Pau D'Arco

This is now the herb’s best-supported activity, and unusually it reaches human cells. A bark extract of T. impetiginosa reduced pro-inflammatory cytokine output in primary human lymphocytes ex vivo, with some fractions outperforming a clinical positive control and no measured toxicity ^{3Reference 3Ryan et al. · 2021The medicinal plant Tabebuia impetiginosa potently reduces pro-inflammatory cytokine responses in primary human lymphocytes — ex vivo human cell studyView study →}; a separate Handroanthus impetiginosus extract cut pro-inflammatory cytokines and NF-κB nuclear translocation in the human THP-1 monocyte line ^{4Reference 4Rossi et al. · 2024In vitroEffects of Handroanthus impetiginosus (Mart. ex DC.) Mattos extract on inflammatory, immune, atherogenic profile and differentiation in the THP-1 human cell line — in vitroView study →}. Taheebo polyphenols selectively inhibit COX-2 (sparing COX-1) in murine and human macrophages, an effect traced to acteoside ^{10Reference 10Ma et al. · 2017In vitroTaheebo polyphenols attenuate free fatty acid-induced inflammation in murine and human macrophage cell lines as inhibitor of cyclooxygenase-2 — in vitroView study →}, and the isolated quinone beta-lapachone suppresses inducible nitric oxide synthase (iNOS), cytokines and matrix metalloproteinases in activated microglia ^{11,21Reference 11Mokarizadeh et al. · 2020ReviewAn evaluation on potential anti-inflammatory effects of β-lapachone — reviewView study →Reference 21Lee et al. · 2015In vitroLee, E. J., Ko, H. M., Jeong, Y. H., Park, E. M., & Kim, H. S. (2015). β-Lapachone suppresses neuroinflammation by modulating the expression of cytokines and matrix metalloproteinases in activated microglia — in vitro. Journal of Neuroinflammation, 12, 133. https://pubmed.ncbi.nlm.nih.gov/26173397/View study →}. In animals, a Tabebuia ethanol extract eased monoiodoacetate-induced osteoarthritis in rats via NF-κB/AP-1 suppression and chondroprotection ^{5Reference 5Park et al. · 2017In vitroTabetri (Tabebuia avellanedae ethanol extract) ameliorates osteoarthritis symptoms induced by monoiodoacetate through anti-inflammatory and chondroprotective activities — rat model and in vitroView study →}, and oral taheebo water extract prevented DSS colitis in mice by shifting T-helper responses ^{22Reference 22Park et al. · 2017AnimalOral administration of taheebo (Tabebuia avellanedae) water extract prevents DSS-induced colitis in mice — animal modelView study →}. A 12-week randomised double-blind placebo-controlled osteoarthritis trial of the same extract (n=100) has completed but its results are not yet published ^{6Reference 6Nutribiotech Co · 2017RCTEfficacy and safety of Tabetri (Tabebuia avellanedae ethanol extract) on osteoarthritis — 12-week multicenter randomised double-blind placebo-controlled trial (n=100), completed; results not yet publishedView study →}.

Gap: the human evidence is ex vivo cell work plus one registered-but-unpublished RCT — no peer-reviewed human clinical outcome for the whole herb yet.

