From the Amazonian rain forest comes one of the most potent catalysts for expanded awareness yet discovered by human beings.
In Ecuador and Peru this medicine is known as Ayahuasca, a Quechua Indian word most prevalent meaning,  “vine of the Soul”. (Also sometimes: “vine of the dead”)
In Columbia and parts of Brazil, the Tupi Indian name Yage (pronounced Ya-hay) is used, and among Amazonia’s proliferating mestizo relious cults it is called Daime…

“Ayahuasca” as an entheogenic substance does not properly refer to one single plant, but to a singular mixture of two very different plant species…
there is no such thing as an “Ayahuasca plant,” or a “yage plant”.
Ayahuasca correctly refers to a psychedelic combination of plants which varies in potency according to the skill of its maker.

While each shaman has his own secret formula for the mixture (with probably no two exactly alike), it has been established that true ayahuasca always contains both beta-carboline and tryptamine alkaloids, the former (harmine and harmaline) usually obtained from the Banisteriopsis caapi vine, and the latter (N, N-dimethyl-tryptamine, or DMT) from the leaves of the Psychotria viridis bush.
Peganum Harmala can also be used as a MAO inhibitor.
Mimosa Hostilis (Jurema), Acacia Confusa (Rainbow Tree) or Diplopterys Cabrerana (Chaliponga) can be used for the DMT.
There may be variations among plant species, but the alkaloids are always consistent.

It is significant to note that neither one of these plant substances by itself is normally psychoactive in oral doses.
(Harmine/harmaline is said to effect hallucinosis at highly toxic levels, but in less heroic quantities it is at best a tranquilizer, at worst an emetic.)
DMT, in any quantity, is not orally active unless used in combination with a monoamine oxidase (MAO) inhibitor.
This principle is precisely what makes Ayahuasca effective;
the harmala alkaloids in the MAOI are potent short term MAO inhibitors which synergize with the DMT-containing plants to produce what has been described as one of the most profound of all entheogenic experiences.

Ayahuasca effects, experience and benefits