Tetrahydroharmine (THH) is a

fluorescent Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

indole alkaloid Indole alkaloids are a class of alkaloids containing a structural moiety of indole; many indole alkaloids also include isoprene groups and are thus called terpene indole or secologanin tryptamine alkaloids. Containing more than 4100 known differ ...

and β-carboline that occurs in the tropical

liana A liana is a long-Plant stem, stemmed Woody plant, woody vine that is rooted in the soil at ground level and uses trees, as well as other means of vertical support, to climb up to the Canopy (biology), canopy in search of direct sunlight. T ...

species ''

Banisteriopsis caapi ''Banisteriopsis caapi'', also known as, caapi, soul vine, yagé (yage), or ayahuasca (the latter of which also refers to the psychedelic decoction made with the vine and a plant source of dimethyltryptamine) is a South American liana of the fam ...

''.

Effects

THH has been reported to produce

psychoactive A psychoactive drug, psychopharmaceutical, mind-altering drug, consciousness-altering drug, psychoactive substance, or psychotropic substance is a chemical substance that alters psychological functioning by modulating central nervous system acti ...

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 ''

'' responsible for the

hallucinogen Hallucinogens, also known as psychedelics, entheogens, or historically as psychotomimetics, are a large and diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mo ...

ic effects of the plant.

Pharmacology

THH, like other

harmala alkaloid Harmala alkaloids are several alkaloids that act as monoamine oxidase inhibitors (MAOIs). These alkaloids are found in the seeds of ''Peganum harmala'' (also known as harmal or Syrian rue), as well as ''Banisteriopsis caapi'' (ayahuasca), leave ...

s in ''B. caapi'', namely harmaline and harmine, is a reversible inhibitor of monoamine oxidase A (RIMA), but it also inhibits the

reuptake Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal (i.e., the pre-synaptic neuron at a synapse) or glial cell after it has performed its function of transmi ...

serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...

. THH contributes to ''B. caapi'''s psychoactivity as a

serotonin reuptake inhibitor A serotonin reuptake inhibitor (SRI) is a type of drug which acts as a reuptake inhibitor of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) by blocking the drug action, action of the serotonin transporter (SERT). This in turn lea ...

. In contrast to other β-carbolines, THH shows minimal

affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Pa ...

for the serotonin 5-HT_2A receptor (K_i = >10,000nM for

racemic In chemistry, a racemic mixture or racemate () is a mixture that has equal amounts (50:50) of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as r ...

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 Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...

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.

Effects

Pharmacology

Society and culture

Legal status

Australia

See also

References

Further reading