Compound Monograph
Tetrahydroharmine
Tetrahydroharmine is a harmala alkaloid of Syrian rue and ayahuasca, structurally related to harmine and harmaline.
Classification
Tetrahydroharmine is a beta-carboline (harmala) alkaloid, part of the alkaloids class. Nitrogen-containing, often bitter and physiologically potent compounds — the group behind many of the strongest plant medicines and poisons.
Where Does It Come From? (2)
Tetrahydroharmine is a naturally occurring beta-carboline (harmala) alkaloid, found in Syrian rue and Ayahuasca vine. It is flagged as moderately toxic.
Research & Evidence
Tetrahydroharmine (THH) is one of the principal harmala alkaloids, occurring together with harmine and harmaline in Syrian rue and in the Banisteriopsis caapi vine used in ayahuasca. Alongside its weak monoamine oxidase inhibition, it is reported to have mild serotonin reuptake-inhibiting activity, and it is part of the alkaloid mixture that allows orally ingested DMT to become active in ayahuasca brews.
Monoamine oxidase (MAO) inhibition
Tetrahydroharmine (THH) is a weak MAO-A inhibitor relative to harmine and harmaline; within the ayahuasca alkaloid mixture its contribution is thought to lean more on serotonin-reuptake inhibition than on MAO inhibition, and no reliable standalone MAO potency value is established for it in isolation. See the natural MAO inhibitors guide for the better-quantified β-carbolines.
Toxicity & Safety
As a monoamine oxidase inhibitor, tetrahydroharmine carries the interaction risks common to MAOIs, including with tyramine-rich foods and serotonergic drugs. Its profile in isolation is not as well characterised as the broader ayahuasca context in which it is usually consumed.