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Hypericin and pseudohypericin content in stems, leaves, and flowers of some Hypericum species growing in Turkey,, and H. triquetrifolium Turra, was determined by HPLC. Hypericin and pseudohypericin were detected in all species tested except for H. heterophyllum, and the presence in H. orientale and H. scabrum was reported by us for the first time in the current study. Hypericin and pseudohypericin contents observed in the study varied greatly depending on species and plant tissues. The lowest levels of hypericin and pseudohypericin were detected in leaves of H. hyssopifolium [0.030 and 0.051 mg/g dry weight (DW), respectively] whereas flowers of H. montbretii produced the highest levels of both hypericin forms (2.52 mg/g DW hypericin and 3.58 mg/g DW pseudohypericin). H. montbretti and H. triquetrifolium were found to be superior over H. perforatum with regard to hypericin and pseudohypericin content, encouraging the cultivation and biological evaluation of these species in Turkey.

Recent years has seen increasing interest in the genus Hypericum because it is the source of a variety of compounds and the biological activities of the genus are mainly derived from its hypericin content. The present study was conducted to determine whether this compound may be implicated as part of an inducible plant defense response in H. perforatum and H. pruinatum. Greenhouse-grown plants were inoculated with the plant pathogens Phytophthora capsici and Diploceras hypericinum. Hypericin levels of the Hypericum species increased significantly in response to inoculation with both pathogens. While up to now little effort has been made to determine whether hypericin is inducible by pathogen/herbivore attack or if it could play a role in plant defense, the present study indicates that hypericin is a component in inducible plant defense response of H. perforatum and H. pruinatum.

The genus Hypericum (Guttiferae) is a source of biologically active secondary metabolites, notably hyperforin, hypericins and various phenolics. In the present study the presence of the phloroglucinol derivative hyperforin, the naphthodianthrones hypericin and pseudohypericin, the phenylpropane chlorogenic acid and the flavonoids such as rutin, hyperoside, apigenin-7-O-glucoside, kaempferol, quercitrin, quercetin and amentoflavone were investigated in two Turkish species of Hypericum, namely, Hypericum scabrum L. and Hypericum bupleuroides Gris. The aerial parts representing a total of 30 individuals were collected at full flowering and dissected into floral, leaf and stem tissues. After being dried at room temperature, the plant materials were assayed for secondary metabolite concentrations by HPLC. All of the secondary metabolites examined were detected in both species at various levels depending on plant tissue except for hyperforin which was not accumulated in Hypericum scabrum. The presence of hyperforin and the phenolic compounds examined in both species were reported by us for the first time.

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