Although the many of the psychoactive properties of the passionflower are still awaiting more research, a great deal is already known.
One of the major active compounds contained within passionflower is the alkaloid harmine, - the same alkaloid group also occurs naturally in Banisteriopsis caapi and the Syrian rue. Harmine acts as a natural MAO-A inhibitor, preventing the breakdown of neurotransmitters such as serotonin and dopamine. Many pharmaceutical anti-depressant drugs are making use of this same MAOI mechanism, although synthetic MAOIs have been associated with more dangerous food and drug interactions.
In addition to harmala alkaloids, passionflower contains luteolin, chrysin and apigenin. How these substances work in synergy to create the relaxing and sedative effects is little understood.
Passionflower has also been found to contain large doses of GABA, which interact with GABA receptors in the body. GABA receptor activation reduces Central Nervous System activity, stopping it from becoming too “excitable” - this also explains some of the sedative effects Passionflower exhibits.