Aucubin

Aucubin at a Glance

Aucubin is an iridoid glycoside — a C9 iridoid glucoside — and one of the most widely distributed iridoids in the plant kingdom. It takes its name from Aucuba japonica and recurs across the database as a marker of plantain, mullein leaf, Eucommia bark, rehmannia and chaste-tree fruit.

Its evidence is almost entirely preclinical but unusually coherent: a marquee hepatoprotective / anti-fibrotic signal sits on top of a shared antioxidant / anti-inflammatory mechanism (Nrf2 activation, NF-κB suppression) that also carries its neuroprotective, bone and kidney findings ^{1,3Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →Reference 3Shi X et al. · 2023Aucubin inhibits hepatic stellate cell activation through stimulating Nrf2/Smad7 axisView study →}.

Two disciplines are load-bearing. In chaste-tree, aucubin is a quality-control marker used to standardize the extract, not the tested agent — the same marker≠isolate rule as its co-marker agnuside. And aucubin has low oral bioavailability while its aglycone aucubigenin is unstable and chemically reactive, so in-vitro potency overreads what an oral dose delivers ^{2,14Reference 2Suh NJ et al. · 1991Pharmacokinetic study of an iridoid glucoside: aucubinView study →Reference 14Kim DH et al. · 2000Mechanism of covalent adduct formation of aucubin to proteinsView study →}.

Aucubin as a Vitex (Chaste-Tree) Marker

The single most important framing for aucubin’s clinical footprint is that it is a standardization marker for chaste-tree (Vitex agnus-castus), not a drug tested in its own right. The one controlled human study in which aucubin appears is a Vitex PCOS RCT (60 women, 12 weeks) in which the extract was standardized to aucubin content — delivering only ~0.42–0.82 mg aucubin/day as a quality-control quantity ^{11Reference 11Hatami A et al. · 2026RCTThe effect of Vitex agnus-castus on markers of oxidative stress, lipid profile and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind controlled clinical trialView study →}. The tested agent, and any effect, belong to the whole extract’s dopaminergic/hormonal fraction, which Vitex pharmacology attributes to its diterpenes rather than its iridoids ^{13Reference 13Wuttke W et al. · 2003Chaste tree (Vitex agnus-castus) — pharmacology and clinical indicationsView study →}.

Aucubin co-occurs in chaste-tree fruit with agnuside, the other iridoid used to quantify and standardize these extracts — so a label reading “standardized to aucubin/agnuside” is a statement about extract identity and batch consistency, not evidence that either isolated iridoid produces the clinical effect. Read aucubin’s own dossier as an organ-protection story (below); its appearance in a Vitex trial says nothing about the isolate.

Iridoid Instability & Aucubigenin

Aucubin’s chemistry is central to both its pharmacokinetics and its safety. As a glucoside it is water-soluble and reasonably stable in the intact molecule, but two reactions define its real-world behaviour:

• Acid degradation. Aucubin is unstable in gastric fluid — a degradation half-life of ~5 h at pH 1.2 — which, alongside low lipophilicity and first-pass metabolism, is why oral bioavailability is low (~19% in rats) ^{2Reference 2Suh NJ et al. · 1991Pharmacokinetic study of an iridoid glucoside: aucubinView study →}.
• Aglycone release. Gut and tissue β-glucosidase cleaves the sugar to liberate the aglycone aucubigenin, which is unstable and chemically reactive: it forms covalent protein adducts in vitro via an imine intermediate (intact aucubin itself did not bind) ^{14Reference 14Kim DH et al. · 2000Mechanism of covalent adduct formation of aucubin to proteinsView study →}.

The practical consequence is a short-lived, poorly-absorbed glycoside whose reactive aglycone is the mechanistic basis for treating high-dose or aglycone exposure cautiously — and the reason isolate potency in cell and high-dose parenteral studies does not transfer cleanly to an achievable oral human exposure.

What It's Used For

Aucubin’s profile is preclinical but internally consistent: one antioxidant/anti-inflammatory core (Nrf2, NF-κB) that surfaces as organ protection in liver, brain, bone and kidney models. The load-bearing caveat is the compound-page discipline — no human isolate data, and the reactive, poorly-absorbed chemistry above limits translation.

