Eriodictyol

Eriodictyol at a Glance

Eriodictyol is a flavanone — 5,7,3’,4’-tetrahydroxyflavanone — first characterised from and named after yerba santa (Eriodictyon californicum), whose genus gives the molecule its name. It also occurs as a minor flavanone in citrus peel (the aglycone of the glycoside eriocitrin) and, at low levels, across many other plants ^{1Reference 1Deng Z et al. · 2020Pharmacological activity of eriodictyol: the major natural polyphenolic flavanoneView study →}.

Its clearest identity in the research literature is as a cytoprotective antioxidant: eriodictyol is a well-documented activator of the Nrf2/HO-1 antioxidant pathway, and most of its preclinical pharmacology — anti-inflammatory, anti-allergic and chemopreventive signals — traces back to that redox and inflammatory modulation ^{1,2Reference 1Deng Z et al. · 2020Pharmacological activity of eriodictyol: the major natural polyphenolic flavanoneView study →Reference 2Habtemariam S · 2019The Nrf2/HO-1 axis as targets for flavanones: neuroprotection by pinocembrin, naringenin, and eriodictyolView study →}. Structurally it is also the parent of two of yerba santa’s better-known flavanones: sterubin and homoeriodictyol are both O-methyl ethers of eriodictyol.

The honest headline is that eriodictyol’s evidence is almost entirely preclinical — cell and rodent models of the isolated molecule, with no human trials of eriodictyol itself. As a minor dietary flavanone it carries a low intrinsic-risk profile, but that reflects class chemistry and food exposure rather than a dedicated safety dossier.

Eriodictyol, Sterubin & Homoeriodictyol

Eriodictyol is the parent flavanone of the yerba-santa flavanone family, and the relationship is the tidiest way to understand why its methylated relatives behave differently. Both siblings are monomethyl ethers of eriodictyol — they differ only in which hydroxyl is capped:

• Sterubin is (2S)-7-O-methyleriodictyol — methylated on the A-ring 7-hydroxyl, so it retains the intact 3’,4’-catechol B-ring. That preserved catechol is why sterubin, not the other two, carries the potent Nrf2/antioxidant/iron-chelating neuroprotective activity identified in Salk Institute Alzheimer’s screening ^{1Reference 1Deng Z et al. · 2020Pharmacological activity of eriodictyol: the major natural polyphenolic flavanoneView study →}.
• Homoeriodictyol is the 3’-O-methyl ether — methylated on the B-ring, which breaks the catechol. Its fame is not therapeutic but sensory: as its sodium salt it is a commercial bitter-masking flavour ingredient ^{9Reference 9Ley JP et al. · 2005Evaluation of bitter-masking flavanones from Herba Santa (Eriodictyon californicum)View study →}.

Eriodictyol itself sits at the head of this series with a free, intact catechol B-ring — the structural feature associated with strong radical scavenging and Nrf2 induction. It is also one of the taste-active flavanones evaluated in yerba santa’s bitter-masking chemistry, though the commercial masker is the methylated homoeriodictyol, not eriodictyol ^{9Reference 9Ley JP et al. · 2005Evaluation of bitter-masking flavanones from Herba Santa (Eriodictyon californicum)View study →}. Reading the three pages together closes the yerba-santa flavanone family: one parent catechol flavanone (eriodictyol), one A-ring methyl ether that keeps the catechol and the potent neuro-activity (sterubin), and one B-ring methyl ether that trades it for taste-masking (homoeriodictyol).

Eriodictyol vs. Luteolin

Eriodictyol shares its exact hydroxylation pattern (5,7,3’,4’) with the flavone luteolin — the two are the flavanone and flavone versions of the same substitution. The only difference is the C-ring: eriodictyol is a flavanone (a saturated, chiral C2–C3 single bond with a stereocentre at C2), whereas luteolin is a flavone (a flat, planar C2=C3 double bond).

That one bond matters. The planar flavone geometry of luteolin generally makes it a more potent, more rigid ligand at many protein targets and a stronger literature presence, while eriodictyol’s saturated, non-planar flavanone ring makes it a softer, chiral molecule (it exists as R and S enantiomers, both antioxidant-active). In practice the two are studied for overlapping antioxidant and anti-inflammatory effects, but they are not interchangeable: luteolin is the flavone, eriodictyol its reduced flavanone relative, and each should be read on its own evidence.

