. · 2025In vitroDrug Interactions of Imperatorin and Curcumin on Macitentan in vitro and in vivoView study →}.

It is poorly bioavailable, and there are no human trials of the isolate.

Evidence by IndicationStrength of support · Beta

01Anti-inflammatory / analgesicShaky42%Multiple in-vivo rodent models on NF-κB/MAPK ^{6,7,8,9Reference 6Singh G et al. · 2020AnimalAnti-nociceptive and anti-inflammatory effect of imperatorin: evidences for involvement of COX-2, iNOS, NFκB and inflammatory cytokines — animal modelView study →Reference 7Ge JW et al. · 2022AnimalImperatorin inhibits mitogen-activated protein kinase and nuclear factor kappa-B signaling pathways and alleviates neuroinflammation in ischemic stroke — animal modelView study →Reference 8Park G et al. · 2026AnimalGlehnia littoralis and imperatorin attenuate allergic airway inflammation via mast cell stabilization and transcriptome-defined suppression of FcεRI/TLR-MAPK/NF-κB signaling — mouse model with human primary immune cellsView study →Reference 9Liu M et al. · 2018AnimalActivating the pregnane X receptor by imperatorin attenuates dextran sulphate sodium-induced colitis in mice — mouse modelView study →}

02Neuroprotective / anticonvulsantShaky40%Most-replicated, but partly contradicted ^{1,2,3,5Reference 1Luszczki JJ et al. · 2007AnimalTime-course and dose-response relationships of imperatorin in the mouse maximal electroshock seizure threshold modelView study →Reference 2Wu KC et al. · 2013In vitroSuppression of voltage-gated Na(+) channels and neuronal excitability by imperatorin — in vitroView study →Reference 3Budzynska B et al. · 2012AnimalThe effects of imperatorin on anxiety and memory-related behavior in male Swiss mice — mouse modelView study →Reference 5Suciu F et al. · 2025AnimalInvestigation of Anticonvulsant Potential of Morus alba, Angelica archangelica, Valeriana officinalis, and Passiflora incarnata Extracts: In Vivo and In Silico StudiesView study →}

03VasodilatoryShaky30%Consistent rat vascular data, two mechanisms ^{10,11Reference 10Nie H et al. · 2009AnimalImperatorin is responsible for the vasodilatation activity of Angelica dahurica var. formosana regulated by nitric oxide in an endothelium-dependent manner — rat in vivo animal modelView study →Reference 11Zhang Y et al. · 2010AnimalRole of store-operated calcium entry in imperatorin-induced vasodilatation of rat small mesenteric artery — animal modelView study →}

04AnticancerShaky22%In-vitro cytotoxicity, formulation-dependent ^{12Reference 12Grabarska A et al. · 2020In vitroImperatorin as a Promising Chemotherapeutic Agent Against Human Larynx Cancer and Rhabdomyosarcoma Cells — in vitroView study →}

05Antibacterial / anti-virulenceShaky20%Single mechanism study on Shigella SOD ^{19Reference 19Raja SB et al. · 2011In vitroImperatorin a furocoumarin inhibits periplasmic Cu-Zn SOD of Shigella dysenteriae thereby modulating its resistance towards phagocytosis during host pathogen interaction — in vitroView study →}

Mechanisms

Pharmacokinetics

Imperatorin is highly lipophilic and poorly water-soluble, and much of the applied literature reaches for enabling formulations — lipid microspheres, self-emulsifying systems — to raise exposure. It is extensively metabolised by hepatic CYPs, which is the same enzyme relationship that produces its interaction risk.

“Poorly bioavailable” is repeated more often than it is measured. The one study that put numbers on it dosed rats with a Radix Angelicae dahuricae extract and quantified all nine of its furanocoumarins in plasma; oral bioavailability across the nine spanned 10.1% to 82.8% ^{13Reference 13Chen L et al. · 2015AnimalSeparation and simultaneous quantification of nine furanocoumarins from Radix Angelicae dahuricae using liquid chromatography with tandem mass spectrometry for bioavailability determination in rats — rat pharmacokinetic animal modelView study →}. That is a wide range, and it means the class-level assumption of poor absorption does not settle the question for imperatorin specifically.

