Pau D’Arco (Tabebuia spp) was cited by a reader in a recent post. I had listed it in my post for herbs for treating CFS in 2015 but have not done a post focused on it. β-Lapachone (β-LAP) is a major part.
- “Tabebuia species have several uses in folk medicine, including their use to treat inflammation and rheumatism…showed significant antioxidant activity in the three evaluated assays….can be promising agents for the treatment for gouty arthritis, hyperuricemia, and inflammation. ” 
- In vitro antioxidant and free radical scavenging activity of different parts of Tabebuia pallida growing in Bangladesh .
- “The strong anti-inflammatory/anti-oxidant effects of β-LAP [a natural naphthoquinone compound isolated from the lapacho tree (Tabebuia sp.)] may provide preventive therapeutic potential for various neuroinflammatory disorders.” 
- “has been used in folk medicine as anti-inflammatory and in the treatment of ulcers, bacterial and fungal infections.” 
- Antibacterial activity of Tabebuia impetiginosa Martius ex DC (Taheebo) against Helicobacter pylori .
- “The present review focus in quinones found in species of Brazilian northeastern Capraria biflora, Lippia sidoides, Lippia microphylla and Tabebuia serratifolia.” 
- “These two isolates (dentified in the inner bark of taheebo, ) exhibited weak inhibition of Clostridium perfringens and Escherichia coli at 100 microg/disk while no adverse effects were observed on the growth of Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium infantis, Lactobacillus acidophilus, and Lactobacillus casei at 1000 microg/disk.” 
- “Tabebuia impetiginosa bark, Achyrocline sp. aerials parts, Larrea divaricata leaves, Rosa borboniana flowers, Punica granatum fruit pericarp, Psidium guineense fruit pericarp, Lithrea ternifolia leaves and Allium sativum bulbs produced some of the more active extracts.
- β-Lapachone activity in synergy with conventional antimicrobials against methicillin resistant Staphylococcus aureus strains . “Among the naphthoquinones, β-lapachone was the most effective against S. aureus strains…. This study demonstrated that, in general, β-lapachone combined with beta lactams antimicrobials, fluoroquinolones and carbapenems acts synergistically inhibiting MRSA strains.”
- ” Staphylococcus aureus strains were susceptible to extracts of Punica granatum and Tabebuia avellanedae…. demonstrated antibacterial activity against all S. aureus strains tested. ” 
- Activity of β-lapachone derivatives against rifampicin-susceptible and -resistant strains of Mycobacterium tuberculosis .
- Generation of superoxide anions and hydrogen peroxide from beta-lapachone in bacteria . i.e. more hydrogen peroxide is produced which inhibits many bacteria.
Pau D’Arco (Tabebuia spp) continues to be acceptable list for the following reasons:
- Does not inhibit Lactobacillus or Bifidobacterium.
- Minor effect against E.Coli
- Effective against S. aureus – which is implicated as being a significant bacteria with CFS (see this earlier post).
- Effective against Candida
Note: No PubMed studies with CFS/FM/IBS were found. There are many some forum posts indicating it helps with candida.
“Pau d’arco. While herbalists do use pau d’arco for CFS treatment, it hasn’t proven to be very effective. People on blood-thinner medications should not take pau d’arco.” [source]