Nrf2 Cytoprotection

If eriodictyol has a signature mechanism, it is activation of the Nrf2/ARE antioxidant response. Nrf2 (nuclear factor erythroid 2–related factor 2) is a master transcription factor that, once released and translocated to the nucleus, switches on a battery of cytoprotective genes — most notably heme oxygenase-1 (HO-1) and γ-glutamylcysteine synthetase (γ-GCS), the rate-limiting enzyme for glutathione synthesis.

In neuron-like PC12 cells, eriodictyol induced Nrf2 nuclear translocation, up-regulated HO-1 and γ-GCS, raised intracellular glutathione, and protected against hydrogen-peroxide-induced death — an effect abolished when HO-1 was inhibited or knocked down, pinning the protection to that axis ^{3Reference 3Lou H et al. · 2012Eriodictyol protects against H₂O₂-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathwayView study →}. The same cascade recurs across models: eriodictyol protected against arsenic-trioxide liver injury in mice by activating Nrf2 ^{4Reference 4Xie G et al. · 2017Eriodictyol attenuates arsenic trioxide-induced liver injury by activation of Nrf2View study →}, and reduced high-glucose oxidative stress and inflammation in retinal ganglion cells through Nrf2/HO-1 ^{5Reference 5Lv P et al. · 2019Eriodictyol inhibits high glucose-induced oxidative stress and inflammation in retinal ganglial cellsView study →}. This is the through-line beneath most of eriodictyol’s downstream anti-inflammatory and chemopreventive signals: it is fundamentally a redox-modulating, cytoprotective flavanone, with the intact catechol B-ring doing the chemical work.

What It's Used For

Beyond the Nrf2 mechanism, eriodictyol’s evidence splits into three preclinical threads — antioxidant/cytoprotective, anti-inflammatory/anti-allergic, and chemopreventive — all tested on the isolated molecule in cell or rodent models.

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 human data exists for eriodictyol, so scores stay low by design despite the mechanistic depth.

01Antioxidant / Nrf2 CytoprotectionShaky42%Isolate Nrf2/HO-1 mechanism across neuronal, hepatic, retinal cell/rodent models ^{3,4,5Reference 3Lou H et al. · 2012Eriodictyol protects against H₂O₂-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathwayView study →Reference 4Xie G et al. · 2017Eriodictyol attenuates arsenic trioxide-induced liver injury by activation of Nrf2View study →Reference 5Lv P et al. · 2019Eriodictyol inhibits high glucose-induced oxidative stress and inflammation in retinal ganglial cellsView study →}

02Anti-Inflammatory / Anti-AllergicShaky32%Mast-cell/CERK inhibition + NLRP3 (isolate, cell + mouse) ^{6,7Reference 6Yoo JM et al. · 2012Inhibitory effect of eriodictyol on IgE/Ag-induced type I hypersensitivityView study →Reference 7Guo P et al. · 2022AnimalEriodictyol and homoeriodictyol improve memory impairment in Aβ(25–35)-induced mice by inhibiting the NLRP3 inflammasomeView study →}

03Chemopreventive / AnticancerShaky24%Rat colon-carcinogenesis model + carcinogen-metabolism inhibition in the Eriodictyon flavonoid screen ^{8,10Reference 8Mariyappan P et al. · 2017Effect of eriodictyol on preneoplastic lesions, oxidative stress and bacterial enzymes in 1,2-dimethylhydrazine-induced colon carcinogenesisView study →Reference 10Liu YL et al. · 1992Isolation of potential cancer-chemopreventive agents from Eriodictyon californicumView study →}

Mechanisms

Only the Nrf2/HO-1 axis is established across several independent models; the CERK, NLRP3 and carcinogen-metabolism findings are each single-context results.