Before absorption, some of it stops being imperatorin. Incubated with human faecal microbiota — and with Blautia sp. MRG-PMF1 in isolation — imperatorin is deprenylated to xanthotoxol, the first reported cleavage of a prenyl aryl ether by gut bacteria ^{22Reference 22Tan SRS et al. · 2020In vitroGut Metabolism of Furanocoumarins: Proposed Function of Co O-Methyltransferase — in vitroView study →}. Isoimperatorin goes the same way, to bergaptol. This matters more than a typical metabolism note: an oral dose of imperatorin partly becomes a different furanocoumarin in the gut, one with its own photochemistry, before anything is absorbed. Any in-vitro result obtained by putting imperatorin directly on cells has skipped that step.

Clinical Trials

There are no human trials of isolated imperatorin, and it is not sold as an isolated supplement. The nearest human-relevant data are ex vivo: TNF-α and IL-6 suppression in house-dust-mite-stimulated human PBMCs ^{8Reference 8Park G et al. · 2026AnimalGlehnia littoralis and imperatorin attenuate allergic airway inflammation via mast cell stabilization and transcriptome-defined suppression of FcεRI/TLR-MAPK/NF-κB signaling — mouse model with human primary immune cellsView study →}. Everything else is animal, cell or whole-preparation — and the 2025 whole-extract anticonvulsant study was animal and in-silico, with a non-significant result for Angelica ^{5Reference 5Suciu F et al. · 2025AnimalInvestigation of Anticonvulsant Potential of Morus alba, Angelica archangelica, Valeriana officinalis, and Passiflora incarnata Extracts: In Vivo and In Silico StudiesView study →}.

Last checked: September 2026.

Isolate vs. Plant Studies

The isolate/plant gap is unusually sharp for imperatorin, and it points in the uncomfortable direction.

The isolate looks good. Purified imperatorin raises the maximal-electroshock seizure threshold dose-dependently ^{1Reference 1Luszczki JJ et al. · 2007AnimalTime-course and dose-response relationships of imperatorin in the mouse maximal electroshock seizure threshold modelView study →}, suppresses voltage-gated Na⁺ channels in neurons ^{2Reference 2Wu KC et al. · 2013In vitroSuppression of voltage-gated Na(+) channels and neuronal excitability by imperatorin — in vitroView study →}, and in a head-to-head mouse comparison reached ED50 167–290 mg/kg against valproate’s 189–255 mg/kg, with a protective index of 1.13–2.60 against valproate’s 1.72–2.00 — the same experiment that ran osthole, which was about half as potent ^{25Reference 25Luszczki JJ et al. · 2009AnimalAnticonvulsant and acute neurotoxic effects of imperatorin, osthole and valproate in the maximal electroshock seizure and chimney tests in mice: a comparative studyView study →}.

The plant does not. A 2025 study of whole Angelica archangelica extract in vivo found only non-significant anticonvulsant activity ^{5Reference 5Suciu F et al. · 2025AnimalInvestigation of Anticonvulsant Potential of Morus alba, Angelica archangelica, Valeriana officinalis, and Passiflora incarnata Extracts: In Vivo and In Silico StudiesView study →}. The isolate’s potency does not transfer to the crude herb — the single most important honesty note here. Whether that is a content problem (too little imperatorin in the extract), an absorption problem, or interference from the other constituents is not resolved.

Where the two agree, they agree properly. In the Glehnia littoralis work the extract and the isolated molecule were tested in the same experiment, imperatorin was identified as the primary bioactive constituent, and both reduced cytokines in human PBMCs — the correct way to attribute a plant’s effect to a molecule ^{8Reference 8Park G et al. · 2026AnimalGlehnia littoralis and imperatorin attenuate allergic airway inflammation via mast cell stabilization and transcriptome-defined suppression of FcεRI/TLR-MAPK/NF-κB signaling — mouse model with human primary immune cellsView study →}. The bael-fruit results are the opposite arrangement: the antioxidant and TNF-α work is on isolated marmelosin ^{18Reference 18Pynam H · 2018In vitroAntioxidant and anti-inflammatory properties of marmelosin from Bael (Aegle marmelos L.); Inhibition of TNF-α mediated inflammatory/tumor markers — in vitroView study →}, but the HepG2 chromium-protection study used a marmelosin-rich extract, not the pure compound ^{21Reference 21Katram N et al. · 2021In vitroAegle marmelos extract rich in marmelosin exerted ameliorative effect against chromium-induced oxidative stress and apoptosis through regulation of Gadd45 in HepG2 cell line — in vitroView study →}, and cannot be read as a molecule result.

