Pau d'arco is a tree native to South America. Preparations derived from the bark have been traditionally used to treat bacterial, fungal, or viral infections, and cancer. Quinones have been identified as the main active constituents (1) (2) (3) (4).
In vitro and in vivo studies of compounds isolated from pau d'arco demonstrate antibacterial (5) (6) (7) (8), antifungal (9), antipsoriatic (10), immunomodulatory (11) (12), anti-inflammatory (13) (14), antidepressant (15), anticoagulant (16), anticancer (1) (2) (3) (4) (17), and antimetastatic (4) properties. Taheebo extract from the inner bark of pau d'arco selectively inhibits growth of ER positive breast cancer cells (18), but human studies are needed to validate these effects.
In a small single-arm study, the isolated naphthoquinone lapachol failed to show any effects on patients with non-leukemic tumors or chronic myelocytic leukemia (19).