Traditional Uses of Pau D'Arco

+ South America

Indications of Tabebuia use, imply it has been used since before the incas. As with many of the Amazonian herbs, tribes from all over the rainforest with little or no connection with each other have used this herb for much the same purposes and preparations for hundreds of years [7].

The wood of Tabebuia has been used for centuries to make strong bows for hunting [7].

Pau D'Arco has been used in throughout South America for conditions such as ulcers, syphilis, urinary tract infections, gastrointestinal infections, candidiasis, cancer, diabetes, prostatitis, constipation, rheumatism, arthritis, dysentery, stomatitis, boils, and allergies [7].

Colombians have reportedly used a bark infusion as a CNS stimulant, and a decoction by the Bahamians was employed for a similar reason as an energizing tonic to give strength [1].

In Brazil, T. avellanedae bark infusion is used to treat malaria, cancer, fever, stomach disorders, bacterial and fungal infections, and to relieve a variety of mental, and emotional states (anxiety, poor memory, irritability, and depression) [1].

Herb Details: Pau D'Arco

Botanical Information

Pau D'arco is a massive tree found in the Amazon rainforest, as well as other parts of tropical South and Central America. This tree grows to heights of about 30 meters with a base diameter of about 1.5-3 meters.

There are two species of pau D'arco used as medicine — Tabebuia impetiginosa and Tabebuia avellanedae. The Tabebuia genus contains about 100 species and is a popular decorative plant, especially in its native South America. The flowers of this genus are vibrant and long-lived.

The Tabebuia genus is known for its beautiful, vibrant flowers, and is often used in landscaping in South American cities and homes. Various species of Tabebuia produce different colored flowers. As a genus, Tabebuia contains about 100 species [4, 7]. The wood is also often used, providing heavy, durable, high-quality timber for anything from construction, to tools [7].

Much of the Tabebuia on the market today are considered a by-product of the lumber industry, which accounts for some of the confusion and contradiction in the medicinal use of this plant. As it arrives at the lumber mill, many of the distinguishing features showing which species of Tabebuia it is, are missing at this point and is considered just "Pau D'arco " [7].

Unfortunately, it has also been reported that the mahogany shavings found on the floors of the lumber mills (which produce a similar texture, odor, and color to true Tabebuia impetiginosa/avellanedae) are often swept up and packaged as Pau D'arco as well. This is evident after a study conducting chemical analysis of 12 commercially available Pau D'arco products, found only one of those products actually contained lapachol, which itself was in trace amounts compared to the documented concentration of 2-7% in true Pau D'arco [7].

Habitat, Ecology, Distribution

The Tabebuia genus is found throughout the Amazon rainforest as well as other parts of South America [7]). This genus has a strong presence in the highly diverse and vibrant canopy of the Amazon rainforest.

Harvesting, Collection, & Preparation

Tabebuia is harvested from the rainforest as lumber and sent off to processing factories to be cut up into useable pieces.

It's here that Tabebuia is identified as "Pau D'arco " (despite substantial differences in constituent levels between various Tabebuia species), and the inner bark is stripped off and sold on the herbal market. The heartwood is then cut into timber and used for various uses.

The fact has been well documented through laboratory analysis that the heartwood contains the highest concentrations of lapachol, and this is what most of the scientific research has focused on [7] — thus a conflict is born. Good quality Pau D'arco (Tabebuia impetiginosa) will contain about 4% lapachol.

The quinoids contained within Tabebuia are not very water soluble and must be boiled for at least. 10-15 minutes to be extracted in any sort of therapeutic amount [7]. Therefore a simple infusion will not extract the constituents that are most sought after.

To best use Pau D'Arco, a decoction, or hydroalcoholic extract is best.

Pharmacology & Medical Research

Much of the early research on Tabebuia was fuelled by its reported anti-cancer qualities throughout the 1960s [7]. Some of these studies showing evidence that Tabebuia provided a positive effect against Tumors, eventually drew the attention of the National Cancer Institute (NCI), which in turn backed more research in this area [7].

The issue, however, was that the NCI was testing single plant extracts (such as lapachol), rather than the whole plant extract, and reported that they were unable to produce therapeutic effects without side effects and discontinued research shortly afterward. As Taylor L, (2005) points out, the side effects (nausea, vomiting, and anti-vitamin K activity) are very similar to current chemotherapy medication side effects. She also points out that there have been other chemicals discovered in Tabebuia that produce positive effects on vitamin K, and may, in fact, neutralize the adverse effects lapachol may have on vitamin K activity.

+ Antibacterial

Tabebuia spp. (T. ochracea, T. rosea, T. impetiginosa, T. avellanedae) has clearly demonstrated broad-spectrum actions against several disease-causing microorganisms including bacteria such as various strains of Staphylococcus aureus, Helicobacter pylori, Brucella, and Bacillus subtilis. These effects are suggested to be through the various naphthoquinones contained in the bark. [4].

Various leaf extracts (from T. rosea, T. chrysantha) were also shown to inhibit bacteria such as Staphylococcus aureus, Klebsiella pneumoniae, these results were associated with its phenolic constituents [4].

No extract of Tabebuia spp. was found to produce practical antibacterial effects against E. coli [4].

+ Cancer

Some (National Cancer Institute) NCI funded studies in the late 1960s looking into lapachols effects on cancer, reported that they were unable to produce therapeutic effects without such side effects as nausea, vomiting, and anti-vitamin K activity (vitamin K is necessary for bone health, among other things). These effects are similar to side effects noted in modern chemotherapy. What the NCI failed to realize is that by testing lapachol by itself, it was missing some of the possible synergistic chemicals also found within Tabebuia, some of which provide positive effects on vitamin K activity. These chemicals may be the reason some other studies looking at the whole plant extract have reported little or no side effects, while also providing evidence for significant anti-cancer properties. Nevertheless, lapachol has been found to produce anticancer effects in vivo, and in vitro.