Its Role in Plants

Furanocoumarins are a chemical defence with a light switch. Imperatorin and its relatives are built from the phenylpropanoid pathway via umbelliferone, prenylated and then cyclised to the fused furan ring that defines the class; imperatorin carries the prenyl group as an ether at C-8. That ring is what makes the molecule photoactive: absorbing UVA, it forms covalent adducts with DNA. In a plant being eaten in daylight, that is a defence that costs the plant nothing to arm and costs the herbivore its genome.

It works on more than insects. The imperatorin-containing furanocoumarin fraction of northern prickly ash is antifungal, and its activity is light-dependent — the same photochemistry, aimed at a different attacker ^{20Reference 20Bafi-Yeboa NF et al. · 2005In vitroAntifungal constituents of northern prickly ash, Zanthoxylum americanum Mill. — in vitroView study →}. Against bacteria the mechanism is not photochemical at all: imperatorin disables Shigella’s superoxide dismutase ^{19Reference 19Raja SB et al. · 2011In vitroImperatorin a furocoumarin inhibits periplasmic Cu-Zn SOD of Shigella dysenteriae thereby modulating its resistance towards phagocytosis during host pathogen interaction — in vitroView study →}.

The families that invest in this chemistry are the ones that keep appearing on the list below: Apiaceae and Rutaceae, with scattered occurrences elsewhere. In both, the furanocoumarins concentrate in the organs worth defending — seeds, fruits and roots — rather than in leaves.

Prevalence in Nature

Imperatorin is a furanocoumarin of the Apiaceae and Rutaceae, and it is never alone. It occurs alongside bergapten, xanthotoxin, isopimpinellin, psoralen, isoimperatorin and oxypeucedanin in proportions that vary with species, chemotype and plant part ^{13,16Reference 13Chen L et al. · 2015AnimalSeparation and simultaneous quantification of nine furanocoumarins from Radix Angelicae dahuricae using liquid chromatography with tandem mass spectrometry for bioavailability determination in rats — rat pharmacokinetic animal modelView study →Reference 16Raquet N · 2014In vitroApplication of the equivalency factor concept to the phototoxicity and -genotoxicity of furocoumarin mixtures — in vitroView study →}.

Its richest documented sources are the roots and seeds of angelica — Angelica archangelica and A. dahurica (bai zhi), not A. sinensis (dong quai) — and bishop’s weed (Ammi majus), where it sits with xanthotoxin, bergapten and several relatives ^{13,17Reference 13Chen L et al. · 2015AnimalSeparation and simultaneous quantification of nine furanocoumarins from Radix Angelicae dahuricae using liquid chromatography with tandem mass spectrometry for bioavailability determination in rats — rat pharmacokinetic animal modelView study →Reference 17Knapp CF 3rd · 2009ReviewBotanical briefs: garden Angelica (Angelica archangelica) — reviewView study →}. It is also recorded in khella (Ammi visnaga), parsnip (Pastinaca sativa), Glehnia littoralis (bei sha shen), the storksbills (Erodium spp.) and Malachra fasciata. In the Rutaceae it appears in bael fruit (Aegle marmelos), where the literature calls it marmelosin ^{18Reference 18Pynam H · 2018In vitroAntioxidant and anti-inflammatory properties of marmelosin from Bael (Aegle marmelos L.); Inhibition of TNF-α mediated inflammatory/tumor markers — in vitroView study →}, and in northern prickly ash (Zanthoxylum americanum), confirmed by HPLC in fruit and leaf ^{20Reference 20Bafi-Yeboa NF et al. · 2005In vitroAntifungal constituents of northern prickly ash, Zanthoxylum americanum Mill. — in vitroView study →}. Bergamot and other citrus carry furanocoumarins including imperatorin in the peel oil.

Human exposure is therefore mostly dietary and incidental — parsnip, bael fruit, citrus peel oil — rather than deliberate, with concentrated exposure only from angelica or Ammi preparations.

