Harmine and harmaline are β-carboline alkaloids, also called harmala alkaloids. In ayahuasca they do one key job: they block the enzyme monoamine oxidase A (MAO-A), which would otherwise break DMT down before it could act. A placebo-controlled study describes DMT on its own as “an orally labile psychedelic agent”, and notes that the brew’s β-carbolines, harmine, harmaline and tetrahydroharmine, inhibit MAO (Riba et al., 2003).
Riba’s team found very little harmine in the blood. They suggest it acts mainly in the gut and liver, and that blocking MAO there is enough to let DMT reach the circulation and the brain (Riba et al., 2003). The inhibition is reversible, which separates these alkaloids from the older irreversible MAO-inhibitor antidepressants. Even so, MAO inhibition is why combining ayahuasca with SSRIs and other serotonin-raising drugs is considered dangerous: together they can push serotonin activity too high.
Canada treats the two differently. The Controlled Drugs and Substances Act lists harmaline as item 9 and the related harmalol as item 10 of Schedule III, while harmine is not named in the schedule text. This is general information, not legal advice. Animal studies at high amounts have linked harmaline to harm in pregnancy and fetal development, but human data are thin.
Sources
- Riba et al., 2003, Journal of Pharmacology and Experimental Therapeutics: human pharmacology of ayahuasca
- McKenna, Towers and Abbott, 1984, Journal of Ethnopharmacology: MAO inhibitors in ayahuasca plants
- Controlled Drugs and Substances Act, Schedule III (Justice Laws)
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