The anticancer reputation is real in the lab but concentrated in one molecule. A 2025 systematic review found the genus’s antiproliferative activity dominated by beta-lapachone, which kills tumour cells selectively through the two-electron reductase NQO1 (highly expressed in many solid tumours) and inhibits IDO1 and topoisomerase ^{2,15Reference 2Mosquera-Morales et al. · 2025Systematic reviewIn vitro antiproliferative activity in plants of the genus Tabebuia: A systematic reviewView study →Reference 15Flick et al. · 2013In vitroThe tumor-selective cytotoxic agent β-lapachone is a potent inhibitor of IDO1 — in vitroView study →}. β-Lapachone shows apoptosis and anti-metastatic effects in colorectal cancer cells and mice ^{23Reference 23Kee et al. · 2017In vitroKee, J. Y., Han, Y. H., Park, J., et al. (2017). β-Lapachone inhibits lung metastasis of colorectal cancer by inducing apoptosis of CT26 cells — in vitro and mouse model. Integrative Cancer Therapies, 16(4), 585-596. https://pubmed.ncbi.nlm.nih.gov/27923905/View study →}, anti-aromatase activity in a post-menopausal breast-cancer cell model ^{24Reference 24Telang et al. · 2019In vitroGrowth inhibitory efficacy and anti-aromatase activity of Tabebuia avellanedae in a post-menopausal Luminal A breast cancer model — in vitroView study →}, and broad cytotoxicity in vitro — but the same in vitro work flags genotoxicity (DNA damage, micronuclei), a reminder these are cytotoxic quinones ^{25Reference 25Lima et al. · 2024In vitroAnticancer potential and safety profile of β-lapachone in vitro — genotoxicity assessedView study →}. Crucially, human trials have used the synthetic analogue ARQ 761, not pau d’arco: a phase 1 study in refractory solid tumours found only modest single-agent activity (best response stable disease) with dose-limiting anaemia and methaemoglobinaemia ^{8Reference 8Gerber et al. · 2018Clinical trialPhase 1 study of ARQ 761, a β-lapachone analogue that promotes NQO1-mediated programmed cancer cell necrosis — clinical trialView study →}. Whole-herb evidence is thinner and mixed — a mouse azoxymethane colon-carcinogenesis study found no protective effect from Tabebuia-derived β-lapachone ^{26Reference 26Higa et al. · 2011AnimalStudy of the antineoplastic action of Tabebuia avellanedae in azoxymethane-induced carcinogenesis in mice — animal model (null result)View study →} — and lapachol itself is a vitamin-K antagonist that can promote metastasis at high doses ^{27Reference 27Maeda et al. · 2008AnimalPromotion or suppression of experimental metastasis of B16 melanoma cells after oral administration of lapachol — mouse model; vitamin K antagonismView study →}.

Gap: the compelling data are for a purified synthetic quinone at controlled intravenous doses; there is no evidence the tea or bark extract delivers a meaningful anticancer dose safely.

Two independent rat studies give this a consistent preclinical footing. An ethanolic bark extract of T. avellanedae protected against ethanol- and ibuprofen-induced gastric lesions, boosted gastric mucus, and reduced acid secretion and H+/K+-ATPase activity ^{16Reference 16Twardowschy et al. · 2008AnimalAntiulcerogenic activity of bark extract of Tabebuia avellanedae — rat modelView study →}; a follow-up showed the same extract accelerated healing of established acetic-acid ulcers by increasing mucus and gastric-mucosa cell proliferation ^{28Reference 28Pereira et al. · 2013AnimalAntiulcer effect of bark extract of Tabebuia avellanedae: activation of cell proliferation in gastric mucosa during healing — rat modelView study →}. Polysaccharide fractions from related Handroanthus leaves add a separate gastroprotective mechanism (mucus and glutathione preservation) ^{29Reference 29Silva et al. · 2009In vitroEvaluation of the antifungal potential of Brazilian Cerrado medicinal plants — in vitroView study →}.

Gap: entirely rodent; no human dosing, and the effective preparations were concentrated ethanol extracts rather than a traditional decoction.

Broad-spectrum antibacterial action is well replicated in vitro and attributed to the bark’s naphthoquinones and anthraquinones. Genus extracts inhibit Staphylococcus aureus (including MRSA), Helicobacter pylori, Brucella and Bacillus subtilis, but not E. coli ^{12,30Reference 12Jiménez-González et al. · 2013ReviewAnti-infectious activity in plants of the genus Tabebuia — reviewView study →Reference 30Machado et al. · 2003In vitroIn vitro activity of Brazilian medicinal plants, naturally occurring naphthoquinones and their analogues, against methicillin-resistant Staphylococcus aureus — in vitroView study →}. Against H. pylori, taheebo-derived 2-(hydroxymethyl)anthraquinone was more active than metronidazole in MIC assays ^{13Reference 13Park et al. · 2006In vitroAntibacterial activity of Tabebuia impetiginosa Martius ex DC (Taheebo) against Helicobacter pylori — in vitroView study →}, and structure-activity work on furanonaphthoquinone derivatives confirms the quinone scaffold drives the activity ^{31Reference 31Yamashita et al. · 2021In vitroStructure-activity relationship studies of antimicrobial naphthoquinones derived from constituents of Tabebuia avellanedae — in vitroView study →}.

Gap: all in vitro; no clinical or even in vivo infection-model data, and activity depends on quinone content that is frequently low in commercial bark.

