Variation in concentrations of major bioactive compounds of St. John's wort: Effects of harvesting time, temperature and germplasm

St. John's wort (Hypericum perforatum L.) plants grown in a field or a greenhouse have been used for the preparation of phytopharmaceutical products. However, fields and greenhouse have such changeable environments, which can lead to high variations in the concentrations of bioactive compounds. In addition, due to the changeable environment, studies aiming to determine the effect of a unique environmental factor, the harvesting time or the germplasm on concentrations of bioactive compounds cannot be conclusive. In the current study, plants were grown in a growth chamber under controlled environments, and the effect of two different temperatures, 25 and 30°C, was determined on concentrations of the major bioactive compounds. Moreover, the variation in the concentrations of the major bioactive compounds with harvesting time, and germplasm lines were investigated. The concentrations of major bioactive compounds in the shoots reached a peak on day 52, regardless of the temperature. Throughout the experiment, pseudohypericin and hypericin concentrations were higher at 30°C than at 25°C, whereas hyperforin concentrations remained higher at 25°C than at 30°C. Moreover, high variations in the concentrations of the major bioactive compounds were found among the different germplasm lines.