Source Naturals Pau D'Arco is the highest quality inner bark of the purple lapacho tree found in Brazil and Northern Argentina. Ever since ancient times, when it was a standard for the medicine men of the Inca Empire, pau d'arco also known as ipe roxo and taheebo has been one of the most widely-used herbs in South America. Its popularity is attributed to the active constituent, lapachol, which has been the subject of numerous scientific studies. This saturated extract is more than 3 times as potent as common tinctures.