|Other names||THH; 1,2,3,4-Tetrahydroharmine; Leptaflorine; 2,3,4,9-Tetrahydro-7-methoxy-1-methyl-1H-pyrido(3,4-b)indole|
|Chemical and physical data|
|Molar mass||216.284 g·mol−1|
|3D model (JSmol)|
Tetrahydroharmine (THH) is a fluorescent indole alkaloid that occurs in the tropical liana species Banisteriopsis caapi . 
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. 
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. 
Ayahuasca is a South American (pan-Amazonian) psychoactive brew used both socially and as ceremonial spiritual medicine among the indigenous peoples of the Amazon basin. It is growing in usage in Western society, including multiple Ayahuasca churches. It is a psychedelic and entheogenic mixed drink brew commonly made out of the Banisteriopsis caapi vine, the Psychotria viridis shrub or a substitute, and possibly other ingredients. A chemically similar preparation, sometimes called "pharmahuasca", can be prepared using N,N-Dimethyltryptamine (DMT) and a pharmaceutical monoamine oxidase inhibitor (MAOI), such as isocarboxazid. B. caapi contains several alkaloids that act as MAOIs, which are required for DMT to be orally active. Ayahuasca is prepared in a tea that, when consumed, causes an altered state of consciousness or "high", including visual hallucinations and altered perceptions of reality.
N,N-Dimethyltryptamine is a substituted tryptamine that occurs in many plants and animals, including human beings, and which is both a derivative and a structural analog of tryptamine. It is used as a recreational psychedelic drug and prepared by various cultures for ritual purposes as an entheogen.
Monoamine oxidase inhibitors (MAOIs) are a class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as highly efficacious anti-depressants, as well as effective therapeutic agents for panic disorder and social phobia. They are particularly effective in treatment-resistant depression and atypical depression. They are also used in the treatment of Parkinson's disease and several other disorders.
α-Methyltryptamine is a psychedelic, stimulant, and entactogen drug of the tryptamine class. It was originally developed as an antidepressant by workers at Upjohn in the 1960s, and was used briefly as an antidepressant in Russia under the trade name Indopan before being discontinued.
Banisteriopsis caapi, also known as ayahuasca, caapi or yagé (yage), is a South American liana of the family Malpighiaceae. It is one half of ayahuasca, a decoction with a long history of its entheogenic use and its status as a "plant teacher" among the Indigenous peoples of the Amazon rainforest.
β-Carboline (9H-pyrido[3,4-b]indole) represents the basic chemical structure for more than one hundred alkaloids and synthetic compounds. The effects of these substances depend on their respective substituent. Natural β-carbolines primarily influence brain functions but can also exhibit antioxidant effects. Synthetically designed β-carboline derivatives have recently been shown to have neuroprotective, cognitive enhancing and anti-cancer properties.
Several alkaloids that function as monoamine oxidase inhibitors (MAOIs) are found in the seeds of Peganum harmala, as well as tobacco leaves including harmine, harmaline, and harmalol, which are members of a group of substances with a similar chemical structure collectively known as harmala alkaloids. These alkaloids are of interest for their use in Amazonian shamanism, where they are derived from other plants. The harmala alkaloid harmine, once known as telepathine and banisterine, is a naturally occurring beta-carboline alkaloid that is structurally related to harmaline, and also found in the vine Banisteriopsis caapi. Tetrahydroharmine is also found in B. caapi and P. harmala. Dr. Alexander Shulgin has suggested that harmine may be a breakdown product of harmaline. Harmine and harmaline are both a reversible inhibitor of monoamine oxidase A (RIMAs). They can stimulate the central nervous system by inhibiting the metabolism of monoamine compounds such as serotonin and norepinephrine.
DET, also known under its chemical name N,N-diethyltryptamine and as T-9, is a psychedelic drug closely related to DMT and 4-HO-DET. However, despite its structural similarity to DMT, its activity is induced by an oral dose of around 50–100 mg, without the aid of MAO inhibitors, and the effects last for about 2–4 hours.