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 isolate data, so scores stay modest by design.

01Hepatoprotective / anti-fibroticPromising46%CCl₄-fibrosis Nrf2/Smad7 + liver I/R + review ^{1,3,4Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →Reference 3Shi X et al. · 2023Aucubin inhibits hepatic stellate cell activation through stimulating Nrf2/Smad7 axisView study →Reference 4Zhang S et al. · 2020Aucubin attenuates liver ischemia-reperfusion injury by inhibiting the HMGB1/TLR-4/NF-κB signaling pathway, oxidative stress, and apoptosisView study →}

02Anti-inflammatory / antioxidantShaky40%Cross-cutting Nrf2/HO-1 + NF-κB/NLRP3 mechanism ^{1,5Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →Reference 5Chaitanya MVNL et al. · 2025Deciphering the iridoids’ boundaries: from soil ecology to anti-inflammatory medicinesView study →}

03NeuroprotectiveShaky32%MPTP Parkinson + cerebral I/R rodent models ^{6,7Reference 6Zhu YL et al. · 2018AnimalAucubin alleviates glial cell activation and preserves dopaminergic neurons in MPTP-induced parkinsonian miceView study →Reference 7Liang Y et al. · 2024Neuroprotective effects of aucubin against cerebral ischemia-reperfusion injuryView study →}

04Anti-osteoporoticShaky30%Osteoblast differentiation + OVX preosteoclast/angiogenesis ^{8,9Reference 8Li Y et al. · 2020Aucubin exerts anti-osteoporotic effects by promoting osteoblast differentiationView study →Reference 9Li Z et al. · 2022AnimalAucubin impeded preosteoclast fusion and enhanced CD31ʰⁱEMCNʰⁱ vessel angiogenesis in ovariectomized miceView study →}

05RenoprotectiveShaky22%One diabetic-kidney-disease autophagy study ^{10Reference 10Wang H et al. · 2025Aucubin ameliorates diabetic kidney disease by restoring hGENCs autophagy through promoting phosphorylation of ATG4B proteinView study →}

Mechanisms

The load-bearing, reproduced finding is the Nrf2-anchored antioxidant/anti-fibrotic core; the organ-specific labels (neuro, bone, kidney) are largely single- or double-study extensions of that same mechanism.

Pharmacokinetics

Aucubin is a typical poorly-absorbed iridoid glucoside. The classic rat study reports oral bioavailability ~19.3% (100 mg/kg) with a short postdistributive half-life (~42.5 min i.v.), attributing the low oral figure to acid instability in gastric fluid (degradation half-life ~5 h at pH 1.2), low lipophilicity and GI/hepatic first-pass metabolism ^{2Reference 2Suh NJ et al. · 1991Pharmacokinetic study of an iridoid glucoside: aucubinView study →}. The review adds wide tissue distribution (kidney, liver, heart, spleen, lung) and a reported sex difference in absorption ^{1Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →}. The aglycone chemistry — β-glucosidase liberating reactive aucubigenin ^{14Reference 14Kim DH et al. · 2000Mechanism of covalent adduct formation of aucubin to proteinsView study →} — is covered under Iridoid Instability & Aucubigenin above; net, a short-lived, poorly-absorbed glycoside whose in-vitro and high-dose parenteral potency outruns what an oral dose plausibly delivers.

Clinical Trials

There are no trials of isolated aucubin. The one controlled human study in which aucubin appears is the Vitex agnus-castus PCOS RCT (60 women, 12 weeks), where the extract was standardized to aucubin content (~0.42–0.82 mg/day) as a quality-control marker — the tested agent, and any effect, belong to the whole extract’s dopaminergic/hormonal fraction, not to aucubin ^{11Reference 11Hatami A et al. · 2026RCTThe effect of Vitex agnus-castus on markers of oxidative stress, lipid profile and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind controlled clinical trialView study →}.

Last checked: July 2026.

