In our previous study, we have elucidated the chemical profile of YGS40, a fraction of Yi-Gan San (YGS), used for the treatment of Alzheimer's disease (AD). Oxidative stress-induced apoptosis is implicated in neurodegenerative disorders such as AD. The aim of the present study was to explore the protective effects of YGS40 against hydrogen peroxide (H2O2)-induced apoptosis in PC12 cells and the underlying mechanisms. PC12 cells were exposed to 100 μmol·L(-1) of H2O2 for 12 h with or without YGS40 pretreatment. Cytotoxicity was determined by MTT (3, (4, 5-dimethylthiazole-2-yl) 2, 5-diphenyl-tetrazolium bromide) and lactate dehydrogenase (LDH) release assays; apoptosis was detected by Annexin V/propidium iodide coupled staining and by determining caspase-3 activity and Bax and Bcl-2 protein levels. Mitochondrial membrane potential (MMP) was assessed by the retention of rhodamine123; and the activities of superoxide dismutase (SOD) and malondialdehyde (MDA) were measured using commercially available enzymatic kits. Pretreatment with YGS40 significantly prevented H2O2-induced cytotoxicity and protected the cells against H2O2-triggered apoptosis characterized by externalization of membrane phosphatidylserine and caspase-3 activation and the increased ratio of Bax/Bcl-2 in PC12 cells. Further studies showed that YGS40 suppressed H2O2-induced MMP loss, increased SOD activity, and decreased MDA level. These findings suggest that YGS40 may be beneficial for the prevention and treatment of oxidative stress-mediated disorders.