Beta-carboline reversible MAO-A inhibitor

Plain-language summaryIntrigue 60 / 100

Harmaline is one of the three main beta-carboline alkaloids in the ayahuasca vine (Banisteriopsis caapi) and Syrian rue (Peganum harmala). Its critical pharmacological role is reversible MAO-A inhibition, which is what allows oral DMT to reach the brain in ayahuasca brews (without an MAO-A inhibitor, gut MAO destroys oral DMT before it can act centrally). Harmaline by itself produces vivid closed-eye visual imagery at high doses but is not a classical psychedelic. The reversible MAO inhibition is safer than the irreversible MAO inhibitors used as antidepressants but still creates real food and drug interaction risks. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundNiche research probe

34/100

A reference MAO-A inhibitor and tremor-model tool with limited novelty and thin standalone clinical signal

Harmaline is one of those compounds that earns its place in a research library not because it’s novel or therapeutically exciting, but because it does a specific job that’s hard to replicate. The beta-carboline skeleton, shared with harmine and tetrahydroharmine, has been pulling double duty in ethnobotanical and neuropharmacology research for decades, and harmaline’s particular profile, reversible MAO-A inhibition with good selectivity over MAO-B (Ki around 5 µM at human MAO-A, over 100-fold selectivity), makes it a reference compound worth having around.

The MAO-A story is the center of gravity here. As one of the primary harmala alkaloids in ayahuasca preparations, harmaline’s pharmacological role is well understood: it inhibits intestinal and hepatic MAO-A, which would otherwise degrade DMT before systemic absorption. That’s genuinely important for understanding the brew’s oral bioavailability, but it also means harmaline’s most studied context is inseparable from a multi-compound mixture. Isolating its specific contributions to human pharmacology in that context is messy, and standalone human data on harmaline is thin.

What we find more interesting from a bench standpoint is the tremor model. Harmaline-induced tremor in rodents is one of the few pharmacologically validated animal models of essential tremor, and it’s been used across dozens of labs to probe the cerebello-olivary system, test tremor-suppressing drug candidates, and understand the oscillatory physiology underlying the condition. For labs working on motor control or essential tremor biology, harmaline isnt a curiosity, it’s infrastructure.

Outside the tremor work, the compound has some utility as a broader beta-carboline pharmacology probe. The class hits multiple targets at varying concentrations, including sigma receptors and some NMDA interactions at higher doses, and harmaline lets you explore that pharmacology with a reversible agent that clears reasonably fast (plasma half-life roughly 2 to 3 hours). That’s useful for experimental designs where you need to avoid prolonged MAO-A suppression and want a cleaner washout window than irreversible inhibitors allow.

What limits the score is that the mechanism landscape is mature. Reversible MAO-A inhibition as a pharmacological concept is not new ground; moclobemide covers the clinical story more cleanly, harmine covers much of the same structural territory with arguably more CNS penetration literature, and the therapeutic promise of harmaline specifically is low. The translational signal outside of ayahuasca context is weak. We think this one belongs in the library as a reference and model compound, not as a frontier research target. The score reflects that honestly.

Novelty: 20
Mechanism promise: 35
In-category differentiation: 32
Evidence quality: 45
Translational signal: 25
Research bench value: 62

Rationale Harmaline’s score is driven by its genuine but narrow bench utility: the harmaline-induced tremor model is a pharmacologically validated rodent model of essential tremor used across many labs, and its rMAO-A selectivity profile (Ki ~5 µM, >100-fold over MAO-B) makes it a useful reference compound. Novelty, mechanism, differentiation, and translational scores are low because the pharmacology is mature, the clinical picture outside the ayahuasca context is thin, and better alternatives exist for most of what it does.

Beta-carboline reversible MAO-A inhibitor

A beta-carboline alkaloid from Peganum harmala and Banisteriopsis caapi; a reversible MAO-A inhibitor and component of ayahuasca.

Abstract

Harmaline (4,9-dihydro-7-methoxy-1-methyl-3H-pyrido[3,4-b]indole; CAS 304-21-2; molecular formula C13H14N2O; molecular weight 214.27) is a beta-carboline alkaloid isolated from Peganum harmala (Syrian rue) and Banisteriopsis caapi (ayahuasca vine). The compound is a reversible MAO-A inhibitor (Ki approximately 5 microM at human MAO-A) with greater than 100-fold selectivity over MAO-B; this reversible MAO-A inhibition is central to the pharmacology of ayahuasca, where harmaline (and harmine) prevent intestinal breakdown of the DMT in the brew, allowing oral activity. Harmaline itself has serotonergic and tremorgenic effects in animals and mild psychoactive effects in humans. Plasma half-life is approximately 2 to 3 hours. Used as a reference reversible MAO-A inhibitor and as a research probe for beta-carboline pharmacology.

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Tag: Beta-carboline reversible MAO-A inhibitor

Harmaline

Abstract

Read the full monograph