Quercetagetin

Quercetagetin at a Glance

Quercetagetin is a flavonol — specifically 6-hydroxyquercetin, i.e. quercetin carrying an extra hydroxyl group at the 6-position (systematic name 3,5,6,7,3’,4’-hexahydroxyflavone). It is the characteristic yellow flavonol pigment of marigold (Tagetes) flowers and is also reported in immature citrus peel ^{7,9Reference 7Wang W et al. · 2016In vitroIn vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residuesView study →Reference 9Zhang H et al. · 2025Systematic reviewA systematic review on the research status of quercetagetin: resources, biosynthesis, bioavailability, bioactive-delivery systems, health effects, marketed functional products and patentsView study →}.

Its pharmacology is entirely preclinical. The isolated molecule has two unusually specific enzyme activities for a plant flavonol — it is a moderately potent, ATP-competitive Pim-1 kinase inhibitor ^{3Reference 3Holder S et al. · 2007Characterization of a potent and selective small-molecule inhibitor of the PIM1 kinaseView study →} and a tyrosinase inhibitor ^{4Reference 4Liang F · 2024Inhibition mechanism investigation of quercetagetin as a potential tyrosinase inhibitorView study →} — alongside the anti-inflammatory and antioxidant behaviour typical of the flavonol class ^{5,6,7Reference 5Wang H et al. · 2025Quercetagetin alleviates inflammatory osteoclastogenesis and collagen antibody-induced arthritis via Nrf2 signaling and Pten/AKT/Nfatc1 axisView study →Reference 6Kang GJ et al. · 2013Anti-inflammatory effect of quercetagetin, an active component of immature Citrus unshiu, in HaCaT human keratinocytesView study →Reference 7Wang W et al. · 2016In vitroIn vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residuesView study →}. There are no human trials.

The honest headline is a chemical caveat: quercetagetin carries a B-ring catechol and an A-ring 5,6,7-trihydroxy (pyrogallol-type) motif, which makes it strongly reducing but also prone to autoxidation in neutral aqueous solution — a source of both its antioxidant readings and a stability/pro-oxidant liability ^{8,10Reference 8Bulut O · 2021Concise synthesis of quercetagetin (3,3’,4’,5,6,7-hexahydroxyflavone) with antioxidant and antibacterial activitiesView study →Reference 10Hodnick WF et al. · 1994Inhibition of mitochondrial respiration and cyanide-stimulated generation of reactive oxygen species by selected flavonoidsView study →}.

Quercetagetin vs. Quercetin & Patuletin

The whole page turns on one added hydroxyl. Quercetagetin is quercetin plus a 6-OH group on the A-ring; its close relative patuletin is the 6-methyl ether of that same position (6-methoxyquercetin). So the three form a small, informative series:

• Quercetin — 3,5,7,3’,4’-pentahydroxyflavone (no 6-substituent); the abundant dietary parent.
• Quercetagetin — quercetin + 6-OH; the marigold pigment. The free 6-OH gives it an A-ring pyrogallol arrangement (5,6,7-trihydroxy), raising its metal-chelating and radical activity but also its autoxidation.
• Patuletin — the 6-O-methyl version; capping the 6-OH removes that pyrogallol reactivity.

That extra 6-oxygenation is not cosmetic. It is what lets quercetagetin fit the Pim-1 ATP pocket well enough to inhibit it selectively ^{3Reference 3Holder S et al. · 2007Characterization of a potent and selective small-molecule inhibitor of the PIM1 kinaseView study →}, and its catechol/pyrogallol hydroxyls are what chelate the copper in tyrosinase ^{4Reference 4Liang F · 2024Inhibition mechanism investigation of quercetagetin as a potential tyrosinase inhibitorView study →} — while also being the groups that oxidise. In several assays quercetagetin out-performs quercetin (e.g. it was the more potent anti-inflammatory of the two in keratinocytes ^{6Reference 6Kang GJ et al. · 2013Anti-inflammatory effect of quercetagetin, an active component of immature Citrus unshiu, in HaCaT human keratinocytesView study →}).

What It's Used For

Everything below is in-vitro or animal work on the isolated molecule or a marigold extract; none of it is human-validated.

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. Every row here is preclinical (no human data), so the ceiling is low by design; read the per-row basis.

