Amanullinic acid is a cyclic nonribosomal peptide.

It is an amatoxin, all of which are found in several members of the mushroom genus Amanita.

Amanullinic acid is relatively non-toxic( oral LD50 >20 mg/kg in mice).

[1] Like other amatoxins, amanullinic acid is an inhibitor of RNA polymerase II.