Major Natural Sources

Source	Family	Part	Notes
Angelica archangelica, A. dahurica	Apiaceae	Root, seed	The reference sources; nine furanocoumarins quantified together in A. dahurica 13Reference 13Chen L et al. · 2015AnimalSeparation and simultaneous quantification of nine furanocoumarins from Radix Angelicae dahuricae using liquid chromatography with tandem mass spectrometry for bioavailability determination in rats — rat pharmacokinetic animal modelView study →
Ammi majus (bishop’s weed)	Apiaceae	Seed	With xanthotoxin, bergapten, alloimperatorin 17Reference 17Knapp CF 3rd · 2009ReviewBotanical briefs: garden Angelica (Angelica archangelica) — reviewView study →
Ammi visnaga (khella)	Apiaceae	Seed	With xanthotoxin and marmesin
Glehnia littoralis (bei sha shen)	Apiaceae	Root	Identified as the extract’s primary bioactive constituent 8Reference 8Park G et al. · 2026AnimalGlehnia littoralis and imperatorin attenuate allergic airway inflammation via mast cell stabilization and transcriptome-defined suppression of FcεRI/TLR-MAPK/NF-κB signaling — mouse model with human primary immune cellsView study →
Pastinaca sativa (parsnip)	Apiaceae	Root	Dietary exposure; with xanthotoxin, bergapten, isopimpinellin
Aegle marmelos (bael)	Rutaceae	Fruit	Reported as marmelosin 18,21Reference 18Pynam H · 2018In vitroAntioxidant and anti-inflammatory properties of marmelosin from Bael (Aegle marmelos L.); Inhibition of TNF-α mediated inflammatory/tumor markers — in vitroView study →Reference 21Katram N et al. · 2021In vitroAegle marmelos extract rich in marmelosin exerted ameliorative effect against chromium-induced oxidative stress and apoptosis through regulation of Gadd45 in HepG2 cell line — in vitroView study →
Zanthoxylum americanum (northern prickly ash)	Rutaceae	Fruit, leaf	HPLC-confirmed in the antifungal fraction 20Reference 20Bafi-Yeboa NF et al. · 2005In vitroAntifungal constituents of northern prickly ash, Zanthoxylum americanum Mill. — in vitroView study →
Citrus bergamia and other citrus	Rutaceae	Peel oil	One furanocoumarin among several

Quantified content figures per source are largely absent from the accessible literature, so this table records occurrence and part rather than concentration.

Discovery & Synthesis

Imperatorin is named for the plant it was taken from — Imperatoria ostruthium, masterwort (now Peucedanum ostruthium) — and it comes out of the same 1930s Viennese chemistry that produced osthole. Butenandt and Marten worked through the masterwort constituents in 1932 as part of a study of plant fish and insect poisons ^{27Reference 27Butenandt A · 1932Untersuchungen über pflanzliche Fisch- und InsektengifteView study →}, and in 1933 Ernst Späth and Hermann Holzen established imperatorin’s constitution as the C-8 prenyl ether of xanthotoxol ^{23Reference 23Späth E · 1933Späth E, Holzen H (1933). Über pflanzliche Fischgifte, V. Mitteil.: Die Konstitution des Imperatorins (aus Imperatoria Ostruthium). Berichte der deutschen chemischen Gesellschaft. https://doi.org/10.1002/cber.19330660823View study →}. The same pair reported a partial synthesis in 1935, along with the preparation of oxy-imperatorin ^{24Reference 24Späth E · 1935Teilsynthese des Imperatorins und Darstellung des Oxy-imperatorins (XVView study →}; Späth’s group went on to synthesise most of the linear furanocoumarins — bergaptol, xanthotoxin, isoimperatorin and oxypeucedanin — over the following six years.

Supply today is extraction. Imperatorin is obtained from Angelica dahurica or Ammi majus material for research use; there is no commercial-scale synthetic route, and no reason for one, since it is not a licensed drug and is not sold as a supplement. The gut-bacterial deprenylation that converts it to xanthotoxol ^{22Reference 22Tan SRS et al. · 2020In vitroGut Metabolism of Furanocoumarins: Proposed Function of Co O-Methyltransferase — in vitroView study →} is, in effect, the reverse of Späth’s 1935 partial synthesis — biology removing the prenyl group chemistry had to install.

Patents: not yet researched.

Toxicity & Safety

Imperatorin has two real hazards and both come from its furanocoumarin chemistry rather than any organ toxicity — it photosensitizes skin to UV, and it inhibits drug-metabolizing enzymes the way grapefruit does.