01Pim-1 Kinase Inhibition (Anticancer Lead)Shaky42%Isolated-molecule enzyme + prostate-cancer cell data; potent, selective, ATP-competitive ^{3Reference 3Holder S et al. · 2007Characterization of a potent and selective small-molecule inhibitor of the PIM1 kinaseView study →}

02Anti-InflammatoryShaky38%In-vitro keratinocyte mechanism ^{6Reference 6Kang GJ et al. · 2013Anti-inflammatory effect of quercetagetin, an active component of immature Citrus unshiu, in HaCaT human keratinocytesView study →} + an in-vivo mouse arthritis model ^{5Reference 5Wang H et al. · 2025Quercetagetin alleviates inflammatory osteoclastogenesis and collagen antibody-induced arthritis via Nrf2 signaling and Pten/AKT/Nfatc1 axisView study →}

03Tyrosinase Inhibition (Skin Depigmentation)Shaky32%Single isolated-enzyme study, mechanism well-characterised ^{4Reference 4Liang F · 2024Inhibition mechanism investigation of quercetagetin as a potential tyrosinase inhibitorView study →}

04Antioxidant / Metal ChelationShaky28%In-vitro radical-scavenging + chelation of extract/isolate ^{7Reference 7Wang W et al. · 2016In vitroIn vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residuesView study →}; confounded by autoxidation ^{8,10Reference 8Bulut O · 2021Concise synthesis of quercetagetin (3,3’,4’,5,6,7-hexahydroxyflavone) with antioxidant and antibacterial activitiesView study →Reference 10Hodnick WF et al. · 1994Inhibition of mitochondrial respiration and cyanide-stimulated generation of reactive oxygen species by selected flavonoidsView study →}

Mechanisms

The load-bearing point: the 6-OH-created A-ring pyrogallol is simultaneously what sharpens the metal-chelation/antioxidant chemistry and what makes the molecule autoxidise — potency and instability come from the same feature.

Pharmacokinetics

Quercetagetin’s human pharmacokinetics are not characterised. By close analogy to quercetin — and as flagged in the compound’s systematic review — an ingested flavonol aglycone of this type is expected to have low oral bioavailability, extensive phase-II (glucuronide/sulfate) conjugation and rapid clearance, which is precisely why delivery systems (encapsulation, nanoformulation) are being explored for it ^{9Reference 9Zhang H et al. · 2025Systematic reviewA systematic review on the research status of quercetagetin: resources, biosynthesis, bioavailability, bioactive-delivery systems, health effects, marketed functional products and patentsView study →}. Compounding this, the free 6-OH/catechol makes quercetagetin chemically unstable in neutral aqueous conditions, autoxidising to quinones with superoxide/H2O2 release ^{8Reference 8Bulut O · 2021Concise synthesis of quercetagetin (3,3’,4’,5,6,7-hexahydroxyflavone) with antioxidant and antibacterial activitiesView study →}. Both facts mean the sub-micromolar Pim-1 and sub-millimolar tyrosinase potencies seen in vitro should not be assumed to translate to systemic exposure in vivo.

Clinical Trials

There are no clinical trials of quercetagetin. The entire evidence base is enzyme assays, cell work and a single rodent arthritis model.

Last checked: July 2026.

The Autoxidation Caveat

Quercetagetin is a useful cautionary example of why a high antioxidant reading is not automatically a good thing. Redox-active flavonols with catechol and pyrogallol hydroxylation — a group that includes quercetagetin, quercetin and myricetin — autoxidise in neutral aqueous buffer, consuming oxygen and producing superoxide (O2-) and hydrogen peroxide (H2O2) along with semiquinone and quinone species ^{8,10Reference 8Bulut O · 2021Concise synthesis of quercetagetin (3,3’,4’,5,6,7-hexahydroxyflavone) with antioxidant and antibacterial activitiesView study →Reference 10Hodnick WF et al. · 1994Inhibition of mitochondrial respiration and cyanide-stimulated generation of reactive oxygen species by selected flavonoidsView study →}. Quercetagetin is especially exposed because its 6-OH gives the A-ring a 5,6,7-trihydroxy (pyrogallol) arrangement on top of the usual B-ring catechol.

Practically this means: (1) some “antioxidant” assay signal is the molecule oxidising itself rather than protecting a target; (2) under the wrong conditions (neutral pH, transition-metal traces) the same chemistry can turn pro-oxidant; and (3) formulations must protect it. It does not make quercetagetin dangerous at dietary levels, but it is the reason its bench potency and its real-world usefulness can diverge.

