Structural Biochemistry/Ayahuasca

Definition

Ayahuasca is a plant psychotropic used by the indigeneous of the Amazon basin in South America. The beverage holds a central position in shamanic ethnomedicine of the region. It is a powerful sacred hallucinogen which is made from the ayahuasca vine (Banisteriopsis caapi) and the leaf of the chacruna plant (Psychotria viridis). The vine Banisteriopsis caapi contains MAO inhibitors which render the psychoactive agent of Psychotria viridis, N,N-dimethyltryptamine (DMT), orally active. The name in itself suggests its properties, ayahuasca being Quechua for "the vine of the souls", implying a means for communion with the spirit of the universe itself.

Use and General Effects

Ayahuasca is primarily used as a medicine or tool of healing, which according to locals can cure anything. It is prepared by soaking and boiling the bark and stems of Banisteriopsis caapi together with the leaves of Psychotria viridis as well as any additional admixture plants (Brugmansia spp., Erythroxylum coca, or Nicotiana rustica). When the brew is consumed its primary effects are: a purge (vomiting) that cleanses and heals the body and mind, accompanied by visions as well as an altered consciousness that is said to allow the drinker to directly communicate with the deeper spiritual intelligence of the ayahuasca spirit. The time of onset is approximately 20 to 60 minutes after ingestion, and the effects last approximately 4 to 8 hours. Traditionally the brew would be consumed by a village healer, or curandero, who would use ayahuasca to diagnose and cure those that came to him (or her) of whatever mental, spiritual, or physical ailment that was bothering them.

Chemistry of Ayahuasca

The major alkaloids of Banisteriopsis caapi are the ß-carboline derivatives harmine, tetrahydroharmine, and harmaline. Harmine and harmaline are highly reversible monoamine oxidase (MAO) inhibitors, while tetrahydroharmine is a weak serotonin (5-hydroxytryptamine) uptake inhibitor at presynaptic sites. Psychotria viridis on the other hand contains a single major alkaloid, N,N-dimethyltryptamine (DMT) as well as N-methyl tryptamine and methyl-tetrahydro-ß-carboline that have been reported as trace constituents. The principle action of ß-carbolines is their inhibition of peripheral MAO, which protects the DMT in the ayahuasca brew from peripheral degradation, rendering it orally active and allowing it to pass through the blood-brain barrier and activate receptor sites in the brain. In addition concentrations of serotonin increase in the body as both its reuptake and metabolism by MAO-A are blocked by ß-carbolines. ß-carbolines are highly selective inhibitors of MAO-A, which is the form of the enzyme for which the preferred substrates are tryptamines such as serotonin or DMT. Psychoactive alkaloids that are often present in ayahuasca when admixture plants such as Brugmansia spp. or Nicotiana rustica are added, also become potentiated by the ß-carboline inhibition of MAO enzymes.

The process that is inhibited is the MAO enzyme catalysis of oxidative deamination of biogenic monoamines. The oxidation occurs according to the general reaction equation: RCH₂NH₂ + O₂ + H₂O + MAO → RCHO + NH₃ + H₂O. The enzyme is widely distributed through various tissues in vertebrates and invertebrates such as the brain, liver, small intestine, heart, lungs, and blood plasma and platelets. The MAO system functions as a detoxifying mechanism to protect the nervous and cardiovascular systems from biogenic amines that could be toxic and be ingested through diet. These amines are generally formed as the result of aromatic amino acid decarboxylation.

Ayahuasca Analogues

Ayahuasca analogues are plants or chemicals that are used in place of the traditional constituents of the ayahuasca brew (Banisteriopsis caapi and Psychotria viridis). The analogues are meant to have a constituent that replaces the MAO inhibiting behavior of the ß-carbolines in Banisteriopsis caapi and a constituent that replaces the DMT in Psychotria viridis.

Examples of plant combinations that may achieve similar results to traditional ayahuasca can be found by using the following analogues:

DMT containing plants: Mimosa hostilis, Diplopterys cabrerana, Psychotria carthagenensis, Acacia maidenii, Anadenanthera peregrina

MAO inhibiting plants: Peganum harmala, Passiflora spp.

References

Callaway, J. C., D. J. McKenna, C. S. Grob, G. S. Brito, L. P. Raymon, R.E. Poland, E. N. Andrade, E. O. Andrade, D. C. Mash (1998) Pharmacology of Hoasca alkaloids in Healthy Humans. Journal of Ethnopharmacology. In Press.

Grunwell, J. N. “Ayahuasca Tourism In South America.” Newsletter of the Multidisciplinary Association for Psychedelic Studies (MAPS) 8.3 (Autumn 1998): 59-62.

Heaven, R., Charing, H.G. "Plant Spirit Shamanism." Destiny Books. Rochester, VT. 2006. 82-87.

McKenna, D., G. H. N. Towers, & F. S. Abbott. (1984) Monoamine oxidase inhibitors in South American hallucinogenic plants: Tryptamine and ß-carboline constituents of ayahausca. Journal of Ethnopharmacology 10:195-223.