Secondary metabolites in Hypericum perfoliatum: variation among plant parts and phenological stages
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The genus Hypericum is a source of biologically active compounds, notably hypericin and various phenolics. The concentrations of these compounds in plant tissues vary among plant parts and during the growing season. To determine this variation for Hypericum perfoliatum, a widespread species in Northern Turkey, wild-growing plants were harvested at five phenological stages: vegetative, floral budding, full flowering, fresh fruiting and mature fruiting. Whole shoots as well as individual parts (stems, leaves and reproductive tissues) were assayed for bioactive compounds by HPLC. In whole shoots, concentrations of secondary metabolites increased during shoot development. The highest concentrations of chlorogenic acid, hyperoside, quercitrin, quercetin and hypericin were reached when plants flowered, whereas rutin and apigenin-7-O-glucoside reached highest levels during fruit development. Of the individual plant parts, leaves did not contain any rutin, apigenin-7-O-glucoside and quercetin, and stems contained no hypericin. Reproductive parts had the highest levels of rutin, apigenin-7-O-glucoside, quercitrin, quercetin and hypericin, whereas leaves produced more chlorogenic acid and hyperoside. Compared to H. perforatum, a widely used medicinal plant, the tissues of H. perfoliatum contained similar concentrations of hypericin, less rutin, quercitrin and quercetin, and more chlorogenic acid and hyperoside. The presence of apigenin-7-O-glucoside had not been reported previously in the genus Hypericum.