Antifungal activity underpins the herb’s most popular folk use (candidiasis), and the in vitro evidence is consistent. Tabebuia extracts inhibit Candida albicans and multiple non-albicans Candida species, plus Cryptococcus, Aspergillus and dermatophytes such as Trichophyton and Microsporum ^{14,29,32Reference 14Portillo et al. · 2001In vitroAntifungal activity of Paraguayan plants used in traditional medicine — in vitroView study →Reference 29Silva et al. · 2009In vitroEvaluation of the antifungal potential of Brazilian Cerrado medicinal plants — in vitroView study →Reference 32Höfling et al. · 2010In vitroAntimicrobial potential of some plant extracts against Candida species — in vitroView study →}. The activity tracks with lapachol and beta-lapachone, thought to act by uncoupling oxidative phosphorylation and disrupting fungal respiration ^{12Reference 12Jiménez-González et al. · 2013ReviewAnti-infectious activity in plants of the genus Tabebuia — reviewView study →}.

Gap: no human trials for candidiasis despite widespread use; effect requires adequate quinone extraction, which a simple tea may not achieve.

Rodent antinociception is replicated across models. An aqueous inner-bark extract of T. avellanedae reduced acetic-acid writhing and formalin-phase-two pain in mice, an effect linked to the adenosine (not opioid) system ^{33Reference 33de Miranda et al. · 2001AnimalAntinociceptive and antiedematogenic properties and acute toxicity of Tabebuia avellanedae inner bark aqueous extract — mouse and rat modelView study →}, and an ethanolic taheebo extract raised pain thresholds and reduced paw edema in several models ^{34Reference 34Lee et al. · 2012AnimalAnalgesic and anti-inflammatory effects in animal models of an ethanolic extract of taheebo, the inner bark of Tabebuia avellanedae — animal modelView study →}. In humans, the open-label dysmenorrhea trial reported a significant fall in pain intensity from baseline, but with no placebo arm this cannot be separated from expectation effects ^{7Reference 7McClure et al. · 2022Safety and tolerability of Pau d’Arco (Tabebuia avellanedae) for primary dysmenorrhea: a single-arm, open-label trial (n=12)View study →}.

Gap: the only human analgesic signal is uncontrolled; controlled trials are needed before the effect is credible in people.

Traditional antimalarial and antiparasitic use has partial preclinical backing. Against Giardia duodenalis in an organoid-derived human intestinal model, T. avellanedae extract and beta-lapachone were active, with β-lapachone showing a lower IC50 than metronidazole and the hydroalcoholic extract sparing host cells ^{35Reference 35Rigamonti et al. · 2025In vitroSelective activity of Tabebuia avellanedae against Giardia duodenalis infecting organoid-derived human gastrointestinal epithelia — in vitroView study →}. Lapachol has weak antimalarial activity but stronger action against Trypanosoma cruzi and Leishmania ^{12Reference 12Jiménez-González et al. · 2013ReviewAnti-infectious activity in plants of the genus Tabebuia — reviewView study →}.

Gap: all in vitro; the whole-herb effect is modest relative to the isolated quinone, and no in vivo or human antiparasitic data exist.

Two mouse studies from one Brazilian group give a coherent but narrow signal. An ethanolic bark extract produced antidepressant-like effects in the forced-swim and tail-suspension tests, dependent on the monoaminergic system ^{17Reference 17Freitas et al. · 2010AnimalAntidepressant-like action of the ethanolic extract from Tabebuia avellanedae in mice: evidence for involvement of the monoaminergic system — animal modelView study →}, with a follow-up implicating NMDA-receptor blockade and the L-arginine–nitric oxide–cGMP pathway ^{36Reference 36Freitas et al. · 2013AnimalNMDA receptors and the L-arginine-nitric oxide-cyclic GMP pathway are implicated in the antidepressant-like action of the ethanolic extract from Tabebuia avellanedae in mice — animal modelView study →}; the bark phenolic caffeic acid is proposed as an active constituent.

Gap: single-laboratory rodent behavioural models only; no clinical data, and the doses/extract are not standardised to a marker.

Antioxidant activity is well demonstrated at the constituent level but not in people. Phenylpropanoid glycosides isolated from the water extract show strong DPPH radical scavenging (one with an IC50 near 0.12 µM) ^{18Reference 18Suo et al. · 2013In vitroBioactive phenylpropanoid glycosides from Tabebuia avellanedae — in vitro antioxidant and CYP3A4 inhibitionView study →}, and specioside plus an inner-bark n-butanol fraction from a related Tabebuia activate the Keap1-Nrf2 pathway, inducing HMOX-1/NQO1 and protecting liver cells from oxidative stress ^{37Reference 37Garzón-Castaño et al. · 2020In vitroActivation of the Keap1-Nrf2 pathway by specioside and the n-butanol extract from the inner bark of Tabebuia rosea — in vitroView study →}.