Safety at a Glance

⚠️ Moderate toxicityPhotosensitivityDrug interactions

• Phototoxic under UVA. As a psoralen-family furanocoumarin it can form DNA photoadducts; contact plus sun exposure causes burning, blistering and lingering pigmentation.
• Grapefruit-type drug interactions. It inhibits CYP3A4/2C and irreversibly inactivates CYP2B6, so it can raise levels of co-administered drugs.
• Avoid in pregnancy and lactation. Photoactive and DNA-reactive with no human safety data.
• Less potent than bergapten or 8-MOP. Relative-potency work across thirteen furanocoumarins shows the class spans a wide range and adds up predictably in mixtures — imperatorin sits below the reference psoralens, but the risk is real at high or topical exposure.
• Gut bacteria change what you absorbed. Some of an oral dose is deprenylated to xanthotoxol before absorption, so the exposure is to two furanocoumarins, not one.

Full Safety & Interactions Detail

Imperatorin’s two real, mechanistically-grounded hazards are both furanocoumarin-class properties. (1) Phototoxicity: as a linear furanocoumarin (psoralen family) it absorbs UVA and can form DNA photoadducts — furanocoumarin mixtures are photo-cytotoxic and photo-genotoxic under UVA ^{16Reference 16Raquet N · 2014In vitroApplication of the equivalency factor concept to the phototoxicity and -genotoxicity of furocoumarin mixtures — in vitroView study →}, and furanocoumarin-rich plant contact plus sun exposure causes phytophotodermatitis (burning, blistering, lingering hyperpigmentation) ^{17Reference 17Knapp CF 3rd · 2009ReviewBotanical briefs: garden Angelica (Angelica archangelica) — reviewView study →}.

Imperatorin is a less potent photosensitizer than bergapten or 8-MOP; the relative-potency-factor system that quantifies this, with 5-methoxypsoralen set at 1.00, was shown to be additive across mixtures, including one modelled on an Angelica archangelica extract ^{16Reference 16Raquet N · 2014In vitroApplication of the equivalency factor concept to the phototoxicity and -genotoxicity of furocoumarin mixtures — in vitroView study →} — so what a person is exposed to from a plant preparation is the sum of its furanocoumarins, not imperatorin alone. The risk is real for topical or high-dose exposure to imperatorin-rich material — advise sun caution. (2) CYP inhibition (drug interactions): this is the same enzyme-inhibition mechanism by which grapefruit furanocoumarins raise drug levels — imperatorin inhibits CYP3A4/CYP2C and altered the disposition of co-administered drugs such as macitentan ^{14Reference 14Wu H et al. · 2025In vitroDrug Interactions of Imperatorin and Curcumin on Macitentan in vitro and in vivoView study →}, and it is a mechanism-based (irreversible) inactivator of CYP2B6 ^{15Reference 15Zheng L et al. · 2015In vitroImperatorin is a mechanism-based inactivator of CYP2B6 — in vitroView study →}.

The grapefruit interaction itself is best characterised for a different furanocoumarin, bergamottin ^{26Reference 26Fuhr LM et al. · 2023Physiologically Based Pharmacokinetic Modeling of Bergamottin and 6,7-Dihydroxybergamottin to Describe CYP3A4 Mediated Grapefruit-Drug InteractionsView study →}; what imperatorin has is its own CYP2B6 and CYP3A4 evidence, which is enough to treat imperatorin-rich preparations as capable of raising the levels of CYP3A4/2C/2B6 substrates. A third route is worth naming: imperatorin activates the pregnane X receptor ^{9Reference 9Liu M et al. · 2018AnimalActivating the pregnane X receptor by imperatorin attenuates dextran sulphate sodium-induced colitis in mice — mouse modelView study →}, the transcriptional switch that induces CYP3A4 — so inhibition and induction are both on the table, and the net effect of chronic exposure has not been studied. Together these two hazards put imperatorin above an ordinary plant coumarin on caution. Its photosensitising potency sits below that of 8-MOP and bergapten — the psoralens used deliberately as photosensitisers in clinical PUVA.

Dosage

There is no established human dose, and imperatorin is not sold as an isolated supplement. The figures below are the exposures used in the research described above.

