Nomenclature Historical literature provides many explanations as to how St. John's wort got its name, most of them stemming from the herb's association with St. John the Baptist. The flowers also exude a red pigment said to be associated with the blood of St. John, and there was an ancient English tradition of throwing the flowers into a bonfire on the eve of St. John's Day. The species name perforatum is associated with the translucent leaf glands that can be seen as apparent perforations when held up to light. The yellow flowers are often marked with black dots along each of the five linear-lanceolate petals. Native to all of Europe and Asia except for the Arctic regions, H. perforatum is naturalized in the United States.
Ranchers consider it to be a noxious weed in pastures.
The major medical herbalists of ancient times, including Hippocrates, Pliny, Dioscorides, Theophrastus and Galen, wrote about the medicinal properties of St. John's wort, noting its uses as a vulnerary, diuretic, and for neuralgic conditions such as sciatica and hip pain. Chemistry St. John's wort contains numerous compounds with documented biological activity. Most researchers consider its effects to be due to a variety of constituents rather than any single compound. Constituents that have stimulated the most interest are the napthodianthrones hypericin and pseudohypericin, a broad range of flavonoids including quercetin, quercetrin, amentoflavone, and hyperin, the phloroglucinols hyperforin and adhyperforin, the essential oil, and, in some species, xanthones. St. John's wort is the most widely used antidepressant in Germany, where it outsells conventional antidepressants.