beta-Carboline

β-Carboline (9H-pyridoindole), also known as norharmane, is a nitrogen containing heterocycle. It is also the prototype of a class of compounds known as β-carbolines. β-Carboline (9H-pyridoindole), also known as norharmane, is a nitrogen containing heterocycle. It is also the prototype of a class of compounds known as β-carbolines. β-Carboline alkaloids are widespread in plants and animals, and frequently act as GABAA inverse agonists. As components of the liana Banisteriopsis caapi, the β-carbolines harmine, harmaline, and tetrahydroharmine play a pivotal role in the pharmacology of the indigenous psychedelic drug ayahuasca by preventing the breakdown of dimethyltryptamine in the gut by reversibly inhibiting monoamine oxidase, thus making it psychoactive upon oral administration. Some β-carbolines, notably tryptoline and pinoline, may be formed naturally in the human body. The latter is possibly implicated along with melatonin in the role of the pineal gland in regulating the sleep-wake cycle. β-carboline is a GABAA benzodiazepine site inverse agonist and can therefore have convulsive, anxiogenic and memory enhancing effects. 9-Methyl-β-carbolines appear to induce DNA damage when exposed to ultra-violet light. β-Carboline belongs to the group of indole alkaloids and consist of pyridine ring that is fused to an indole skeleton. The structure of β-carboline is similar to that of tryptamine, with the ethylamine chain re-connected to the indole ring via an extra carbon atom, to produce a three-ringed structure. The biosynthesis of β-carbolines is believed to follow this route from analogous tryptamines. Different levels of saturation are possible in the third ring, which is indicated here in the structural formula by colouring the optionally double bonds red and blue: