In recent years, interest in Hypericum perforatum has increased due to its antiviral, antidepressive and apoptosis-inducing properties. Plant material preparation after harvesting often includes dehydration or freezing and further storage, and these procedures can lead to variations in the secondary metabolite profile. In this study the effects of drying, freezing and storage at -20 ºC on flavonoid and hypericin content in H. perforatum were evaluated. Leaves and stems of H. perforatum were dried at 25, 30, 50 and 70 ºC, frozen in liquid nitrogen or frozen and then stored at -20 ºC for 10, 20 and 30 days. Flavonoid and hypericin quantification was performed by High Performance Liquid Chromatography (HPLC). Levels of both flavonoids and hypericin were affected by drying temperature. Drying at 25 ºC resulted in lower levels of most of the metabolites analyzed while at 50 ºC, levels of free and conjugated rutin, conjugated quercetin and quercitrin as well as hypericin content were maintained when compared to fresh samples. Free apigenin and kaempferol did not show any significant variation, regardless of drying temperature. Freezing did not affect the profile of flavonoids, but it led to significant reduction in hypericin content.
flavonoids; hypericin; secondary metabolism; medicinal plants; natural products
