β-carbolines are alkaloids built on a three-ring system related to the indole. The ayahuasca vine, Banisteriopsis caapi, contains three main ones: harmine, harmaline and tetrahydroharmine. A 1984 analysis found that β-carbolines are highly active, reversible inhibitors of monoamine oxidase in a test-tube assay, and proposed that this protects DMT in the brew from breakdown (McKenna, Towers and Abbott, 198490003-5)).
The three do not act alike: a 1999 study describes harmine and harmaline as reversible MAO-A inhibitors, while tetrahydroharmine weakly blocks serotonin reuptake (Callaway et al., 199900168-8)). A 2022 review adds that β-carbolines also occur in many foods and in tobacco, and that reversible inhibitors almost never achieve complete MAO inhibition (Berlowitz, Egger and Cumming, 2022).
Blocking MAO-A, which also clears serotonin, is why researchers warn that combining these alkaloids with SSRI antidepressants may cause serotonin syndrome (Callaway and Grob, 1998). In Canada, harmaline and harmalol are listed in Schedule III of the Controlled Drugs and Substances Act, while harmine is not named (CDSA). This is not medical or legal advice.
Sources
- McKenna, Towers and Abbott, 1984, Journal of Ethnopharmacology
- Callaway et al., 1999, Journal of Ethnopharmacology: ayahuasca pharmacokinetics
- Berlowitz, Egger and Cumming, 2022, Frontiers in Pharmacology
- Controlled Drugs and Substances Act, Schedule III (Justice Laws)
Last checked .