Banisteriopsis caapi is a vine found in tropical South America. It is best known for being a main ingredient in ayahuasca, an entheogenic brew that is used by shamans of the region's indigenous tribes. B. caapi contains several different psychoactive alkaloids, most notably the mao inhibitors harmine, harmaline, and tetrahydroharmine. Ayahuasca can be made with a variety of different plants, but all formulas contain some DMT (N,N-dimethyltryptamine)-producing plant. The purpose of the B. caapi in the brew is to render the DMT orally active.