Most pau d'arco comes from a tree in the Amazon rain forest called Tabebuia avellanedae. It is a broad-leaf evergreen that grows to a height of 125 feet. The wood of this tree is so hard that it doesn't decay easily. Pau d'arco products are made from the inner bark of Tabebuia trees. The bark contains important chemical compounds called naphthoquinones.
Some naphthoquinones are beneficial for fighting infection and reducing inflammation.
But because most pau d'arco products are not standardized, they may or may not have a significant amount of the important active substances. Some herbal teas that are labeled pau d'arco aren't really made from Tabebuia trees. Always read the label to make sure that you're getting authentic pau d'arco. Look for Tabebuia avellanedae as an ingredient. Most of the chemical research on pau d'arco has been done on the wood and not the bark.