Harmine is a beta-carboline and a harmala alkaloid. It occurs in a number of different plants, most notably the Syrian rue and Banisteriopsis caapi. Harmine reversibly inhibits monoamine oxidase A (MAO-A), an enzyme which breaks down monoamines, making it a Reversible inhibitor of monoamine oxidase A (RIMA). Harmine does not inhibit MAO-B. Harmine is also known as banisterin, banisterine, telopathin, telepathine, leucoharmine and yagin, yageine.
Harmaline is a fluorescent indole alkaloid from the group of harmala alkaloids and beta-carbolines. It is the partially hydrogenated form of harmine.
Pharmahuasca is a pharmaceutical version of the entheogenic brew ayahuasca. Traditional ayahuasca is made by brewing the MAOI-containing Banisteriopsis caapi vine with a DMT-containing plant, such as Psychotria viridis. Pharmahuasca refers to a similar combination that uses a pharmaceutical MAOI instead of a plant.
Dopaminergic means "related to dopamine" (literally, "working on dopamine"), dopamine being a common neurotransmitter. Dopaminergic substances or actions increase dopamine-related activity in the brain. Dopaminergic brain pathways facilitate dopamine-related activity. For example, certain proteins such as the dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2), and dopamine receptors can be classified as dopaminergic, and neurons that synthesize or contain dopamine and synapses with dopamine receptors in them may also be labeled as dopaminergic. Enzymes that regulate the biosynthesis or metabolism of dopamine such as aromatic L-amino acid decarboxylase or DOPA decarboxylase, monoamine oxidase (MAO), and catechol O-methyl transferase (COMT) may be referred to as dopaminergic as well. Also, any endogenous or exogenous chemical substance that acts to affect dopamine receptors or dopamine release through indirect actions (for example, on neurons that synapse onto neurons that release dopamine or express dopamine receptors) can also be said to have dopaminergic effects, two prominent examples being opioids, which enhance dopamine release indirectly in the reward pathways, and some substituted amphetamines, which enhance dopamine release directly by binding to and inhibiting VMAT2.
Sceletium tortuosum is a succulent plant commonly found in South Africa, which is also known as Kanna, Channa, Kougoed —which literally means, 'chew(able) things' or 'something to chew'.
Harmalol is a bioactive beta-carboline and a member of the harmala alkaloids.
Tetrahydroharmol is a bioactive beta-carboline harmala alkaloid. It acts as a reversible inhibitor of monoamine oxidase A.
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 different compounds, it is one of the largest classes of alkaloids. Many of them possess significant physiological activity and some of them are used in medicine. The amino acid tryptophan is the biochemical precursor of indole alkaloids.
Tryptoline, also known as tetrahydro-β-carboline and tetrahydronorharmane, is a natural organic derivative of beta-carboline. It is an alkaloid chemically related to tryptamines. Derivatives of tryptoline have a variety of pharmacological properties and are known collectively as tryptolines.
6-MeO-THH, or 6-methoxy-1,2,3,4-tetrahydroharman, is a β-carboline derivative and a structural isomer of tetrahydroharmine (7-MeO-THH). 6-MeO-THH is mentioned in Alexander Shulgin's book TiHKAL, stating that 6-MeO-THH is very similar to the other carbolines. Limited testing suggests that it possesses mild psychoactive effects at 1.5 mg/kg and is said to be about one-third as potent as 6-methoxyharmalan. It has been isolated from certain plants of the Virola family.
Substituted tryptamines, or serotonin analogues, are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all tryptamines contain an indole ring, joined to an amino (NH2) group via an ethyl (−CH2–CH2−) sidechain. In substituted tryptamines, the indole ring, sidechain, and/or amino group are modified by substituting another group for one of the hydrogen (H) atoms.
A monoamine reuptake inhibitor (MRI) is a drug that acts as a reuptake inhibitor of one or more of the three major monoamine neurotransmitters serotonin, norepinephrine, and dopamine by blocking the action of one or more of the respective monoamine transporters (MATs), which include the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT). This in turn results in an increase in the synaptic concentrations of one or more of these neurotransmitters and therefore an increase in monoaminergic neurotransmission.