Acacetin

Acacetin at a Glance

Acacetin is a naturally occurring methylated flavone — structurally it is apigenin with a single methyl group added to the 4’-hydroxyl, making it apigenin 4’-methyl ether (5,7-dihydroxy-4’-methoxyflavone). It occurs in chrysanthemum flowers, black locust, Korean mint, damiana and dream herb, most often bound as its 7-O-glycosides rather than as the free aglycone.

Its most distinctive research signal is cardiac: acacetin is an atrial-selective blocker of the ultrarapid delayed-rectifier potassium current (I_Kur / Kv1.5) and has been developed as a candidate anti-atrial-fibrillation agent, including proof-of-concept work in large animals ^{1,3Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →}. Beyond the heart it shows anti-inflammatory, anticancer, neuroprotective and antidiabetic activity across cell and rodent models ^{13Reference 13Singh S et al. · 2020Acacetin, a flavone with diverse therapeutic potential in cancer, inflammation, infections and other metabolic disordersView study →}.

Two honesty caveats frame the whole page. First, essentially all of the efficacy evidence is animal or in-vitro — there are no human efficacy trials of acacetin. Second, the isolated aglycone has poor oral bioavailability, which is exactly why the cardiac programme had to build a water-soluble prodrug to test it in vivo ^{1,11Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →Reference 11Han DG et al. · 2021AnimalInvestigation of the factors responsible for the poor oral bioavailability of acacetin in rats: physicochemical and biopharmaceutical aspectsView study →}. Toxicity data are limited but point to a low-risk dietary flavone.

Acacetin vs. Apigenin

The single fact that defines this molecule is that it is apigenin carrying one extra methyl group on the 4’-oxygen. That small change — 4’-O-methylation — is worth stating plainly, because it is the reason acacetin has its own page rather than being folded into apigenin.

Methylation of a flavone hydroxyl tends to:

• Increase lipophilicity, changing membrane partitioning and how the molecule interacts with ion channels and transporters.
• Remove one hydrogen-bond donor, which alters both target binding and the pattern of phase-II conjugation (methylated flavones can resist some glucuronidation/sulfation at that position, though acacetin is still heavily conjugated elsewhere).
• Shift the biological emphasis — acacetin’s marquee activity (atrial-selective Kv1.5 block) is more pronounced than for apigenin, whereas apigenin’s best-known signals are its anxiolytic and broad anti-inflammatory profiles.

The two are close chemical relatives with overlapping antioxidant and anti-inflammatory behaviour, but they are not interchangeable, and results for one should not be assumed for the other.

The Atrial-Selective Antiarrhythmic Story

The reason acacetin is studied at all outside general flavone screening is a specific and unusual cardiac property: it preferentially blocks potassium currents that repolarize atrial — not ventricular — heart muscle.

In isolated human atrial myocytes, acacetin inhibits the ultrarapid delayed-rectifier current (I_Kur), carried by the Kv1.5 channel, along with the transient outward current (I_to) and the acetylcholine-activated current (I_KACh) ^{1Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →}. Because I_Kur/Kv1.5 is expressed in human atria but essentially absent from ventricle, blocking it prolongs the atrial effective refractory period without the ventricular repolarization delay that makes many conventional antiarrhythmics pro-arrhythmic. In the landmark study, acacetin prevented experimentally induced atrial fibrillation in anaesthetized dogs ^{1Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →}. Mechanistically, it is an open-channel blocker of hKv1.5 with frequency- and use-dependence — it binds preferentially when the channel is repeatedly opening, i.e. during the rapid atrial rates of fibrillation ^{2Reference 2Wu HJ et al. · 2011Acacetin causes a frequency- and use-dependent blockade of hKv1.5 channels by binding to the S6 domain of the channel poreView study →}.

The translational obstacle was solubility and oral bioavailability. To carry the molecule forward, researchers synthesised a highly water-soluble acacetin prodrug, which suppressed experimental atrial fibrillation in beagle dogs — an explicit engineering answer to the parent compound’s pharmacokinetic weakness ^{3Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →}. This large-animal, prodrug-enabled programme is what separates acacetin from the many flavones with only cell-culture data; it remains, however, preclinical — no human antiarrhythmic trials have been reported.

What It's Used For

Acacetin’s pharmacology spans several organ systems, but the evidence is heavily weighted toward the cardiac ion-channel work; the rest is a broad flavone profile of anti-inflammatory, anticancer, neuroprotective and metabolic effects in cells and rodents.

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. No application here has human efficacy data, so all scores stay modest; the cardiac row ranks highest only because it reaches large-animal in-vivo proof of concept.

