Pau d’arco comprises of a group of trees known to the botanist by the Latin name Tabebuia (tab-eb-u-ee-ah) and Tecoma. Pau d’arco are timber trees providing a high quality wood. They grow up to 150 feet with trunks to six feet in diameter. According to the world authority on the botany of Tabebuia, the late Alwyn H. Gentry (1945-1993), curator of the Missouri Botanical Garden in St. Louis, “Tabebuia have perhaps the hardest, heaviest, most durable wood of any neotropical tree. The cortex of pau d’arco ranges in color from a deep reddish brown or simple brown to a sandy pink, sometimes with sections of straw-like color and a charcoal gray. General appearance will vary in accord with the wood and with age, species, and ecological factors peculiar to the region of harvest. The inner barks of yellow-flowered pau d’arco show a straw-like color throughout.
Today Pau d’arco is one of the most widely used immunostimulating plants known. Until all the commotion caused by the media in Brazil, there were few studies on the activity of the bark, then suddenly the situation changed.
Earlier in this century in Brazil, Yale University foresters Samuel J. Record and Clayton D. Mell reported that they found numerous species of Tabeubia in the tropical American rain forests. The tree was accredited with “astringent” bark, valued as a treatment for syphilis. Record and Mell used local names to classify the different woods, giving pau d’arco to a group having wood of an “oily olive brown color” and vessels containing a yellow crystalline matter visible on the wood surface and appearing like sulfur. This crystalline matter in its pure form a bright, almost iridescent yellow is the biologically active plant pigment lapachol.
Brazilian scientists discovered that the bark of pau d’arco, one with tannish colored flowers with yellow throats contained a quinone with a wide spectrum of activity. They were encouraged by its action against the parasites that cause a tropical infection. Another team in Brazil found pain-relieving action from a wood extract of a yellow pau d’arco. They found lapachol was analgesic and one of the quinines they isolated was identical to the quinones previously found in the inner bark.
Studies of the leaves of pau d’arco has been few and far in between. There is some indication that the leaves may be more potent than the bark, and their harvest would be much less traumatic to the trees. As the mysteries of pau d’arco’s active constituents continue to unfold, we may take solace in the fact that once these are established, quality can be monitored to provide us with the best of barks.
