Valerian (Caprifoliaceae family) is a perennial flowering plant, with heads of sweetly scented pink or white flowers that bloom in the summer months. The Caprifoliaceae or honeysuckle family are a clade of dicotyledonous flowering plants consisting of about 860 species in 42 genera, with a nearly cosmopolitan distribution.
Native to Europe and parts of Asia, valerian has been introduced into North America. It is consumed as food by the larvae of some Lepidoptera (butterfly and moth) species including Grey Pug.
Valerian, in pharmacology and herbal medicine, is the name of a herb or dietary supplement prepared from roots of the plant. Crude extract of the root is often sold in the form of capsules. Valerian root has sedative and anxiolytic effects. It can also be classified as a drug, since its consumption produces a sedative or medicinal effect, while it is not exclusively a type of food. These effects are suspected to be mediated through the GABA receptor. The amino acid valine is named after this plant.
Valerian has been used as a medicinal herb since at least the time of ancient Greece and Rome. Hippocrates described its properties, and Galen later prescribed it as a remedy for insomnia. In medieval Sweden, it was sometimes placed in the wedding clothes of the groom to ward off the "envy" of the elves. Valerian flower extracts were used as a perfume in the sixteenth century.
Valerian is most often used to treat insomnia. It can be considered an alternative treatment for hypnotic drugs. It is also sometimes used as an alternative for sedatives, such as benzodiazepines in the treatment of certain anxiety disorders. Whether or not valerian is an efficacious treatment for insomnia is still a very open question. Multiple recent systematic reviews of the medical research literature and meta-analyses have produced conflicting conclusions regarding the efficacy of the substance.
One systematic review and meta-analysis published in 2006 in the American Journal of Medicine concluded that "The available evidence suggests that valerian might improve sleep quality without producing side effects." An article in the Medical Science Monitor states that, "...based on cellular and animal studies as well as human clinical trials the literature supports a role for these preparations [including valerian root] as useful alternatives in the management of the stress and anxiety of everyday life." However, another systematic review, published in 2007 in the journal Sleep Medicine Reviews, concluded that valerian was safe but not clinically efficacious for insomnia.
Mechanism of Action
Because of valerian's historical use as a sedative, antiseptic, anticonvulsant, migraine treatment and pain reliever, most basic science research has been directed at the interaction of valerian constituents with the GABA neurotransmitter receptor system. Many studies remain inconclusive and all require clinical validation. The mechanism of action of valerian in general, and as a mild sedative in particular, has not been fully elucidated. However, it is generally believed that some of the GABA-analogs, particularly valerenic acids as components of the essential oil along with other semi-volatile sesquiterpenoids, appear to have some affinity for the GABAA receptor, a class of receptors on which benzodiazepines are known to act. Valeric acid, which is responsible for the typical odor of mostly older valerian roots, does not have any sedative properties.
Valerian also contains isovaltrate, which has been shown to be an inverse agonist for adenosine A1 receptor sites. This action likely does not contribute to the herb's sedative effects, which would be expected from an agonist, rather than an inverse agonist, at this particular binding site. Hydrophilic extractions of the herb commonly sold over-the-counter, however, probably do not contain significant amounts of isovaltrate. Valerenic acid in Valerian stimulates serotonin receptors as a partial agonist.