Isolate vs. Plant Studies

The split is unusually clean and cuts both ways. The organ-protection literature — liver fibrosis and ischemia-reperfusion, MPTP and cerebral-ischemia neuroprotection, osteoblast/osteoclast and diabetic-kidney models — is almost all done with the isolated compound in rodents and cell lines ^{3,4,6,7,8,9,10Reference 3Shi X et al. · 2023Aucubin inhibits hepatic stellate cell activation through stimulating Nrf2/Smad7 axisView study →Reference 4Zhang S et al. · 2020Aucubin attenuates liver ischemia-reperfusion injury by inhibiting the HMGB1/TLR-4/NF-κB signaling pathway, oxidative stress, and apoptosisView study →Reference 6Zhu YL et al. · 2018AnimalAucubin alleviates glial cell activation and preserves dopaminergic neurons in MPTP-induced parkinsonian miceView study →Reference 7Liang Y et al. · 2024Neuroprotective effects of aucubin against cerebral ischemia-reperfusion injuryView study →Reference 8Li Y et al. · 2020Aucubin exerts anti-osteoporotic effects by promoting osteoblast differentiationView study →Reference 9Li Z et al. · 2022AnimalAucubin impeded preosteoclast fusion and enhanced CD31ʰⁱEMCNʰⁱ vessel angiogenesis in ovariectomized miceView study →Reference 10Wang H et al. · 2025Aucubin ameliorates diabetic kidney disease by restoring hGENCs autophagy through promoting phosphorylation of ATG4B proteinView study →}, which is a genuine strength: those are aucubin’s own effects, not a plant extract’s. The weakness is translational, not attributional — poor oral bioavailability and the reactive aglycone ^{2,14Reference 2Suh NJ et al. · 1991Pharmacokinetic study of an iridoid glucoside: aucubinView study →Reference 14Kim DH et al. · 2000Mechanism of covalent adduct formation of aucubin to proteinsView study →} mean isolate potency doesn’t transfer cleanly to an oral human dose. The hormonal / gynaecological context is the opposite: in the chaste-tree PCOS RCT aucubin is only a standardization marker; the extract, not the molecule, was tested, and the reproductive-hormone activity of Vitex is attributed to its dopaminergic diterpenes, not its iridoids ^{11,13Reference 11Hatami A et al. · 2026RCTThe effect of Vitex agnus-castus on markers of oxidative stress, lipid profile and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind controlled clinical trialView study →Reference 13Wuttke W et al. · 2003Chaste tree (Vitex agnus-castus) — pharmacology and clinical indicationsView study →}. Read aucubin’s own dossier as the antioxidant/anti-fibrotic organ-protection story; its appearance in a Vitex trial says nothing about the isolate.

Its Role in Plants

In the plant, aucubin is a defensive iridoid. Iridoid glycosides are bitter, deterrent compounds whose ecological function is chemical defence: stored inert as the glucoside, they are activated when tissue damage brings the molecule into contact with β-glucosidase, releasing the reactive aucubigenin aglycone that deters and can harm herbivores and pathogens — the same enzyme-triggered activation that underlies its pharmacokinetics ^{5,14Reference 5Chaitanya MVNL et al. · 2025Deciphering the iridoids’ boundaries: from soil ecology to anti-inflammatory medicinesView study →Reference 14Kim DH et al. · 2000Mechanism of covalent adduct formation of aucubin to proteinsView study →}. This is why aucubin recurs across chemically-defended Lamiales lineages (plantains, mullein, louseworts) and is used as a chemotaxonomic marker for them.

As with any constituent, a compound’s defensive role in the plant is plant biology, not human pharmacology, and does not predict what it does as a medicine.

Prevalence in Nature

Aucubin is one of the most widely distributed iridoid glycosides in flowering plants, concentrated in the order Lamiales and neighbours. It is the namesake constituent of spotted laurel (Aucuba japonica, Garryaceae), and a recurring marker across plantains (Plantago spp., Plantaginaceae), mullein (Verbascum thapsus) — where it is a leaf iridoid ^{12Reference 12Turker AU · 2005Common mullein (Verbascum thapsus L.): recent advances in researchView study →} — Eucommia ulmoides bark (du zhong, a rich source used in several of the organ studies), Rehmannia glutinosa, the lousewort genus Pedicularis (where it is a diagnostic iridoid), and chaste-tree (Vitex agnus-castus) fruit, in which it co-occurs with agnuside as a QC marker ^{11Reference 11Hatami A et al. · 2026RCTThe effect of Vitex agnus-castus on markers of oxidative stress, lipid profile and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind controlled clinical trialView study →}. Biosynthetically it belongs to the iridoid pathway (geraniol → 8-oxogeranial → iridodial via iridoid synthase, then oxidation and glucosylation to the iridoid glucoside). Absolute content is rarely quantified as % dry weight and varies widely with species, plant part (often leaf/bark) and provenance, so no reliable cross-source concentration ranking exists — a gap tracked for a later pass rather than asserted here.

