Hypericum spp.: A Resource from Wild Mediterranean Flora for the Treatment of Mild Depression

The genus Hypericum holds about 480 species (Crockett and Robson, 2011), widely spread throughout the world. A large part of them grows wild in the Mediterranean areas: 30 Hypericum taxa (26 species and 4 sub-species) have been detected in Italy, and about one third of them (11 taxa) are native to Sicily (Castellano and Spadaro, 2010). Actually, traditional and folk medicines in many parts of the world use Hypericum species for a plenty of different purposes. The most important are certainly two: the treatment of wounds and burns (because of the strong effects stimulating the formation of new tissue and lenitive of pain), and the therapy of moderate to mild depression (due to its remarkable hypnotic and tranquilizer effect, with specific antidepressant and anxiolytic effects). Besides these well-known actions, other biological effects of Hypericum extracts have been recognized in time, including antimicrobial, antioxidant, antiproliferative activities. Although many compounds have been identified in Hypericum extracts, however, which compound, or mixture of compounds, is exactly responsible for every specific pharmacological action it is not perfectly clear as far. The available literature agrees in ascribing a great importance to three active compounds, namely hypericin and pseudohypericin (two naphthodianthrones), and hyperforin (a phloroglucinol derivative). The occurrence of these substances in Hypericum extracts is highly variable, as an effect of both genetic factors (species and/or subspecies) and environmental conditions (growing site or cropping techniques). This paper makes a review of the information available in the newest literature about botanical and agronomical concerns, chemical composition and biological activity of Hypericum species, with a special emphasis to the treatment of depressive states. Original data about the content of hypericin, pseudohypericin and hyperforin in several Hypericum species and populations coming from different Italian sites are also exposed and discussed.