Pau d’arco is cooling, biter, alterative, antibiotic, antifungal, antitumor, antiviral, antineoplastic, digestive, diuretic, fungicidal, antidiabetic, anodyne, analgesic, astringent, parasiticide and hypotensive. Its constituents are lapachol, a quinone and a recognized antitumor agent found in the wood and barely in the bark. According to H. Wagner, head of the Institute of Pharmaceutical Biology at the University of Munich in Germany, much of the basis for pau d’arco’s reputation is its immune-stimulating properties. Quinones are present throughout nature. They are involved in the transference of hydrogen and electrons.
Lapachol, found in the inner bark, activates human immune cells (lymphocytes and granulocytes) in low concentrations. Lymphocytes include cells that mediate immunological reactions, such as T-cells. Granulocytes are white blood cells found in the blood that devour foreign cells and bacteria. Lapachol is barely soluble in water.