Lapacho Bark (Pau d'Arco)

A South American bark rarely seen on UK labels — heritage, chemistry and honest caution

All articles checked for accuracy against the GB NHC Register and all sources have citations with verified links to their relevant studies.

Lapacho, or Pau d'Arco, is the inner bark of a South and Central American trumpet tree. It’s chemically interesting and culturally significant, but its laboratory potency does not equate to proven benefits in people.

This article explains what lapacho bark is, where it comes from, which compounds draw scientific attention, and why the human clinical evidence is limited. It also sets out how WellsparQ uses a small amount of the bark, and why careful sourcing and safety caution matter.

Ingredient Snapshot

What it is

The inner bark of a South American trumpet-tree, used as a botanical ingredient.

Where from

Handroanthus (formerly Tabebuia) species — South and Central America

Known for

Noted for naphthoquinones such as lapachol and β‑lapachone; chiefly studied in laboratory research.

In WellsparQ

• GutHerb Plus15 mg

Lapacho — better known by its Portuguese name Pau d'Arco, "bow stick" — is the inner bark of a tall flowering tree of South and Central America. It is an unusual sight on a British supplement label, and WellsparQ includes it in one formula as a small, declared botanical. This piece leans into what the bark actually is: its tree, its long regional history, its distinctive chemistry, and the honest limits of the evidence.

The tree behind the bark

Pau d'Arco comes from trees of the trumpet-tree family (Bignoniaceae), famous across the tropics for their blaze of pink or yellow blossom. The species most associated with medicinal lapacho is _Handroanthus impetiginosus_ (long known as Tabebuia impetiginosa or T. avellanedae) — the genus was reorganised, so older sources use Tabebuia and newer ones Handroanthus ^¹. The wood is famously dense and rot-resistant; indigenous peoples used it for hunting bows, and the inner bark was brewed into a traditional decoction. That heritage use is a matter of cultural history, recorded as such — not evidence of a health benefit.

What makes the chemistry distinctive

Lapacho's interest to chemists lies in a family of pigmented compounds called naphthoquinones. The two most cited are lapachol and β-lapachone ^¹²³. β-Lapachone in particular has been studied intensively in the laboratory, and its structure has been used as a starting point for chemical modification in drug-discovery research ^².

What the research does — and does not — show

Here honesty matters most. The published work on lapacho and its constituents is overwhelmingly preclinical — cells and animals, not people. A 2025 systematic review in Molecules gathered the in-vitro antiproliferative studies across the genus Tabebuia and mapped which extracts and compounds had been examined in the laboratory ^¹. A 2022 systematic review in Toxicon looked at the anticancer research on Handroanthus and, importantly, its toxicity, underlining that these naphthoquinones are biologically potent and not without hazard ^³. And a 2021 review in the European Journal of Medicinal Chemistry surveyed the mechanisms and drug-development interest around β-lapachone specifically ^².

The consistent message from these reviews is twofold: the chemistry is genuinely interesting, and the human clinical evidence is lacking. None of this establishes that consuming lapacho bark produces a health benefit in people, and we do not suggest it does.

How WellsparQ uses it

Source: WellsparQ Supplements Database. At 15 mg it is a small, characterful botanical within a wider herbal formula — included for its heritage and place in the blend, declared by weight rather than buried. The formula is plant-based and suitable for vegetarians and vegans.

Sourcing and suitability

Genuine lapacho is the inner bark, and quality varies: material sold as Pau d'Arco has historically been variable in botanical identity and in naphthoquinone content, which is one reason careful sourcing and identity testing matter. As a bark powder it is inherently vegan and vegetarian.

Safety — a section worth reading

Because lapacho's naphthoquinones are potent, caution is genuinely warranted, and saying so is part of the brand's honesty standard. Lapachol has recognised toxicity at higher intakes in animal studies, and the toxicity literature is explicit that these compounds are not benign in quantity ^³. Traditional decoctions used far larger amounts of bark than a 15 mg supplement addition. Pregnant and breastfeeding women should avoid lapacho; it is also not appropriate for anyone on anticoagulant medication without medical advice, given reported effects on blood clotting in the older literature. Anyone taking medication or managing a health condition should check with a GP or pharmacist first, and keep strictly to the stated amount.