Gap: in vitro and cell-based only; the antioxidant claim is inferred from isolated fractions, with no whole-herb human biomarker data.

A metabolic signal comes mainly from β-lapachone and taheebo extracts in rodents. Beta-lapachone prevented weight gain in high-fat-diet and genetically obese mice by driving brown-adipose thermogenesis (UCP1) via AMPK ^{19Reference 19Kwak et al. · 2019In vitroKwak, H. J., Jeong, M. Y., Um, J. Y., & Park, J. (2019). β-Lapachone regulates obesity through modulating thermogenesis in brown adipose tissue and adipocytes via AMPK signaling — mouse model and in vitro. American Journal of Chinese Medicine, 47(4), 803-822. https://pubmed.ncbi.nlm.nih.gov/31094212/View study →}, and an n-butanol taheebo fraction reduced body weight and fat mass in ovariectomised mice ^{38Reference 38Iwamoto et al. · 2016AnimalThe anti-obesity effect of taheebo (Tabebuia avellanedae) extract in ovariectomized mice — animal modelView study →}.

Gap: animal and isolated-compound work only; human metabolic trials exist for the synthetic β-lapachone analogue MB12066, not for pau d’arco.

Exploratory rat models suggest CNS activity consistent with traditional “tonic” use. A leaf ethyl-acetate fraction improved memory and reduced oxidative and inflammatory markers in a cyclophosphamide chemobrain model ^{20Reference 20Khaled et al. · 2024AnimalLC-qTOF-MS/MS phytochemical profiling of Tabebuia impetiginosa leaf and assessment of its neuroprotective potential in rats — animal modelView study →}, and a bark aqueous extract raised brain dopamine and reduced catalepsy in chemically induced parkinsonism ^{39Reference 39Pal Roy et al. · 2022AnimalAntiparkinsonian activity of Tabebuia impetiginosa bark and biochemical analysis of dopamine in rat brain homogenates — animal modelView study →}.

Gap: isolated single-model rodent studies, partly on the leaf rather than the medicinal bark; far from clinical relevance.

Pau d’arco is generally well tolerated: an aqueous bark extract showed low acute toxicity in rodents ^{33Reference 33de Miranda et al. · 2001AnimalAntinociceptive and antiedematogenic properties and acute toxicity of Tabebuia avellanedae inner bark aqueous extract — mouse and rat modelView study →}, bark extracts were non-toxic to primary human immune cells ^{3Reference 3Ryan et al. · 2021The medicinal plant Tabebuia impetiginosa potently reduces pro-inflammatory cytokine responses in primary human lymphocytes — ex vivo human cell studyView study →}, and an 8-week open-label human trial of 1,050 mg/day encapsulated bark reported only mild adverse events with laboratory markers largely within normal limits ^{7Reference 7McClure et al. · 2022Safety and tolerability of Pau d’Arco (Tabebuia avellanedae) for primary dysmenorrhea: a single-arm, open-label trial (n=12)View study →}. The main pharmacological concern is the marker naphthoquinone lapachol, a vitamin-K antagonist: at high doses in animals it prolongs a hypercoagulable, warfarin-like state, so pau d’arco should be used cautiously with anticoagulants, antiplatelet drugs, and around surgery, and avoided in bleeding disorders ^{27Reference 27Maeda et al. · 2008AnimalPromotion or suppression of experimental metastasis of B16 melanoma cells after oral administration of lapachol — mouse model; vitamin K antagonismView study →}. Phenylpropanoid glycosides from the bark moderately inhibit CYP3A4 in vitro, a theoretical basis for interactions with CYP3A4-metabolised drugs ^{18Reference 18Suo et al. · 2013In vitroBioactive phenylpropanoid glycosides from Tabebuia avellanedae — in vitro antioxidant and CYP3A4 inhibitionView study →}. High doses of decoction (more than ~250 mL at once) have reportedly caused nausea and diarrhoea; note that the intravenous β-lapachone drug analogue causes anaemia and methaemoglobinaemia at pharmacological doses, but these have not been reported from the herb itself ^{8Reference 8Gerber et al. · 2018Clinical trialPhase 1 study of ARQ 761, a β-lapachone analogue that promotes NQO1-mediated programmed cancer cell necrosis — clinical trialView study →}.

The “moderate” toxicity flag reflects this split: whole-herb bark extracts show low acute and ex-vivo toxicity, whereas the isolated quinones are genotoxic in vitro and lapachol carries a real vitamin-K-antagonist / bleeding concern — so the herb warrants more caution than a benign food, even though the bark itself is well tolerated at customary doses.