Antioxidants in aerial parts ofHypericum sampsonii, Hypericum japonicumandHypericum perforatum

Antioxidants contents and antioxidative enzymes and their activities in fresh aerial tissues of Hypericum sampsonii (Sampson's St John's Wort), Hypericum japonicum (Japanese St John's Wort) and Hypericum perforatum were investigated. Hypericum sampsonii contained more total ascorbate [34.33 μmol g -1 fresh weight (FW)] than H. perforatum (57% less) and H. japonicum (82% less). It also contained more thiol and phenolics than two other species. Hypericum japonicum had highest superoxide dismutase (SOD) activity (8.74 mmol min -1 g -1 FW), followed by H. sampsonii (2% less) and H. perforatum (37% less). Hot-air dried H. perforatum materials contained more thiol [208.7 μmol g -1 dry weight (DW)] and phenolics (352.82 mg g -1 DW) than freeze-dried and fresh materials. Both drying treatments decreased the activities of antioxidative enzymes in aerial tissues of H. perforatum. However, freeze-dried H. perforatum contained the highest SOD activity (5.42 mmol min -1 g -1 DW) among the antioxidative enzymes measured from both freeze-dried and hot-air dried tissues (ranged from 0.02 to 2.65 μmol min -1 g -1 DW).