01Atrial Antiarrhythmic (I_Kur/Kv1.5)Promising46%Human atrial-myocyte electrophysiology + anti-AF efficacy in dogs (isolate + prodrug) ^{1,2,3Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →Reference 2Wu HJ et al. · 2011Acacetin causes a frequency- and use-dependent blockade of hKv1.5 channels by binding to the S6 domain of the channel poreView study →Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →}

02Anti-InflammatoryShaky34%Isolate ↓ NF-κB/MAPK, E-selectin, LPS-driven mediators in vitro and in mice ^{4,5Reference 4Tanigawa N et al. · 2013Acacetin inhibits expression of E-selectin on endothelial cells through regulation of the MAP kinase signaling pathway and activation of NF-κBView study →Reference 5Ha SK et al. · 2012In vitroAcacetin attenuates neuroinflammation via regulation the response to LPS stimuli in vitro and in vivoView study →}

03AnticancerShaky30%Apoptosis/cell-cycle arrest in oral & head-and-neck carcinoma lines ^{6,7Reference 6Kim CD et al. · 2015The mechanism of acacetin-induced apoptosis on oral squamous cell carcinomaView study →Reference 7Sun F et al. · 2019Acacetin-induced cell apoptosis in head and neck squamous cell carcinoma cells: evidence for the role of a mitochondria-dependent pathwayView study →}

04NeuroprotectiveShaky24%Rodent neuroinflammation / microglial-suppression models ^{5,8Reference 5Ha SK et al. · 2012In vitroAcacetin attenuates neuroinflammation via regulation the response to LPS stimuli in vitro and in vivoView study →Reference 8Liu Y et al. · 2024Acacetin inhibits activation of microglia to improve neuroinflammation after subarachnoid hemorrhageView study →}

05AntidiabeticShaky22%Insulin-independent GLUT4 translocation in myotubes; enzyme inhibition ^{9Reference 9Kwon EB et al. · 2020Acacetin enhances glucose uptake through insulin-independent GLUT4 translocation in L6 myotubesView study →}

06Aromatase InhibitionShaky20%Enzyme assay in damiana constituent screen (IC₅₀ ~18.7 µM) ^{10Reference 10Zhao J et al. · 2008Anti-aromatase activity of the constituents from damiana (Turnera diffusa)View study →}

Mechanisms

The load-bearing mechanism is the atrial-selective potassium-channel block — I_Kur/Kv1.5 is present in human atrium but not ventricle, which is why acacetin can prolong atrial refractoriness without the ventricular effects that make many antiarrhythmics dangerous ^{1,2Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →Reference 2Wu HJ et al. · 2011Acacetin causes a frequency- and use-dependent blockade of hKv1.5 channels by binding to the S6 domain of the channel poreView study →}.

Pharmacokinetics

Acacetin’s pharmacokinetics are the crux of interpreting every in-vitro result above. The free aglycone has poor oral bioavailability: it is poorly water-soluble, undergoes extensive first-pass phase-II metabolism (glucuronidation and sulfation) and is subject to efflux transport, so systemic exposure after oral dosing is low ^{11Reference 11Han DG et al. · 2021AnimalInvestigation of the factors responsible for the poor oral bioavailability of acacetin in rats: physicochemical and biopharmaceutical aspectsView study →}. Detailed rat work attributes this to “triple recycling” processes — enterohepatic and enteric recirculation of its conjugates — that shape both systemic and local bioavailability ^{12Reference 12Dai P et al. · 2015Triple recycling processes impact systemic and local bioavailability of orally administered flavonoids (acacetin)View study →}. The practical consequence is direct: the anti-atrial-fibrillation programme did not dose the parent molecule systemically but instead synthesised a water-soluble prodrug to reach efficacious exposures in dogs ^{3Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →}. Any read-across from a micromolar in-vitro potency to a human systemic effect must be discounted heavily against this bioavailability ceiling. Robust human ADME parameters are not established.

Clinical Trials

There are no human efficacy trials of acacetin for any indication. The strongest evidence is large-animal (canine) proof of concept for atrial fibrillation using the isolate and a prodrug ^{1,3Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →}; everything else is cell-culture or rodent work.

Last checked: July 2026.

