Tryptoline, also known as tetrahydro-ò-carboline and tetrahydronorharmane, is a natural organic derivative of ò-carboline. It is an alkaloid chemically related to tryptamines. Derivatives of tryptoline have a variety of pharmacological properties and are known collectively as tryptolines.
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 IC<sub>50</sub>s of 0.5 üM and 1.5 üM respectively.
Tryptolines are also potent reuptake inhibitors of serotonin and epinephrine, with a significantly greater selectivity for serotonin.
In-vivo formation of tryptolines has been a matter of controversy.