Pau D'Arco

Tabebuia bark has been used in South America since before the Incas. Tribes across the rainforest with little contact between them used the bark for much the same purposes ^{40Reference 40Taylor · 2005The Healing Power of Rainforest Herbs}.

Pau d’arco has been used throughout the continent for ulcers, syphilis, urinary-tract and gastrointestinal infections, candidiasis, cancer, diabetes, prostatitis, constipation, rheumatism, arthritis, dysentery and boils ^{40Reference 40Taylor · 2005The Healing Power of Rainforest Herbs}.

Colombian and Bahamian traditions used a bark infusion or decoction as a stimulating, strengthening tonic ^{1Reference 1Zhang et al. · 2020ReviewTabebuia impetiginosa: A comprehensive review on traditional uses, phytochemistry, and immunopharmacological properties — reviewView study →}. Across tropical America a bark infusion is also drunk for depression ^{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 →}.

In Brazil the bark tea of T. avellanedae is taken for malaria, fever, stomach disorders and infections, and to ease anxiety, poor memory and low mood ^{1Reference 1Zhang et al. · 2020ReviewTabebuia impetiginosa: A comprehensive review on traditional uses, phytochemistry, and immunopharmacological properties — reviewView study →}. Known there as ipê-roxo and pau d’arco, the tree is also used for inflammation, peptic ulcers, and bacterial and fungal infections ^{16,28Reference 16Twardowschy et al. · 2008AnimalAntiulcerogenic activity of bark extract of Tabebuia avellanedae — rat modelView study →Reference 28Pereira et al. · 2013AnimalAntiulcer effect of bark extract of Tabebuia avellanedae: activation of cell proliferation in gastric mucosa during healing — rat modelView study →}.

In northeastern Brazil the inner bark is used for pain and inflammation, for cancer and as a diuretic ^{33Reference 33de Miranda et al. · 2001AnimalAntinociceptive and antiedematogenic properties and acute toxicity of Tabebuia avellanedae inner bark aqueous extract — mouse and rat modelView study →}.

In Paraguay the bark is one of the plants used in traditional medicine for skin diseases ^{14Reference 14Portillo et al. · 2001In vitroAntifungal activity of Paraguayan plants used in traditional medicine — in vitroView study →}.

This is the herb’s best-supported activity, and it reaches human cells. Bark extracts of H. impetiginosus reduced pro-inflammatory cytokine output in primary human lymphocytes ex vivo, with some extracts outperforming a clinical positive control and none showing 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 H. 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, a water extract of the inner bark, selectively inhibit COX-2 (sparing COX-1) in 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 →}. Beta-lapachone suppresses 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 osteoarthritis in rats via NF-κB/AP-1 suppression ^{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 ^{22Reference 22Park et al. · 2017AnimalOral administration of taheebo (Tabebuia avellanedae) water extract prevents DSS-induced colitis in mice — animal modelView study →}.

A 12-week placebo-controlled osteoarthritis RCT of the same extract (n=100) has completed but is 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 research centres on one molecule. A 2025 systematic review found beta-lapachone to be the most evaluated antiproliferative compound in the genus ^{2Reference 2Mosquera-Morales et al. · 2025Systematic reviewIn vitro antiproliferative activity in plants of the genus Tabebuia: A systematic reviewView study →}. It kills tumour cells through the enzyme NQO1, which is highly expressed in many solid tumours, and inhibits the immune-regulating enzyme IDO1 ^{8,15Reference 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 →Reference 15Flick et al. · 2013In vitroThe tumor-selective cytotoxic agent β-lapachone is a potent inhibitor of IDO1 — in vitroView study →}.

β-Lapachone induced apoptosis in colorectal cancer cells and inhibited their spread to the lung in 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 →}. It was also genotoxic to the cancer cells it killed in vitro ^{25Reference 25Lima et al. · 2024In vitroAnticancer potential and safety profile of β-lapachone in vitro — genotoxicity assessedView study →}.

Finely ground inner bark inhibited the growth of an aromatase-expressing breast-cancer cell line and blocked aromatase activity ^{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 →}.

Human trials have used the synthetic analogue ARQ 761, not pau d’arco. In a phase 1 study of 42 patients with advanced solid tumours, it had modest single-agent activity, with anaemia as the dose-limiting toxicity and possible 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 →}.

In mice, β-lapachone extracted from T. avellanedae gave no protection against chemically induced colon lesions ^{26Reference 26Higa et al. · 2011AnimalStudy of the antineoplastic action of Tabebuia avellanedae in azoxymethane-induced carcinogenesis in mice — animal model (null result)View study →}. Lapachol given in a single high, toxic dose promoted the spread of melanoma cells in mice through vitamin K antagonism, while repeated low doses slightly suppressed it ^{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 anticancer 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 rat studies from the same Brazilian research group 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, at 100 and 300 mg/kg, reduced established acetic-acid ulcers by 44% and 36% 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 →}.

This is entirely rodent, with 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, Helicobacter pylori and Bacillus subtilis, but not E. coli ^{12Reference 12Jiménez-González et al. · 2013ReviewAnti-infectious activity in plants of the genus Tabebuia — reviewView study →}. Two naphthoquinones isolated from T. avellanedae were active against every S. aureus strain tested, including MRSA ^{30Reference 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, the inner-bark constituents 2-(hydroxymethyl)anthraquinone, anthraquinone-2-carboxylic acid and lapachol were 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 →}. Synthetic derivatives of its furanonaphthoquinones were active against bacteria, including MRSA, and fungi ^{31Reference 31Yamashita et al. · 2021In vitroStructure-activity relationship studies of antimicrobial naphthoquinones derived from constituents of Tabebuia avellanedae — in vitroView study →}.