Isolate vs. Plant Studies

Acacetin sits firmly on the isolate side of the ledger. The cardiac electrophysiology, the anti-inflammatory signalling work, the cancer cell-line studies and the antidiabetic myotube data all test the purified molecule (or, for the in-vivo AF work, a synthetic prodrug of it) — not a chrysanthemum, black-locust or damiana extract ^{1,3,6,9Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →Reference 6Kim CD et al. · 2015The mechanism of acacetin-induced apoptosis on oral squamous cell carcinomaView study →Reference 9Kwon EB et al. · 2020Acacetin enhances glucose uptake through insulin-independent GLUT4 translocation in L6 myotubesView study →}. That is methodologically clean, but it creates the opposite problem from the usual whole-plant caveat: because acacetin is present in plants mostly as its 7-O-glycosides (such as linarin) and at low, poorly-quantified levels, and because the free aglycone is poorly absorbed, the isolate results do not transfer back to any claim about eating the source herbs. Where acacetin appears in a whole-plant story — for instance as one of several aromatase-inhibiting flavones in damiana ^{10Reference 10Zhao J et al. · 2008Anti-aromatase activity of the constituents from damiana (Turnera diffusa)View study →} — it is one contributor among many, not the demonstrated active principle.

Prevalence in Nature

Acacetin is a minor, taxonomically scattered flavone, found across the Asteraceae, Fabaceae and Lamiaceae. It is a documented flavonoid of the black locust tree (Robinia pseudoacacia), whose flowers and other tissues carry a range of acacetin and related flavonoid glycosides ^{14Reference 14Veitch NC et al. · 2010Flavonoid glycosides of the black locust tree, Robinia pseudoacacia (Leguminosae)View study →}; of chrysanthemum (Chrysanthemum morifolium) flowers, where it occurs largely as its 7-O-glycosides; of Korean mint (Agastache rugosa); of damiana (Turnera diffusa) leaves ^{10Reference 10Zhao J et al. · 2008Anti-aromatase activity of the constituents from damiana (Turnera diffusa)View study →}; and of dream herb (Calea zacatechichi). It is also reported from silver birch and other Asteraceae and Lamiaceae ^{13Reference 13Singh S et al. · 2020Acacetin, a flavone with diverse therapeutic potential in cancer, inflammation, infections and other metabolic disordersView study →}.

In plants the molecule is usually glycosylated rather than free — most commonly as the 7-O-rutinoside (linarin) or 7-O-glucoside. This has a useful practical corollary: acacetin (notably its 7-O-rutinoside) is used as a chemical marker to distinguish Chrysanthemum morifolium from the related C. indicum flower. Quantitative abundance across sources is not well characterised in the accessible literature, so no comparative concentration figures are given here.

Discovery & Synthesis

Acacetin takes its name from the genus Acacia, reflecting its early association with leguminous trees, and it is defined chemically as the 4’-O-methyl ether of apigenin. Its first precise isolation date is not clearly documented in the accessible literature; the compound was long known as a minor plant flavone before its modern research profile emerged in 2008 with the discovery of its atrial-selective ion-channel activity ^{1Reference 1Li GR et al. · 2008Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogsView study →}.

Synthesis today is straightforward flavone chemistry: acacetin is obtained by selective 4’-O-methylation of apigenin, or built by classical flavone routes (e.g. Baker–Venkataraman rearrangement / Allan–Robinson condensation) with a pre-methylated B-ring. The most consequential synthetic work on the molecule has been the deliberate design of a water-soluble prodrug to overcome its poor bioavailability for cardiac testing ^{3Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →}.

Patents: not yet researched.

Toxicity & Safety

Acacetin carries a low toxicity flag: it is a dietary flavone of foods and herbal teas (chrysanthemum, Korean mint), no notable acute toxicity is reported, and its poor oral bioavailability inherently limits systemic exposure. The caveats are about missing data and one mechanistic flag, not demonstrated harm.

Safety at a Glance

✅ Low / no toxicity

• A low-toxicity dietary flavone. Present in edible flowers and herbal teas at low levels; no notable acute-toxicity signal in the available literature.
• Poor oral bioavailability limits systemic exposure. The same pharmacokinetic weakness that frustrates its therapeutic use also caps incidental intake exposure ^{11Reference 11Han DG et al. · 2021AnimalInvestigation of the factors responsible for the poor oral bioavailability of acacetin in rats: physicochemical and biopharmaceutical aspectsView study →}.
• Aromatase (CYP19) inhibition in vitro. Acacetin inhibits estrogen-synthesising aromatase in enzyme assays (IC₅₀ ≈ 18.7 µM) — a theoretical endocrine-modulation flag worth noting for concentrated extracts, though not shown to matter at dietary intake ^{10Reference 10Zhao J et al. · 2008Anti-aromatase activity of the constituents from damiana (Turnera diffusa)View study →}.
• Human safety data are essentially absent. No clinical safety, drug-interaction or reproductive-toxicity dataset exists for the isolate; interactions with CYP enzymes and transporters have not been characterised in people.

