Pau d'Arco and Cancer: Exploring the Research & Evidence

For decades, the inner bark of the Pau d'Arco tree (Tabebuia impetiginosa) has been a subject of scientific scrutiny. Often referred to as the "divine tree" by South American indigenous cultures, its traditional use spans centuries. In the mid-20th century, that traditional use caught the attention of oncology researchers — and it's been studied, in different forms, ever since.

This article separates what's actually been studied from what's just repeated online. Every finding below is tagged by evidence type, because "researchers are studying X" and "X treats cancer in people" are very different claims, and conflating them is exactly what makes health content on the internet untrustworthy.

The Power of Lapachol and Beta-Lapachone

The primary interest in Pau d'Arco's studied antitumor activity centers on two naphthoquinones: lapachol and beta-lapachone. Both were isolated in the 1960s and became the focus of early National Cancer Institute (NCI) research.

Research attention later shifted to beta-lapachone, which lab studies describe as more selective for cancer cells while leaving healthy cells relatively untouched. According to a review in Molecules, beta-lapachone interacts with an enzyme called NQO1, which is often overexpressed in several human cancers, including breast, lung, and colorectal types — in laboratory cell models.

Apoptosis: Programmed Cell Death, in Cell Lines

One heavily studied mechanism is beta-lapachone's ability to trigger apoptosis (programmed cell death) in cancer cell lines grown in a lab — cells naturally "self-destruct" when damaged, and cancer cells often bypass that process.

Metastasis and Angiogenesis Signaling, in Lab Models

Beyond cell death, some research has looked at whether Pau d'Arco compounds affect the AKT1/mTOR signaling pathway — a pathway that's often hyperactive in cancer and tied to both tumor growth and the chronic inflammation covered in our Pau d'Arco and Inflammation article.

Modern Clinical Research: ARQ 761

Much of the early lapachol research was set aside because of the isolated compound's side effects. More recently, a synthetic beta-lapachone analogue called ARQ 761 has entered clinical testing.

Whole Bark vs. Isolated Compounds

A recurring theme in herbal research is the difference between an isolated chemical compound and the whole plant as traditionally prepared.

Because the active naphthoquinones are not highly water-soluble, traditional preparation uses a decoction (simmered, not just steeped) to extract them effectively. If you're sourcing bark to prepare this way, our inner bark sourcing guide covers what to look for — we source our own reference-grade Pau d'Arco through Taheebo Wellness Tea.

How to Prepare a Pau d'Arco Decoction

1. Measure — 3 tablespoons of fine-grind Pau d'Arco inner bark per 4 cups of water.
2. Boil — in a stainless steel or glass pot (avoid aluminum).
3. Simmer — reduce heat and simmer at least 8–10 minutes; some traditional protocols go up to 20 minutes for a more concentrated brew.
4. Strain — through a fine mesh filter.
5. Serve — hot or cold.

For antimicrobial-related uses specifically, see our Pau d'Arco and Candida article — the underlying compounds overlap.

Precautions and Considerations

• Toxicity at high doses: isolated lapachol can cause nausea, vomiting, and dizziness in excess. Traditional preparation strengths are the relevant reference point, not concentrated isolate doses.
• Anticoagulant effects: Pau d'Arco may have blood-thinning properties and should not be combined with blood-thinning medication (e.g., Warfarin) or used before scheduled surgery without medical guidance.
• Pregnancy and breastfeeding: not recommended — some compounds have shown potential effects on fetal development in animal studies.
• Sourcing quality: many commercial products use outer bark or different species, which lack the same concentration of studied compounds as true inner bark.

Where This Leaves Us

The honest summary: Pau d'Arco's naphthoquinones have been studied repeatedly in cancer-cell and animal models, and one derivative (ARQ 761) has reached early-stage human clinical trials. None of that adds up to a treatment claim for drinking the tea — robust human clinical trials on Pau d'Arco tea itself, in cancer patients, don't yet exist. If you're evaluating Pau d'Arco alongside a cancer diagnosis, that decision belongs with your oncologist, not a wellness article. What the research supports today is scientific interest, not a substitute for medical care.

See our FAQ for sourcing and preparation questions, or the About & Methodology page for how we select and grade the research we cite.

References

1. 1.Molecules (2020): "Anticancer potential of resveratrol, β-lapachone and their analogues." PMC7070981.
2. 2.Journal of Ethnopharmacology: "Tabebuia impetiginosa: A comprehensive review on traditional uses, phytochemistry, and immunopharmacological properties."
3. 3.Nature / Scientific Reports: "Beta-lapachone selectively induces apoptosis in cancer cells via NQO1 activation."
4. 4.BMC Complementary Medicine and Therapies: "Antitumorous effects of Pau d'Arco inner bark extracts in human carcinoma cell lines."
5. 5.Clinical Cancer Research: "Phase I study of ARQ 761, a β-lapachone analogue, in patients with advanced solid tumors."