The alkaloid constituents harman and harmaline are thought to produce monoamine oxidase inhibition ⁽¹⁾, while maltol and gamma-pyrone derivatives cause activation of gamma amino butyric acid (GABA) receptors that may account for anxiolytic and sedative properties ⁽¹¹⁾. Chrysin has also been identified among the bioactive metabolites with central nervous system (CNS) suppression activity ⁽²¹⁾.

In vitro, modulation of the GABA system by passionflower includes affinity to GABA(A) and GABA(B) receptors, and effects on GABA uptake ⁽²⁴⁾. Antiradical activities observed are attributed to flavonoids such as isovitexin ⁽²⁵⁾. An isolated benzoflavone moiety is suspected as being the strongest aromatase inhibitor in passionflower, although the flavone chrysin also has these properties ⁽²⁶⁾.

In an animal reproductive and developmental study, passionflower produced sexual behavioral disruption in male adult rats that was not accompanied by alterations in plasma testosterone levels, reproductive-related organs, and glands weights or sperm count, and was potentially attributed to aromatase inhibition ⁽²⁷⁾. In seizure models, protection against post-ictal depression not seen with diazepam controls point to activity from metabolites in passionflower rather than as a result of its seizure suppression effects ⁽²¹⁾.

Passionflower also exhibits mild anti-inflammatory activity. An ethanolic extract of passionflower reduced carrageenan-induced edema, leukocyte migration, and granuloma formation in mice, although the effect was less than that seen with aspirin ⁽¹³⁾.