Its Role in Plants

Quercetagetin is a flower pigment. It accumulates as the free flavonol and as glycosides (e.g. quercetagetin-7-O-glucoside) in the ray florets and petals of Tagetes, contributing to their deep yellow-orange colouration and to UV-protective / antioxidant defence ^{1,9Reference 1Kim JH et al. · 2022Changes in quercetin derivatives and antioxidant activity in marigold petals (Tagetes patula L.) induced by ultraviolet-B irradiation and methyl jasmonateView study →Reference 9Zhang H et al. · 2025Systematic reviewA systematic review on the research status of quercetagetin: resources, biosynthesis, bioavailability, bioactive-delivery systems, health effects, marketed functional products and patentsView study →}. Its defining 6-hydroxylation is installed by a dedicated flavonol 6-hydroxylase, a cytochrome-P450-type enzyme characteristic of Tagetes, acting on the quercetin skeleton to add the C6 hydroxyl ^{9Reference 9Zhang H et al. · 2025Systematic reviewA systematic review on the research status of quercetagetin: resources, biosynthesis, bioavailability, bioactive-delivery systems, health effects, marketed functional products and patentsView study →}. Petal quercetagetin levels are stress-responsive — UV-B exposure and methyl-jasmonate treatment shift the quercetin-derivative profile in marigold petals ^{1Reference 1Kim JH et al. · 2022Changes in quercetin derivatives and antioxidant activity in marigold petals (Tagetes patula L.) induced by ultraviolet-B irradiation and methyl jasmonateView study →}.

These are plant-pigment and plant-defence functions and should not be read as human pharmacology.

Prevalence in Nature

Quercetagetin is best known as the signature flavonol of the genus Tagetes (marigolds), occurring in Tagetes erecta (African/Aztec marigold), T. patula (French marigold), T. lucida (Mexican tarragon / yerbaniz) and T. minuta ^{1,2,7Reference 1Kim JH et al. · 2022Changes in quercetin derivatives and antioxidant activity in marigold petals (Tagetes patula L.) induced by ultraviolet-B irradiation and methyl jasmonateView study →Reference 2Aquino R et al. · 2002An extract of Tagetes lucida and its phenolic constituents as antioxidantsView study →Reference 7Wang W et al. · 2016In vitroIn vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residuesView study →}. In T. erecta it is recovered in quantity from the lutein-extracted inflorescence residues, making it a by-product of the marigold-carotenoid industry ^{7Reference 7Wang W et al. · 2016In vitroIn vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residuesView study →}. Beyond the marigolds it is reported in immature Citrus unshiu (satsuma) peel, where it is the primary anti-inflammatory flavonol of the extract ^{6Reference 6Kang GJ et al. · 2013Anti-inflammatory effect of quercetagetin, an active component of immature Citrus unshiu, in HaCaT human keratinocytesView study →}, and in other Asteraceae such as Flourensia oolepis. Reliable percent-dry-weight figures across these sources are not well tabulated, which is why no Content-by-Source chart is drawn here.

Discovery & Synthesis

Quercetagetin (CAS 90-18-6) has long been recognised as the characteristic flavonol pigment of marigold flowers, from which it is conventionally obtained by extraction — historically as a co-product of Tagetes processing for xanthophyll/lutein pigments. Because it is a fully hydroxylated flavonol it is not usually made industrially by synthesis; the isolation-from-marigold route dominates ^{7,9Reference 7Wang W et al. · 2016In vitroIn vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residuesView study →Reference 9Zhang H et al. · 2025Systematic reviewA systematic review on the research status of quercetagetin: resources, biosynthesis, bioavailability, bioactive-delivery systems, health effects, marketed functional products and patentsView study →}.

A concise laboratory total synthesis was reported by Bulut and Yilmaz in 2021 (Results in Chemistry), assembling 3,5,6,7,3’,4’-hexahydroxyflavone and confirming antioxidant and antibacterial activity of the synthetic material — useful for supplying defined, high-purity quercetagetin for research where the plant-extracted molecule’s variability and autoxidation are problematic ^{8Reference 8Bulut O · 2021Concise synthesis of quercetagetin (3,3’,4’,5,6,7-hexahydroxyflavone) with antioxidant and antibacterial activitiesView study →}. A 2025 systematic review catalogues its resources, biosynthesis, bioavailability and emerging delivery systems ^{9Reference 9Zhang H et al. · 2025Systematic reviewA systematic review on the research status of quercetagetin: resources, biosynthesis, bioavailability, bioactive-delivery systems, health effects, marketed functional products and patentsView study →}.

Patents: not yet researched.

Toxicity & Safety

Quercetagetin carries a low toxicity flag: it is a minor dietary flavonol of edible marigold and citrus material, consumed by people for centuries at low levels with no signal of harm, and no acute toxicity has been reported for the amounts encountered in food. As with the whole flavonol class, a dedicated human safety, genotoxicity or reproductive-toxicity dataset has not been characterised for the isolated molecule, so absence of evidence is not evidence of safety at supplement-scale doses.

