Anti-oxidative effects by the extract of the biennial flower of Panax notoginseng against H
-induced cytotoxicity in PC12 cells. A: Various concentrations of H2O2 (0, 1.7, 3.4, 6.8 and 13.6 μg/ml) were added onto cultured PC12 cells, incubated for 24 hours and determined with cell viability assay. B: Extracts (1 mg/ml) from biennial flower, stem-leaf, rhizome and fiber root of Panax notoginseng were pre-treated with PC12 cells for 24 hours before the addition of H2O2 (13.6 μg/ml) for cytotoxicity test as in [A]. Vitamin C (35.2 μg/ml) served as a positive control. Data were expressed as% of control where the value of untreated culture was set as 100%, Mean ± SD, n = 4. Statistical significance is indicated as * P = 0.0412 for root-rhizome vs control); ** P = 0.00826 for biennial flower vs root-rhizome and *** P = 0.000215 for biennial flower vs control.