Pharmacokinetics

Eriodictyol is a flavanone aglycone with poor oral bioavailability. In a stereoselective rat pharmacokinetic study it underwent rapid and extensive phase-II metabolism (glucuronidation/sulfation) with predominantly non-renal elimination and short serum half-lives, the classic profile of a citrus-type flavanone ^{11Reference 11Yáñez JA et al. · 2008AnimalPharmacokinetics of selected chiral flavonoids: hesperetin, naringenin and eriodictyol in rats and their content in fruit juicesView study →}. As a chiral molecule it exists as R and S enantiomers, both of which are antioxidant-active ^{1Reference 1Deng Z et al. · 2020Pharmacological activity of eriodictyol: the major natural polyphenolic flavanoneView study →}. No dedicated human pharmacokinetic study of eriodictyol exists; in food it is largely present as the glycoside eriocitrin, which must be deglycosylated before the aglycone is absorbed. The practical consequence is a large gap between in-vitro potency and achievable plasma levels, which should be held against every cell-based claim above.

Clinical Trials

There are no clinical trials of isolated eriodictyol — none completed, ongoing, planned or terminated. All efficacy evidence is cell-based or rodent (mast-cell/hypersensitivity ^{6Reference 6Yoo JM et al. · 2012Inhibitory effect of eriodictyol on IgE/Ag-induced type I hypersensitivityView study →}, Aβ memory ^{7Reference 7Guo P et al. · 2022AnimalEriodictyol and homoeriodictyol improve memory impairment in Aβ(25–35)-induced mice by inhibiting the NLRP3 inflammasomeView study →}, colon carcinogenesis ^{8Reference 8Mariyappan P et al. · 2017Effect of eriodictyol on preneoplastic lesions, oxidative stress and bacterial enzymes in 1,2-dimethylhydrazine-induced colon carcinogenesisView study →}, and the Nrf2 cytoprotection models ^{3,4,5Reference 3Lou H et al. · 2012Eriodictyol protects against H₂O₂-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathwayView study →Reference 4Xie G et al. · 2017Eriodictyol attenuates arsenic trioxide-induced liver injury by activation of Nrf2View study →Reference 5Lv P et al. · 2019Eriodictyol inhibits high glucose-induced oxidative stress and inflammation in retinal ganglial cellsView study →}).

Last checked: July 2026.

Isolate vs. Plant Studies

Eriodictyol’s evidence base is unusually isolate-heavy — which cuts both ways. The Nrf2/HO-1, mast-cell and chemoprevention studies all use the purified molecule, so they genuinely test eriodictyol rather than a mixed extract ^{3,4,6,8Reference 3Lou H et al. · 2012Eriodictyol protects against H₂O₂-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathwayView study →Reference 4Xie G et al. · 2017Eriodictyol attenuates arsenic trioxide-induced liver injury by activation of Nrf2View study →Reference 6Yoo JM et al. · 2012Inhibitory effect of eriodictyol on IgE/Ag-induced type I hypersensitivityView study →Reference 8Mariyappan P et al. · 2017Effect of eriodictyol on preneoplastic lesions, oxidative stress and bacterial enzymes in 1,2-dimethylhydrazine-induced colon carcinogenesisView study →}. But they are also all preclinical, and the isolate’s poor oral bioavailability means cell-dish concentrations are unlikely to be reached from diet or a whole-herb preparation ^{11Reference 11Yáñez JA et al. · 2008AnimalPharmacokinetics of selected chiral flavonoids: hesperetin, naringenin and eriodictyol in rats and their content in fruit juicesView study →}. Where eriodictyol appears as a plant constituent, it is one contributor among many: it is named (with epicatechin) in the polyphenol-rich, gastroprotective resin of Virola oleifera ^{13Reference 13Pereira ACH et al. · 2017Gastroprotective activity of the resin from Virola oleiferaView study →}, and it sits within the yerba-santa flavonoid fraction whose historical chemoprevention activity was shared across a dozen flavonoids ^{10Reference 10Liu YL et al. · 1992Isolation of potential cancer-chemopreventive agents from Eriodictyon californicumView study →}. In yerba santa specifically, the potent neuro-activity belongs to the methylated relative sterubin, not to eriodictyol ^{12Reference 12Shock CC et al. · 2026Chemical composition of Eriodictyon californicum (California yerba santa) cultivated in Ontario, Oregon, USAView study →}.

