beta-Carboline alkaloids in Peganum harmala and inhibition of human monoamine oxidase (MAO).
Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association March 1, 2010 T Herraiz, D González, C Ancín-Azpilicueta et al.
Peganum harmala (Syrian rue) seeds and roots contain high levels of beta-carboline alkaloids—harmine, harmaline, harmalol, harmol, and tetrahydroharmine—that strongly and selectively inhibit human monoamine oxidase A (MAO-A), with seed extracts having an IC50 of 27 µg/L and root extracts an IC50 of 159 µg/L. Stems, leaves, and flowers have little to no alkaloids and are poor MAO inhibitors. The potent MAO-A inhibition by seed and root extracts likely contributes to the plant's psychoactive and toxic effects and may underlie its traditional use as an antidepressant.