Safety at a Glance

✅ Low / no toxicity

• Low-concern dietary flavonol. Present in edible marigold and citrus-peel material at low levels with no reported acute toxicity.
• Chemically unstable / potentially pro-oxidant. Autoxidises in neutral aqueous solution, generating superoxide and H2O2; under metal-rich conditions its antioxidant chemistry can flip pro-oxidant.
• No human safety data. No clinical, genotoxicity or reproductive-toxicity characterisation of the isolate; interactions and high-dose effects are unstudied.
• Metal chelation is double-edged. Its avid iron/copper chelation underlies both its antioxidant readings and its enzyme inhibition, and could in principle affect metal handling at high intake — untested in humans.

Dosage

There is no established human dose for quercetagetin. It has been studied only in the laboratory: as an isolated molecule in enzyme and cell assays (Pim-1 kinase IC50 ~0.34 uM ^{3Reference 3Holder S et al. · 2007Characterization of a potent and selective small-molecule inhibitor of the PIM1 kinaseView study →}; tyrosinase IC50 ~0.19 mM ^{4Reference 4Liang F · 2024Inhibition mechanism investigation of quercetagetin as a potential tyrosinase inhibitorView study →}; DPPH/ABTS antioxidant IC50 in the low-micromolar range ^{7Reference 7Wang W et al. · 2016In vitroIn vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residuesView study →}) and at 40 mg/kg/day in a mouse arthritis model ^{5Reference 5Wang H et al. · 2025Quercetagetin alleviates inflammatory osteoclastogenesis and collagen antibody-induced arthritis via Nrf2 signaling and Pten/AKT/Nfatc1 axisView study →}. Human dietary exposure is indirect, from marigold-flower and citrus-peel material, at uncharacterised levels. These are research figures, not a personal recommendation.

References

1. Kim JH, Duan S, Lim YJ, Eom SH (2022). Changes in quercetin derivatives and antioxidant activity in marigold petals (Tagetes patula L.) induced by ultraviolet-B irradiation and methyl jasmonate. Plants (Basel). https://pubmed.ncbi.nlm.nih.gov/36365399/
2. Aquino R, Cáceres A, Morelli S, Rastrelli L (2002). An extract of Tagetes lucida and its phenolic constituents as antioxidants. Journal of Natural Products. https://pubmed.ncbi.nlm.nih.gov/12502312/
3. Holder S, Zemskova M, Zhang C, Tabrizizad M, Bremer R, Neidigh JW, Lilly MB (2007). Characterization of a potent and selective small-molecule inhibitor of the PIM1 kinase. Molecular Cancer Therapeutics. https://pubmed.ncbi.nlm.nih.gov/17218638/
4. Liang F (2024). Inhibition mechanism investigation of quercetagetin as a potential tyrosinase inhibitor. Frontiers in Chemistry. https://pubmed.ncbi.nlm.nih.gov/38894729/
5. Wang H, Yuan T, Wang J, Li D, Lee WY, Li Z, Sun S (2025). Quercetagetin alleviates inflammatory osteoclastogenesis and collagen antibody-induced arthritis via Nrf2 signaling and Pten/AKT/Nfatc1 axis. Arthritis Research & Therapy. https://pubmed.ncbi.nlm.nih.gov/40057805/
6. Kang GJ, Han SC, Ock JW, Kang HK, Yoo ES (2013). Anti-inflammatory effect of quercetagetin, an active component of immature Citrus unshiu, in HaCaT human keratinocytes. Biomolecules & Therapeutics (Seoul). https://pubmed.ncbi.nlm.nih.gov/24009872/
7. Wang W, Xu H, Chen H, Tai K, Liu F, Gao Y (2016). In vitro antioxidant, anti-diabetic and antilipemic potentials of quercetagetin extracted from marigold (Tagetes erecta L.) inflorescence residues. Journal of Food Science and Technology. https://pubmed.ncbi.nlm.nih.gov/27478217/
8. Bulut O, Yilmaz MD (2021). Concise synthesis of quercetagetin (3,3’,4’,5,6,7-hexahydroxyflavone) with antioxidant and antibacterial activities. Results in Chemistry. https://doi.org/10.1016/j.rechem.2021.100255
9. Zhang H, Farag MA, Cao H, et al. (2025). A systematic review on the research status of quercetagetin: resources, biosynthesis, bioavailability, bioactive-delivery systems, health effects, marketed functional products and patents. Phytochemistry Reviews. https://doi.org/10.1007/s11101-025-10078-w
10. Hodnick WF, Duval DL, Pardini RS (1994). Inhibition of mitochondrial respiration and cyanide-stimulated generation of reactive oxygen species by selected flavonoids. Biochemical Pharmacology. https://pubmed.ncbi.nlm.nih.gov/8117326/

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