tetrahydroharmine

Tetrahydroharmine (THH) is a beta-carboline alkaloid, the tetrahydro analog of harmine. It is produced in certain plants, most notably Banisteriopsis caapi, a key ingredient in the traditional entheogenic brew ayahuasca. THH commonly occurs in ayahuasca alongside harmine and harmaline, contributing to the pharmacological profile of the mixture.

Chemistry and occurrence: THH is formed by hydrogenation of harmine, resulting in a partially saturated bicyclic core. Its levels vary widely among plant strains and preparations; in some Banisteriopsis caapi varieties it is a prominent constituent, while in others it is present only in trace amounts.

Pharmacology: THH acts as a reversible inhibitor of monoamine oxidase A (MAO-A), a property shared with other beta-carbolines. It is generally less potent as an MAO-A inhibitor than harmine or harmaline, but it can contribute to the MAOI activity of ayahuasca. Preclinical studies have also explored potential antidepressant-like effects in animals, though data are limited.

Safety and regulation: Like other MAOI-containing preparations, THH can interact with serotonergic or sympathomimetic drugs and with tyramine-rich foods, potentially causing hypertensive events or serotonin syndrome. Regulatory status varies by country; THH is not widely scheduled on its own, but ayahuasca-containing products are regulated or prohibited in many jurisdictions.

Research and uses: THH is mainly of interest as part of ayahuasca pharmacology and as a potential pharmacological tool for studying MAO-A inhibition. There is limited clinical data on THH itself, and it is not approved as a therapeutic agent.