This study was conducted to examine the neuroprotective effects of acetone extracts from Viola mandshurica (VME). The effect of VME on hydrogen peroxide (H(2)O(2))-induced DNA damage in PC12 cells was evaluated by the comet assay where VME (100 and 250 microg/mL) was a dose-dependent inhibitor of DNA damage induced by 500 micromol/L of H(2)O(2). The protective effect of VME against H(2)O(2)-induced oxidative damage on PC12 cells was investigated by an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] reduction assay and lactate dehydrogenase (LDH) release assays. After 3 h of cell exposure to 500 micromol/L of H(2)O(2), a marked reduction in cell survival was observed. However, the reduction was significantly prevented by 100 and 250 microg/mL of VME. H(2)O(2) also induced severe apoptosis of the PC12 cells, which was indicated by Hoechst 33342 staining. Interestingly, the H(2)O(2)-stressed PC12 cells that were incubated with 100 and 250 microg/mL of VME had greatly suppressed apoptosis. The results suggest that VME could be a new antioxidant candidate against neuronal diseases.