Human exposure happens incidentally, through Angelica, Ammi, bael or citrus-peel preparations, where imperatorin is one constituent among several furanocoumarins. For those, follow the parent-herb guidance and observe the sun-exposure and drug-interaction cautions above. These are doses studied in research and are not a personal recommendation.

References

1. Luszczki JJ, Glowniak K, Czuczwar SJ (2007). Time-course and dose-response relationships of imperatorin in the mouse maximal electroshock seizure threshold model. Neuroscience Research. https://pubmed.ncbi.nlm.nih.gov/17602770/
2. Wu KC, Chen YH, Cheng KS, et al. (2013). Suppression of voltage-gated Na(+) channels and neuronal excitability by imperatorin — in vitro. European Journal of Pharmacology. https://pubmed.ncbi.nlm.nih.gov/24113522/
3. Budzynska B, Kruk-Slomka M, Skalicka-Wozniak K, et al. (2012). The effects of imperatorin on anxiety and memory-related behavior in male Swiss mice — mouse model. Experimental and Clinical Psychopharmacology. https://pubmed.ncbi.nlm.nih.gov/22686497/
4. Butt AM, Chopra M, Bhagwani A, et al. (2026). Imperatorin, a natural furanocoumarin alleviates chronic neuropathic pain by targeting GABAergic tone in an animal model of spinal cord injury. Natural Product Research. https://pubmed.ncbi.nlm.nih.gov/39676602/
5. Suciu F, Mihai DP, Ungurianu A, et al. (2025). Investigation of Anticonvulsant Potential of Morus alba, Angelica archangelica, Valeriana officinalis, and Passiflora incarnata Extracts: In Vivo and In Silico Studies. International Journal of Molecular Sciences. https://pubmed.ncbi.nlm.nih.gov/40650201/
6. Singh G, Kaur J, Kaur M, et al. (2020). Anti-nociceptive and anti-inflammatory effect of imperatorin: evidences for involvement of COX-2, iNOS, NFκB and inflammatory cytokines — animal model. International Journal of Neuroscience. https://pubmed.ncbi.nlm.nih.gov/31524564/
7. Ge JW, Deng SJ, Xue ZW, et al. (2022). Imperatorin inhibits mitogen-activated protein kinase and nuclear factor kappa-B signaling pathways and alleviates neuroinflammation in ischemic stroke — animal model. CNS Neuroscience & Therapeutics. https://pubmed.ncbi.nlm.nih.gov/34674376/
8. Park G, Kang TK, Le TT, et al. (2026). Glehnia littoralis and imperatorin attenuate allergic airway inflammation via mast cell stabilization and transcriptome-defined suppression of FcεRI/TLR-MAPK/NF-κB signaling — mouse model with human primary immune cells. Journal of Ethnopharmacology. https://pubmed.ncbi.nlm.nih.gov/42264445/
9. Liu M, Zhang G, Zheng C, et al. (2018). Activating the pregnane X receptor by imperatorin attenuates dextran sulphate sodium-induced colitis in mice — mouse model. British Journal of Pharmacology. https://pubmed.ncbi.nlm.nih.gov/29945292/
10. Nie H, Meng LZ, Zhou JY, et al. (2009). Imperatorin is responsible for the vasodilatation activity of Angelica dahurica var. formosana regulated by nitric oxide in an endothelium-dependent manner — rat in vivo animal model. Chinese Journal of Integrative Medicine. https://pubmed.ncbi.nlm.nih.gov/20082250/
11. Zhang Y, Wang QL, Zhan YZ, et al. (2010). Role of store-operated calcium entry in imperatorin-induced vasodilatation of rat small mesenteric artery — animal model. European Journal of Pharmacology. https://pubmed.ncbi.nlm.nih.gov/20813104/
12. Grabarska A, Skalicka-Woźniak K, Kiełbus M, et al. (2020). Imperatorin as a Promising Chemotherapeutic Agent Against Human Larynx Cancer and Rhabdomyosarcoma Cells — in vitro. Molecules. https://pubmed.ncbi.nlm.nih.gov/32353989/
13. Chen L, Jian Y, Wei N, et al. (2015). Separation and simultaneous quantification of nine furanocoumarins from Radix Angelicae dahuricae using liquid chromatography with tandem mass spectrometry for bioavailability determination in rats — rat pharmacokinetic animal model. Journal of Separation Science. https://pubmed.ncbi.nlm.nih.gov/26496866/
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