All of it is in vitro, with no clinical or even in-vivo infection-model data, and the activity depends on quinone content that is frequently low in commercial bark.

Candidiasis is the herb’s most popular folk use, and the in vitro antifungal evidence is consistent. T. avellanedae extracts inhibit Candida species ^{32Reference 32Höfling et al. · 2010In vitroAntimicrobial potential of some plant extracts against Candida species — in vitroView study →} and were among the most active of 14 Paraguayan plants tested against a panel of 11 fungi ^{14Reference 14Portillo et al. · 2001In vitroAntifungal activity of Paraguayan plants used in traditional medicine — in vitroView study →}. An extract of the related T. caraiba was very active against the ringworm fungus Trichophyton rubrum ^{29Reference 29Silva et al. · 2009In vitroEvaluation of the antifungal potential of Brazilian Cerrado medicinal plants — 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, and the effect requires adequate quinone extraction that 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, and caffeine but not naloxone reversed the effect, pointing to the adenosine system rather than opioids ^{33Reference 33de Miranda et al. · 2001AnimalAntinociceptive and antiedematogenic properties and acute toxicity of Tabebuia avellanedae inner bark aqueous extract — mouse and rat modelView study →}. An ethanolic taheebo extract raised pain thresholds and reduced paw oedema 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 ^{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 →}. With no placebo arm, this cannot be separated from expectation effects.

Traditional antimalarial and antiparasitic use has partial preclinical backing. Against Giardia duodenalis, T. avellanedae extracts and beta-lapachone were all active, and β-lapachone had a lower IC50 than metronidazole ^{35Reference 35Rigamonti et al. · 2025In vitroSelective activity of Tabebuia avellanedae against Giardia duodenalis infecting organoid-derived human gastrointestinal epithelia — in vitroView study →}. Only the hydroalcoholic extract was free of toxicity to a human intestinal cell line ^{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 →}.

All of it is in vitro, 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 ^{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 →}.

These are single-laboratory rodent behavioral models only, with no clinical data and no marker-standardized dose.

Phenylpropanoid glycosides isolated from the water extract show strong DPPH radical scavenging, one with an IC50 of 0.12 µM ^{18Reference 18Suo et al. · 2013In vitroBioactive phenylpropanoid glycosides from Tabebuia avellanedae — in vitro antioxidant and CYP3A4 inhibitionView study →}. Specioside and an inner-bark n-butanol extract from the related Tabebuia rosea activate the Keap1-Nrf2 pathway, inducing HMOX-1 and 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 →}.

This is in-vitro and cell-based only, with no whole-herb human biomarker data.

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 →}. An n-butanol taheebo extract, fed for 16 weeks, reduced body weight and fat mass in ovariectomized mice ^{38Reference 38Iwamoto et al. · 2016AnimalThe anti-obesity effect of taheebo (Tabebuia avellanedae) extract in ovariectomized mice — animal modelView study →}.

This is animal and isolated-compound work only.

A leaf ethyl-acetate fraction improved memory and reduced oxidative and inflammatory markers in rats with cyclophosphamide-induced “chemobrain” ^{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 →}. An aqueous bark extract raised brain dopamine and reduced catalepsy in rat models of parkinsonism ^{39Reference 39Pal Roy et al. · 2022AnimalAntiparkinsonian activity of Tabebuia impetiginosa bark and biochemical analysis of dopamine in rat brain homogenates — animal modelView study →}.

These are single-model rodent studies, one of them on the leaf rather than the medicinal bark.

Tolerability. An aqueous inner-bark extract had low acute toxicity in mice ^{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 bark extracts were not 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 →}. In an 8-week open-label trial, 12 women took 1,050 mg/day of encapsulated bark. Nine reported an adverse event, most of them mild and none serious, and most laboratory markers stayed 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 →}.

Blood thinners. Lapachol is a vitamin K antagonist, the same mode of action as warfarin ^{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 →}. On that basis pau d’arco is used with care alongside anticoagulant and antiplatelet drugs and around surgery, and avoided in bleeding disorders.

CYP3A4. Phenylpropanoid glycosides from the bark moderately inhibit CYP3A4 in vitro, a possible basis for interactions with drugs metabolised by that enzyme ^{18Reference 18Suo et al. · 2013In vitroBioactive phenylpropanoid glycosides from Tabebuia avellanedae — in vitro antioxidant and CYP3A4 inhibitionView study →}.

High doses. Excessive use of the tea can cause nausea, vomiting, dizziness and diarrhoea ^{41Reference 41Fern · 2026Handroanthus impetiginosusView study →}.

Isolated quinones. β-Lapachone damages DNA in cells in vitro ^{25Reference 25Lima et al. · 2024In vitroAnticancer potential and safety profile of β-lapachone in vitro — genotoxicity assessedView study →}, and its intravenous drug analogue caused anaemia and possible methaemoglobinaemia at pharmacological doses ^{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 →}. These effects have not been reported from the bark itself.