Apigenin is a naturally occurring flavonoid found in many plants, including parsley, chamomile, and celery. It has been investigated for its effects on the nervous system and, specifically, its potential to support the parasympathetic nervous system (PNS), which is responsible for "rest and digest" activities in the body. Scientific studies suggest that apigenin exerts anxiolytic (anxiety-reducing) and sedative effects, primarily through modulation of the GABA_A receptors, which are inhibitory neurotransmitter receptors in the central nervous system. Activation of these receptors is closely linked to enhanced parasympathetic tone and reduced sympathetic ("fight or flight") activity.

Animal studies have shown that administration of apigenin can lead to reduced anxiety-like behaviors and improved sleep quality, both of which are associated with increased parasympathetic activity. In particular, a study in mice demonstrated that apigenin could bind to benzodiazepine sites on GABA_A receptors, suggesting a mechanism similar to that of some pharmaceutical anxiolytics and sedatives. Human clinical research is still emerging, but the available preclinical data provides a plausible scientific rationale for apigenin's use in supporting the PNS. However, more robust human trials are needed to firmly establish its efficacy and safety for this specific purpose.