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Valerian (Valeriana officinalis, Caprifoliaceae) is a perennial flowering plant, with heads of sweetly scented pink or white flowers that bloom in the summer months. Valerian flower extracts were used as a perfume in the sixteenth century.
Other names used for this plant include garden valerian (to distinguish it from other Valeriana species), garden heliotrope (although not related to Heliotropium) and all-heal (which is also used for plants in the genus Stachys). Red valerian, often grown in gardens, is also sometimes referred to as "valerian", but is a different species (Centranthus ruber) from the same family and not very closely related.
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. In the sixteenth century the Anabaptist reformer Pilgram Marpeck prescribed valerian tea for a sick woman.
Known compounds detected in valerian that may contribute to its method of action are:
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, but 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.
The chief constituent of valerian is a yellowish-green to brownish-yellow oil which is present in the dried root, varying from 0.5 to 2.0 percent, though an average yield rarely exceeds 0.8 percent. This variation in quantity is partly explained by location; a dry, stony soil yields a root richer in oil than one that is moist and fertile. The volatile oils that form the active ingredient are extremely pungent, somewhat reminiscent of well-matured cheese. Though some people remain partial to the earthy scent, some may find it to be unpleasant, comparing the odor to that of unwashed feet. Valerian tea should not be prepared with boiling water, as this may drive off the lighter oils.
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." However, another systematic review, published in 2007 in the journal Sleep Medicine Review, concluded that valerian was safe but not clinically efficacious for insomnia.
In the United States, valerian is sold as a nutritional supplement. Therapeutic use has increased as dietary supplements have gained in popularity, especially after the Dietary Supplement Health and Education Act was passed in 1994. This law allowed the distribution of many agents as over-the-counter supplements and therefore allowed them to bypass the regulatory requirements of the Food and Drug Administration (FDA).
Oral forms are available in both standardized and unstandardized forms. Standardized products may be preferable considering the wide variation of the chemicals in the dried root, as noted above. When standardized, it is done so as a percentage of valerenic acid or valeric acid.
Dosage is difficult to determine, due to the lack of standardization and variability in available forms. The United States Government's National Institutes of Health report that doses of 400–900 mg taken from 30 minutes to two hours before bed, or a lesser dose when combined with certain other supplements, have been researched.
Few adverse events attributable to valerian have been reported. Large doses may result in stomach ache, apathy, and a feeling of mental dullness or mild depression. Because of the herb's tranquilizer properties, it may cause dizziness or drowsiness, effects that should be considered before driving or operating heavy or hazardous equipment.
Because the compounds in valerian produce central nervous system depression, they should not be used with other depressants, such as ethanol, benzodiazepines, barbiturates, opiates, kava, or antihistamine drugs. Moreover, non-pregnant adult human hepatotoxicity has been associated with short-term use (i.e., a few days to several months) of herbal preparations containing valerian and Scutellaria (commonly called skullcap). Withdrawal after long-term use in a male has also been associated with benzodiazepine-like withdrawal symptoms, resulting in cardiac complications and delirium.
The very limited animal and human data do not allow a conclusion as to the safety of valerian during pregnancy. Moreover, as a natural, unregulated product, the concentration, contents, and presence of contaminants in valerian preparations cannot be easily determined. Because of this uncertainty and the potential for cytotoxicity in the fetus and hepatotoxicity in the mother, the product should be avoided during pregnancy.
An unusual feature of valerian is that valerian root and leaves are a cat attractant similar to, and as safe as catnip. Valerian contains the cat attractant actinidine. Cat attractants might mimic the odor of cat urine, which is caused by 3-mercapto-3-methylbutan-1-ol (MMB). Anecdotal reports claim that valerian is also attractive to rats—so much so that it had been used to bait traps. Stories describe the Pied Piper of Hamelin using both his pipes and valerian to attract rats. Research also shows that valerian root is the strongest chemo-attractant of slime molds (Physarum polycephalum).