DMT is a component of ayahuasca, not the same thing. Ayahuasca combines a DMT-containing plant (Psychotria viridis) with the Banisteriopsis caapi vine, which contains MAOI beta-carbolines. DMT alone is destroyed by gut monoamine oxidase before it can reach the brain. The MAOIs in the vine disable that enzyme, making the DMT orally active. Without the vine, no psychoactive effect occurs. Ayahuasca is the whole system; DMT is one component of it.