Discovery & Synthesis

Aucubin was first isolated from Aucuba japonica (spotted laurel), from which it takes its name — an early entry in the long 19th–20th-century effort to characterise the bitter iridoid glucosides of Lamiales; its structure as a C9 iridoid glucoside was settled by mid-20th-century natural-product chemistry (older synonyms aucuboside and rhinanthin survive from that period). Total synthesis of the aucubin skeleton has been pursued in the iridoid-synthesis literature, but it is not the manufacturing route: supply for research is by extraction from aucubin-rich plants (notably Eucommia ulmoides bark and Plantago and Aucuba leaf), because the molecule is abundant in nature and its reactive aglycone makes synthesis unattractive versus isolation.

Patents: not yet researched.

Toxicity & Safety

Aucubin reads as a low-toxicity, food-and-medicine-adjacent iridoid — the pharmacology/toxicology review characterises its toxicity as low ^{1Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →} — but two honest, chemistry-driven caveats keep the rating off “none,” and no isolate toxicology package exists.

Safety at a Glance

✅ Low / no toxicity

• A widespread dietary/medicinal plant iridoid. Present in plantain, mullein and other long-used herbs with no acute toxicity signal at the doses used in rodent studies ^{1Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →}.
• Real-world marker exposure is tiny. As a chaste-tree standardization marker, incidental intake is well under ~1 mg/day ^{11Reference 11Hatami A et al. · 2026RCTThe effect of Vitex agnus-castus on markers of oxidative stress, lipid profile and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind controlled clinical trialView study →}.
• The aglycone is reactive. β-glucosidase liberates aucubigenin, which forms covalent protein adducts in vitro — a chemistry caveat, though intact aucubin itself did not bind ^{14Reference 14Kim DH et al. · 2000Mechanism of covalent adduct formation of aucubin to proteinsView study →}.
• No comprehensive isolate toxicology. No definitive LD50, genotoxicity or repeat-dose organ-toxicity package for the pure compound; reproductive safety of the isolate is not established ^{1Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →}.

Full Safety & Interactions Detail

Aucubin carries a low flag. It is a natural iridoid glycoside of foods-and-medicines with a long dietary/decoction history, and rodent efficacy studies report no acute toxicity signal at the doses used; the dedicated review characterises its toxicity profile as low ^{1Reference 1Zeng X et al. · 2020ReviewA review of the pharmacology and toxicology of aucubinView study →}.

The caveats are chemical and evidentiary rather than observed harms. First, the aglycone aucubigenin — released when gut β-glucosidase cleaves the sugar — is unstable and reactive and forms covalent protein adducts in vitro (via an imine intermediate; intact aucubin did not bind), which is the mechanistic basis for treating high-dose or aglycone exposure cautiously ^{14Reference 14Kim DH et al. · 2000Mechanism of covalent adduct formation of aucubin to proteinsView study →}.

Second, there is no comprehensive isolate toxicology (no definitive LD50, genotoxicity or repeat-dose package) and no reproductive-safety data for pure aucubin. Any pregnancy/lactation caution around aucubin-containing herbs (e.g. hormonally-active Vitex agnus-castus) belongs to the source herb and its actives, not to the iridoid marker — that decision lives on the herb page, not here. Poor oral bioavailability further limits real-world isolate exposure ^{2Reference 2Suh NJ et al. · 1991Pharmacokinetic study of an iridoid glucoside: aucubinView study →}.

