Effects of UV-B radiation on total phenolic, flavonoid and hypericin contents in Hypericum retusum Aucher grown under in vitro conditions

This study was conducted to increase total phenolics, flavonoids and hypericin accumulation in in vitro cultures of Hypericum retusum Aucher to determine the appropriate time of UV radiations. Proliferation of plantlets on Murashige-Skoog medium containing 0.5 mg L-1 N-6-benzylaminopurine was achieved under in vitro conditions. Then, the plantlets were exposed to UV-B radiation for different periods (15, 30, 45 and 60 min). The highest total phenolics, flavonoids and hypericin accumulation (43.17 +/- 0.8; 35.09 +/- 0.8; 2.7 +/- 0.05 mg g(-1), respectively) was achieved at 45 minutes of exposure to UV-B radiation when compared with the contents of naturally growing plants (23.33 +/- 0.9, 18.62 +/- 0.3 and 1.6 +/- 0.01 mg g(-1), respectively) and control groups (control group was not subjected to UV-B radiation).