Apigenin might reduce levels of cortisol, the stress hormone. When human adrenal cells (in vitro) were exposed to flavonoid mixtures that included apigenin as a component in a range of concentrations of 12.5–100 micromolar, cortisol production decreased by up to 47.3% compared to control cells.[1][2]
In mice, apigenin extracted from the plant Cephalotaxus sinensis, a member of the plum yew family, increased the physiologic response to insulin.[3] These results have not yet been replicated in humans; in a study that gave participants a black pepper beverage that contained apigenin and a wheat bread challenge meal, blood glucose and insulin were no different from the control beverage group.[4]
Reproductive hormones such as testosterone and estrogen may also be affected by apigenin. In preclinical (animal) studies, apigenin modified enzyme receptors and activity in a way that suggests it could potentially affect testosterone activity, even at relatively low concentrations (5–10 micromolar).[5][6]
Breast cancer cells exposed to apigenin at a concentration of 20 micromolar for 72 hours showed inhibited proliferation through control of estrogen receptors.[7] Similarly, when ovarian cells were exposed to apigenin, aromatase activity was inhibited, and this is thought to be a possible mechanism in the prevention and treatment of breast cancer.[8] It is still unclear, however, how these effects would translate into an oral dose for human consumption.