Prevalence in Nature

Eriodictyol is a widespread minor flavanone. Its defining source is yerba santa (Eriodictyon californicum), the plant it is named after, where it occurs alongside its methyl ethers homoeriodictyol and sterubin and the taste-active prenylated benzoic acids ^{9,12Reference 9Ley JP et al. · 2005Evaluation of bitter-masking flavanones from Herba Santa (Eriodictyon californicum)View study →Reference 12Shock CC et al. · 2026Chemical composition of Eriodictyon californicum (California yerba santa) cultivated in Ontario, Oregon, USAView study →}. It is also a citrus-peel flavanone — the aglycone of the glycoside eriocitrin, found in lemons and other Citrus species — and appears at low levels across many other plant families ^{1Reference 1Deng Z et al. · 2020Pharmacological activity of eriodictyol: the major natural polyphenolic flavanoneView study →}.

It turns up as a constituent of other medicinal plants too: it is one of the phenolics identified (with epicatechin) in the polyphenol-rich (~82%) resin of epena (Virola oleifera), where the whole resin is gastroprotective ^{13Reference 13Pereira ACH et al. · 2017Gastroprotective activity of the resin from Virola oleiferaView study →}. Quantified concentrations for eriodictyol specifically are sparse — the detailed yerba-santa chemotype work quantifies sterubin, homoeriodictyol and the eriolic acids rather than the parent eriodictyol ^{12Reference 12Shock CC et al. · 2026Chemical composition of Eriodictyon californicum (California yerba santa) cultivated in Ontario, Oregon, USAView study →} — so its abundance is best described qualitatively as minor but widespread.

Discovery & Synthesis

Eriodictyol takes its name directly from yerba santa’s genus, Eriodictyon, from which the flavanone was characterised — the etymology is the clearest fact in its history. The precise primary-isolation report is not documented in the sources reviewed here, and should be treated as a gap to confirm on a later pass rather than stated with false confidence. Its structure — 5,7,3’,4’-tetrahydroxyflavanone, the flavanone counterpart of the flavone luteolin — is well established, and it is a chiral molecule obtained in nature and in synthesis as a mix or single enantiomers ^{1Reference 1Deng Z et al. · 2020Pharmacological activity of eriodictyol: the major natural polyphenolic flavanoneView study →}.

Manufacture today is chiefly by extraction/semi-synthesis from citrus-derived flavanone precursors (eriocitrin/hesperidin chemistry) rather than large-scale total synthesis; it is available as a research-grade fine chemical. A full production and enantioselective-synthesis account was not resolved here.

Patents: not yet researched.

Toxicity & Safety

Eriodictyol carries a low flag, consistent with its sibling yerba-santa flavanones. It is a minor dietary flavanone of citrus and edible plants with no isolate toxicity signal reported in the preclinical studies above — but that low flag reflects class chemistry and food-level exposure, not a dedicated safety dossier.

Safety at a Glance

✅ Low / no toxicity

• Minor dietary flavanone. Consumed as a natural constituent of citrus peel and yerba-santa preparations, with no overt toxicity reported in preclinical studies.
• No human safety data for the isolate. No chronic-toxicity, genotoxicity or clinical dataset exists for eriodictyol as a supplement.
• Poor oral bioavailability and unassessed interactions. Extensive phase-II metabolism; drug-interaction and pregnancy/lactation risks are not characterised for the isolate.

Full Safety & Interactions Detail

Eriodictyol’s low flag rests on class-chemistry and dietary-exposure grounds: it is a minor flavanone of citrus and edible plants, and the rodent efficacy studies dosed the isolate without reporting overt toxicity ^{4,8Reference 4Xie G et al. · 2017Eriodictyol attenuates arsenic trioxide-induced liver injury by activation of Nrf2View study →Reference 8Mariyappan P et al. · 2017Effect of eriodictyol on preneoplastic lesions, oxidative stress and bacterial enzymes in 1,2-dimethylhydrazine-induced colon carcinogenesisView study →}.

There is no dedicated chronic-toxicity, genotoxicity or human safety dataset for isolated eriodictyol, so the low flag reflects short-term animal exposure and food-level intake rather than a full dossier. As a catechol flavanone it is subject to the usual phase-II conjugation (glucuronidation/sulfation) ^{11Reference 11Yáñez JA et al. · 2008AnimalPharmacokinetics of selected chiral flavonoids: hesperetin, naringenin and eriodictyol in rats and their content in fruit juicesView study →}; specific cytochrome-P450 or transporter interactions have not been characterised, so herb-drug interaction risk is unassessed rather than ruled out.