Taylor L. (2005) refers to a study done in 1980 on lapachols effect on 9 human patients with various cancers (liver, kidney, breast, prostate, cervix). This study reported that pure lapachol was able to shrink tumors and reduce pain caused by them, with 3 of these patients attaining complete remission.

Other quinones contained in Tabebuia including beta-lapachone were reported to provide significant anticancer activity as well [7]. Beta-lapachone was reported to provide support for cancers such as promyelocytic leukemia, prostate, malignant glioma, colon, hepatoma, breast, ovarian, pancreatic, multiple myeloma cell lines, and drug-resistant cell lines [7]. The mechanism of action from this constituent has been suggested to be inhibition of IDO1 (this means it works best on cancer cell lines that rely on this enzyme to stay intact) [5].

N.C de Sousa et al., (2009), reports that the naphthoquinones found in T. avellanedae showed potent cytotoxicity against several cancer cell lines and lower toxicity against certain normal human cell lines than the drug mitomycin. The synthetic version of beta-lapachone has shown similar results but with more side effects.

+ Depression

A. E. Freitas et al., (2013) determined that the caffeic acid contained in T. avellanedae produced both antioxidant effects and antidepressant effects. These effects on depressive states were noted to be through the modulation of NMDA (N-methyl- D-aspartate) receptors.

+ Antifungal

Pau D'arco (Tabebuia spp.) has provided clear evidence in vitro against fungi such as Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Saccharomyces cerevisiae, Cryptococcus neoformans, Microsporum gypseum, Penicillium purpurogenum and Trichophyton mentagrophytes [4].

Candida albicans is a commensal microorganism in the human digestive, and vaginal cavities. It can become an opportunistic pathogen [22], resulting in candidiasis.

The tabebuia genus of plants are commonly used in traditional medicine for the treatment of various infections. This genus of plants contains high concentrations of quinones [14], furanonaphthoquinones [13], and naphthoquinones [15]. The main compounds shown to be responsible for the antifungal activity in Tabebuia species includes lapachol and beta-lapachone [19].

Several members of the Tabebuia genus have been shown to have antimicrobial activity against many different cell cultures in vitro. T. avellanedae, T. impetiginosa have the most research behind them, with T. caraiba featured in a few studies. Tabebuia spp. extracts containing naphthoquinones, quinones, and anthraquinones were shown to have broad antimicrobial activity against Staphylococcus aureus, Helicobacter pylori, Aspergillus fumigatus, Candida spp., Cryptococcus neoformans, Microsporum gypseum, Penicillium purpurogenum, Saccharomyces cerevisiae and Trichophyton mentagrophytes [9, 10, 11, 12]

In vitro studies investigating the specific inhibitory activity of known antifungal plant species including Tabebuia avellanedae found to inhibit Candida albicans, Candida dubliniensis, Candida parapsilosis, Candida tropicalis, Candida guilliermondii, Candida utilis, Candida krusei, Candida lusitaniae, Candida glabrata and Candida rugosa [18].

The mechanism of action for these effects is reported to be through an uncoupling oxidative phosphorylation and inhibition of cell respiratory mechanisms through an interaction with the cells membrane directly. This suggestion is backed up further by an in vitro study that found a large number of naphthoquinones had direct inhibitory activity on the electron transport chain in bacterial and fungal cell cultures [17].

+ Antinflammatory

Beta-lapachone has been shown to produce anti-inflammatory effects, through modulation of various inflammatory molecules (inhibition of inducible nitric oxide synthase, cytokine expressions, and MMPs), and multiple signaling pathways, and has been suggested as a preventative therapeutic agent in disease associated with neuroinflammation [2].

+ Antinociceptive

T. avellanedae aqueous extract was found to possess antinociceptive, as well as anti-edematogenic effects in rats and the mechanism of action was associated with the adenosine system [3]. These results validate some of its traditional uses such as analgesic, and anti-inflammatory applications.

+ Antioxidant

6 phenylpropanoid glycosides were discovered in the aqueous extract of T. avellanedae, and these were suggested to provide strong antioxidant, as well as moderate inhibition of CYP3A4 enzyme [6].

+ Antiparasitic

Pau D'arco has demonstrated an activity against such parasites as malaria, schistosoma, trypanosoma [7].

Lapachol has been noted to produce low activity against Plasmodium berghei in mice and Plasmodium falciparum in vitro, and a higher activity against parasites such as Trypanosoma cruzi and Leishmania infantum [4].

+ Psoriasis

Due to the activity contained in Tabebuia, against the growth of human keratinocytes, Tabebuia is suggested to provide antipsoriatic effects [7].

+ Antiviral

Various constituents contained within tabebuia have demonstrated properties in vitro against viruses including herpes I and II, influenza, poliovirus, and vesicular stomatitis virus [7]. Other studies have noted a lack of research in this area, with a few studies showing minor to no antiviral activity [4].

+ Contraindications

• Pregnancy or lactation
• Caution advised with high doses

Synergy With other herbs & Nutrients

The anticancer effects of lapachone are noted to be through noncompetitive inhibition of IDO1 [5], among other mechanisms, and likely have synergy in this action with other botanicals. More research is needed, however.

Other constituents are noted to combat some of the adverse side effects resulting from chemotherapy such as vitamin K support. These effects need to be explored further to understand how this may be used to combat the adverse side effects felt with chemotherapy.

For candida pau d'arco is often combined with other anti-fungal herbs such as oregano, black walnut, myrrh, goldenseal or other berberine-containing herbs.