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Tryptoline structure.png
IUPAC name
Other names
3D model (JSmol)
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PubChem CID
  • InChI=1S/C11H12N2/c1-2-4-10-8(3-1)9-5-6-12-7-11(9)13-10/h1-4,12-13H,5-7H2 Yes check.svgY
  • InChI=1/C11H12N2/c1-2-4-10-8(3-1)9-5-6-12-7-11(9)13-10/h1-4,12-13H,5-7H2
  • c1ccc2c(c1)c3c([nH]2)CNCC3
Molar mass 172.226 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.



Many tryptolines are competitive selective inhibitors of the enzyme monoamine oxidase type A (MAO-A). 5-Hydroxytryptoline and 5-methoxytryptoline (pinoline) are the most active monoamine oxidase inhibitors (MAOIs) with IC50s of 0.5 μM and 1.5 μM respectively, using 5-hydroxytryptamine (serotonin) as substrate.

Tryptolines are also potent reuptake inhibitors of serotonin and epinephrine, with a significantly greater selectivity for serotonin. Comparison of the inhibition kinetics of tetrahydro-β-carbolines for serotonin and epinephrine reuptake to that of the platelet aggregation response to these amines has shown that 5-hydroxymethtryptoline, methtryptoline, and tryptoline are poor inhibitors of reuptake. In all respects 5-hydroxytryptoline and 5-methoxytryptoline showed greater pharmacological activity than the tryptoline and methtryptoline.

Although the in vivo formation of tryptolines has been a matter of controversy, they have profound pharmacological activity.

See also

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<i>beta</i>-Carboline Chemical compound also known as norharmane

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Pinoline is a methoxylated tryptoline (5-methoxytryptoline) long claimed to be produced in the pineal gland during the metabolism of melatonin, however its pineal occurrence remains controversial. Its IUPAC name is 6-methoxy-1,2,3,4-tetrahydro-β-carboline, usually abbreviated as 6-MeO-THBC, and its more common name is a combination of "pineal beta-carboline". The biological activity of this molecule is of interest as a potential free radical scavenger, also known as an antioxidant, and as a monoamine oxidase A inhibitor.


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Serotonin–dopamine reuptake inhibitor

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