Dosage

There is no established or recommended human dose for isolated aucubin — it has never been given to people as an isolate for therapy. Cited figures are preclinical rodent research doses (µM in vitro; low-to-mid mg/kg in vivo, often dosed parenterally to bypass poor oral absorption), not recommendations, and they do not translate given ~19% oral bioavailability and a short half-life ^{2Reference 2Suh NJ et al. · 1991Pharmacokinetic study of an iridoid glucoside: aucubinView study →}. Human exposure occurs incidentally through whole plants (plantain, mullein leaf, Eucommia, Rehmannia). In the chaste-tree PCOS trial the standardized extract supplied only ~0.42–0.82 mg aucubin/day — a quality-control marker quantity, not a therapeutic aucubin dose ^{11Reference 11Hatami A et al. · 2026RCTThe effect of Vitex agnus-castus on markers of oxidative stress, lipid profile and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind controlled clinical trialView study →}. These are doses studied in research and are not a personal recommendation.

References

1. Zeng X, Guo F, Ouyang D. (2020). A review of the pharmacology and toxicology of aucubin. Fitoterapia. https://pubmed.ncbi.nlm.nih.gov/31790767/
2. Suh NJ, Shim CK, Lee MH, Kim SK, Chang IM. (1991). Pharmacokinetic study of an iridoid glucoside: aucubin. Pharmaceutical Research. https://pubmed.ncbi.nlm.nih.gov/1924160/
3. Shi X, et al. (2023). Aucubin inhibits hepatic stellate cell activation through stimulating Nrf2/Smad7 axis. European Journal of Pharmacology. https://pubmed.ncbi.nlm.nih.gov/37607604/
4. Zhang S, et al. (2020). Aucubin attenuates liver ischemia-reperfusion injury by inhibiting the HMGB1/TLR-4/NF-κB signaling pathway, oxidative stress, and apoptosis. Frontiers in Pharmacology. https://pubmed.ncbi.nlm.nih.gov/33013386/
5. Chaitanya MVNL, et al. (2025). Deciphering the iridoids’ boundaries: from soil ecology to anti-inflammatory medicines. Inflammopharmacology. https://pubmed.ncbi.nlm.nih.gov/40794373/
6. Zhu YL, et al. (2018). Aucubin alleviates glial cell activation and preserves dopaminergic neurons in MPTP-induced parkinsonian mice. Neuroreport. https://pubmed.ncbi.nlm.nih.gov/29985188/
7. Liang Y, et al. (2024). Neuroprotective effects of aucubin against cerebral ischemia-reperfusion injury. International Immunopharmacology. https://pubmed.ncbi.nlm.nih.gov/38335656/
8. Li Y, et al. (2020). Aucubin exerts anti-osteoporotic effects by promoting osteoblast differentiation. Aging (Albany NY). https://pubmed.ncbi.nlm.nih.gov/32023550/
9. Li Z, et al. (2022). Aucubin impeded preosteoclast fusion and enhanced CD31ʰⁱEMCNʰⁱ vessel angiogenesis in ovariectomized mice. Stem Cells International. https://pubmed.ncbi.nlm.nih.gov/36406003/
10. Wang H, et al. (2025). Aucubin ameliorates diabetic kidney disease by restoring hGENCs autophagy through promoting phosphorylation of ATG4B protein. Renal Failure. https://pubmed.ncbi.nlm.nih.gov/41536046/
11. Hatami A, et al. (2026). The effect of Vitex agnus-castus on markers of oxidative stress, lipid profile and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind controlled clinical trial. JBRA Assisted Reproduction. https://pubmed.ncbi.nlm.nih.gov/41428718/
12. Turker AU, Gurel E. (2005). Common mullein (Verbascum thapsus L.): recent advances in research. Phytotherapy Research. https://pubmed.ncbi.nlm.nih.gov/16222647/
13. Wuttke W, et al. (2003). Chaste tree (Vitex agnus-castus) — pharmacology and clinical indications. Phytomedicine. https://pubmed.ncbi.nlm.nih.gov/12809367/
14. Kim DH, Kim BR, Kim JY, et al. (2000). Mechanism of covalent adduct formation of aucubin to proteins. Toxicol Lett. https://pubmed.ncbi.nlm.nih.gov/10713483/

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