Tetrahydroharmine

Tetrahydroharmine (THH) is a fluorescent indole alkaloid and β-carboline that occurs in the tropical liana species Banisteriopsis caapi.

Effects

THH has been reported to produce psychoactive effects similar to those of harmaline in humans. It has been reported to be about one-third as potent as harmaline at a dose of 300mg orally. THH is believed to be one of the constituents of Banisteriopsis caapi responsible for the hallucinogenic effects of the plant.

Pharmacology

THH, like other harmala alkaloids in B. caapi, namely harmaline and harmine, is a reversible inhibitor of monoamine oxidase A (RIMA), but it also inhibits the reuptake of serotonin. THH contributes to B. caapi's psychoactivity as a serotonin reuptake inhibitor. In contrast to other β-carbolines, THH shows minimal affinity for the serotonin 5-HT_2A receptor (K_i = >10,000nM for racemic THH and R(+)-THH, K_i = 5,890nM for S(–)-THH). Similarly, THH shows negligible affinity for the serotonin 5-HT_1A and 5-HT_2C receptors and the dopamine D₂ receptor.

Society and culture

Legal status

Australia

Harmala alkaloids are considered Schedule 9 prohibited substances under the Poisons Standard (October 2015). A Schedule 9 substance is a substance which may be abused or misused, the manufacture, possession, sale or use of which should be prohibited by law except when required for medical or scientific research, or for analytical, teaching or training purposes with approval of Commonwealth and/or State or Territory Health Authorities.

See also

• Substituted β-carboline
• Ayahuasca
• Coronaridine