New Potential Pharmaceutical Applications of Hypericum Species

The genus Hypericum includes more than 450 species distributed in Europe, North America, North Africa and West Asia. These plants are widely used in folk medicine for the treatment of inflammation, bacterial and viral infections, burns and gastric disorders. The use for alleviating inflammation and promoting wound healing is well known for H. Perforatum L. (St. John's wort) and other species. Because of its pharmacological activity, H. perforatum L. is one of the most important species of this genus. This plant has been largely utilized for its efficacy in the treatment of mild to moderate depression. However, some other species have been utilized in traditional medicine and have been studied for their phytochemical composition and for their biological activities to date. Hypericum species contain biologically active secondary metabolites belonging to at least ten different classes, with prevalence of naphthodianthrones (hypericin and pseudohypericin), phloroglucinols (hyperforin), flavonoids (rutin, hyperoside, isoquercitrin, quercitrin, quercetin, amentoflavone) and phenylpropanoids (chlorogenic acid). However, great variations in contents have been reported for wild populations worldwide. The purpose of this review is to provide an overview of most recent studies about potential pharmaceutical applications of plants belonging to Hypericum genus. The most interesting isolated active principles and both in vitro and in vivo effects of Hypericum extracts are presented and discussed.