Valerian contains numerous active compounds which may be responsible for its properties. The essential oil of the root includes valerenic acid (valerian’s main bioactive component), monoterpenes (e.g., borneol, bornyl acetate), and other sesquiterpenes (e.g., valeric acid, isovaleric acid). The root also contains iridoid valepotriates (esters of short-chain fatty acids), lignans, volvalerenone A (a sesquiterpene),[1] and flavonoids.[2]
In vitro studies indicate that valerenic acid and valerenol may modulate gamma-aminobutyric acid (GABA) receptors by stimulating the GABA response in the nervous system.[2] This mechanism of action may underlie valerian’s sedative and anxiolytic effects.[3] However, significant GABAergic signaling after oral ingestion of valerian in humans has yet to be confirmed.
Additionally, in vitro research suggests that some components of valerian extract may also influence the serotonergic system due to their partial affinity for specific 5-HT (serotonin) receptors in the brain responsible for regulating the circadian rhythm.[2] Further research is required to substantiate these findings.
Finally, studies have observed an increase in the slow-wave sleep (SWS) phase (also known as the deep-sleep stage) following valerian supplementation.[4][5] This may explain why some studies reported an improvement in subjective sleep quality, while not demonstrating changes in other objective sleep measurements.[2]