Reproductive note (prose only). No reproductive or developmental-toxicity dataset exists for isolated eriodictyol. Pregnancy and lactation decisions belong to the herb or product page where intake is decided, not to this molecule page — incidental dietary/flavour-level exposure is presumably low-concern, but isolated or supplemental use is uncharacterised.

Dosage

There is no established therapeutic dose for eriodictyol — there is nothing validated to dose for. All efficacy data are preclinical (cell and rodent) ^{3,6,8Reference 3Lou H et al. · 2012Eriodictyol protects against H₂O₂-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathwayView study →Reference 6Yoo JM et al. · 2012Inhibitory effect of eriodictyol on IgE/Ag-induced type I hypersensitivityView study →Reference 8Mariyappan P et al. · 2017Effect of eriodictyol on preneoplastic lesions, oxidative stress and bacterial enzymes in 1,2-dimethylhydrazine-induced colon carcinogenesisView study →}, and the isolate’s poor oral bioavailability makes whole-herb or dietary intake an unreliable route to any defined systemic level ^{11Reference 11Yáñez JA et al. · 2008AnimalPharmacokinetics of selected chiral flavonoids: hesperetin, naringenin and eriodictyol in rats and their content in fruit juicesView study →}. Dietary exposure from citrus and yerba-santa preparations is incidental and low. No supplement dosing is warranted or supported by the current evidence — these are research observations, not a personal recommendation.

References

1. Deng Z, et al. (2020). Pharmacological activity of eriodictyol: the major natural polyphenolic flavanone. Evidence-Based Complementary and Alternative Medicine. https://pubmed.ncbi.nlm.nih.gov/33414838/
2. Habtemariam S (2019). The Nrf2/HO-1 axis as targets for flavanones: neuroprotection by pinocembrin, naringenin, and eriodictyol. Oxidative Medicine and Cellular Longevity. https://pubmed.ncbi.nlm.nih.gov/31814878/
3. Lou H, et al. (2012). Eriodictyol protects against H₂O₂-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathway. Neurochemistry International. https://pubmed.ncbi.nlm.nih.gov/22609376/
4. Xie G, et al. (2017). Eriodictyol attenuates arsenic trioxide-induced liver injury by activation of Nrf2. Oncotarget. https://pubmed.ncbi.nlm.nih.gov/28978146/
5. Lv P, et al. (2019). Eriodictyol inhibits high glucose-induced oxidative stress and inflammation in retinal ganglial cells. Journal of Cellular Biochemistry. https://pubmed.ncbi.nlm.nih.gov/30317656/
6. Yoo JM, et al. (2012). Inhibitory effect of eriodictyol on IgE/Ag-induced type I hypersensitivity. Bioscience, Biotechnology, and Biochemistry. https://pubmed.ncbi.nlm.nih.gov/22785465/
7. Guo P, et al. (2022). Eriodictyol and homoeriodictyol improve memory impairment in Aβ(25–35)-induced mice by inhibiting the NLRP3 inflammasome. Molecules. https://pubmed.ncbi.nlm.nih.gov/35458684/
8. Mariyappan P, et al. (2017). Effect of eriodictyol on preneoplastic lesions, oxidative stress and bacterial enzymes in 1,2-dimethylhydrazine-induced colon carcinogenesis. Toxicology Research. https://pubmed.ncbi.nlm.nih.gov/30090535/
9. Ley JP, et al. (2005). Evaluation of bitter-masking flavanones from Herba Santa (Eriodictyon californicum). Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/16028996/
10. Liu YL, et al. (1992). Isolation of potential cancer-chemopreventive agents from Eriodictyon californicum. Journal of Natural Products. https://pubmed.ncbi.nlm.nih.gov/1593282/
11. Yáñez JA, et al. (2008). Pharmacokinetics of selected chiral flavonoids: hesperetin, naringenin and eriodictyol in rats and their content in fruit juices. Biopharmaceutics & Drug Disposition. https://pubmed.ncbi.nlm.nih.gov/18058792/
12. Shock CC, et al. (2026). Chemical composition of Eriodictyon californicum (California yerba santa) cultivated in Ontario, Oregon, USA. Molecules. https://pubmed.ncbi.nlm.nih.gov/42076034/
13. Pereira ACH, et al. (2017). Gastroprotective activity of the resin from Virola oleifera. Pharmaceutical Biology. https://pubmed.ncbi.nlm.nih.gov/27937036/

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