Indole Alkaloids

The class is usually organized by how much extra carbon skeleton has been grafted onto the indole core:

Simple tryptamines

DMT, psilocybin, bufotenin, serotonin itself

Beta-carbolines

harmine, harmaline, the harmala alkaloids

Monoterpene indole alkaloids

the largest group: vincamine, mitragynine, reserpine, yohimbine, the Vinca and Rauwolfia alkaloids

Ergolines

the ergot and morning-glory lysergamides

Bisindoles

vinblastine and vincristine

Concentrated in a few large families, notably the dogbanes, coffees and nightshades:

No other plant compound class has contributed as much to medicine. Vinblastine and vincristine remain frontline chemotherapy agents; reserpine was the first effective antihypertensive and helped establish the monoamine theory of depression; the ergot alkaloids gave rise to the triptan migraine drugs and to bromocriptine.

On the herbal side, the beta-carbolines are reversible MAO-A inhibitors — the pharmacological basis of ayahuasca, where they render orally-inactive DMT active — and mitragynine is a partial opioid-receptor agonist with an atypical profile that has driven kratom's contested rise.