Pregnancy and lactation decisions belong to the herb or product page where intake is actually decided, not to this molecule page; no isolate-specific reproductive dataset exists for acacetin, and no verdict is issued here.

Dosage

There is no established or recommended human dose for isolated acacetin. The figures in the literature are preclinical research doses — cell-culture concentrations (typically low-micromolar) and rodent/canine dosing, often delivered as a water-soluble prodrug rather than the parent compound because of its poor oral bioavailability ^{3,11Reference 3Liu H et al. · 2016Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogsView study →Reference 11Han DG et al. · 2021AnimalInvestigation of the factors responsible for the poor oral bioavailability of acacetin in rats: physicochemical and biopharmaceutical aspectsView study →}. Human exposure is dietary and indirect, as a minor glycosylated flavone of chrysanthemum tea, Korean mint and similar herbs. These are doses studied in research and are not a personal recommendation.

References

1. Li GR, Wang HB, Qin GW, et al. (2008). Acacetin, a natural flavone, selectively inhibits human atrial repolarization potassium currents and prevents atrial fibrillation in dogs. Circulation. https://pubmed.ncbi.nlm.nih.gov/18458165/
2. Wu HJ, Wu W, Sun HY, et al. (2011). Acacetin causes a frequency- and use-dependent blockade of hKv1.5 channels by binding to the S6 domain of the channel pore. Journal of Molecular and Cellular Cardiology. https://pubmed.ncbi.nlm.nih.gov/21906601/
3. Liu H, Wang YJ, Yang L, et al. (2016). Synthesis of a highly water-soluble acacetin prodrug for treating experimental atrial fibrillation in beagle dogs. Scientific Reports. https://pubmed.ncbi.nlm.nih.gov/27160397/
4. Tanigawa N, Hagiwara M, Tada H, et al. (2013). Acacetin inhibits expression of E-selectin on endothelial cells through regulation of the MAP kinase signaling pathway and activation of NF-κB. Immunopharmacology and Immunotoxicology. https://pubmed.ncbi.nlm.nih.gov/23855486/
5. Ha SK, Moon E, Lee P, et al. (2012). Acacetin attenuates neuroinflammation via regulation the response to LPS stimuli in vitro and in vivo. Neurochemical Research. https://pubmed.ncbi.nlm.nih.gov/22447574/
6. Kim CD, Cha JD, Li S, Cha IH (2015). The mechanism of acacetin-induced apoptosis on oral squamous cell carcinoma. Archives of Oral Biology. https://pubmed.ncbi.nlm.nih.gov/26099663/
7. Sun F, Li D, Wang C, et al. (2019). Acacetin-induced cell apoptosis in head and neck squamous cell carcinoma cells: evidence for the role of a mitochondria-dependent pathway. Phytotherapy Research. https://pubmed.ncbi.nlm.nih.gov/31066474/
8. Liu Y, et al. (2024). Acacetin inhibits activation of microglia to improve neuroinflammation after subarachnoid hemorrhage. Human & Experimental Toxicology. https://pubmed.ncbi.nlm.nih.gov/38720657/
9. Kwon EB, Kang MJ, Ryu HW, et al. (2020). Acacetin enhances glucose uptake through insulin-independent GLUT4 translocation in L6 myotubes. Phytomedicine. https://pubmed.ncbi.nlm.nih.gov/32126492/
10. Zhao J, Dasmahapatra AK, Khan SI, Khan IA (2008). Anti-aromatase activity of the constituents from damiana (Turnera diffusa). Journal of Ethnopharmacology. https://pubmed.ncbi.nlm.nih.gov/18948180/
11. Han DG, Cha E, Joo J, Hwang JS, et al. (2021). Investigation of the factors responsible for the poor oral bioavailability of acacetin in rats: physicochemical and biopharmaceutical aspects. Pharmaceutics. https://pubmed.ncbi.nlm.nih.gov/33525442/
12. Dai P, Luo F, Wang Y, et al. (2015). Triple recycling processes impact systemic and local bioavailability of orally administered flavonoids (acacetin). The AAPS Journal. https://pubmed.ncbi.nlm.nih.gov/25762448/
13. Singh S, Gupta P, Meena A, Luqman S (2020). Acacetin, a flavone with diverse therapeutic potential in cancer, inflammation, infections and other metabolic disorders. Food and Chemical Toxicology. https://pubmed.ncbi.nlm.nih.gov/32866514/
14. Veitch NC, Elliott PC, Kite GC, Lewis GP (2010). Flavonoid glycosides of the black locust tree, Robinia pseudoacacia (Leguminosae). Phytochemistry. https://pubmed.ncbi.nlm.nih.gov/19948349/

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