In vitro studies have identified several flavonoids in chasteberry, especially casticin, which exerts opioidergic effects through activation of mu- and delta-opioid receptor subtypes ⁽²⁾. Casticin reduced lung inflammation in a murine model by inhibiting numbers of neutrophils, macrophages, and lymphocytes, and by reducing levels of proinflammatory cytokines and chemokines ⁽²⁵⁾.

Dopaminergic compounds, particularly clerodadienols, dose-dependently inhibited pituitary prolactin release, which could explain its effect during the premenstrual cycle when serum prolactin levels can be chronically elevated ⁽³⁾. Other diterpenes including rotundifuran also modulate dopamine receptors ⁽¹⁴⁾. Linoleic acid from chasteberry binds to estrogen receptors (ER) and can induce certain estrogen genes ⁽¹²⁾. The flavonoid apigenin was identified as the most active ER isoform-selective phytoestrogen ⁽¹¹⁾, and can also induce progestogenic activity ⁽¹³⁾.

In human studies, chasteberry restores progesterone concentrations, prolongs the hyperthermic phase in the basal temperature curve, and restores the luteinizing hormone-releasing hormone test to normal. It is thought to act on the pituitary-hypothalamic axis rather than directly on ovaries ⁽¹¹⁾.