Eucommia ulmoides Oliv.(EuO),also known as Duzhong,native to China,has been reported to have antioxidative function,but its cellular mechanism is not fully examined yet.We investigated inhibitory effects of EuO leaf ethanol extracts on H2O2-induced apoptosis in rat osteoblastic MC3T3-E1 cells and underlying mechanisms.Locally-grown Duzhong leaves were extracted with ethanol.MC3T3-E1 cells were treated with EuO (6.25,12.5,25,50,and 100 μg/ml) for 24 h,and then H2O2 (800 μmol/L) for an additional 24 h.Cell survival rate,percentage of apoptosis,and expressions of caspases 3,6,7,and 9 were examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay,microscopic analysis,Western blotting,and reverse transcription polymerase chain reaction (RT-PCR).The final EuO leaf ethanol extract powder was detected to contain caffeotannic acid at 58 mg/g and geniposide at 3.45 mg/g by high performance liquid chromatography (HPLC).EuO remarkably restrained cell oxidative damage and increased cell survival rate in a dose-dependent manner: 0 μg/ml,0.21;6.25 μg/ml,0.28;12.5 μg/ml,0.31;25 μg/ml,0.48;50 μg/ml,0.54;and 100 μg/ml,0.66 (P<0.05),with the half-effective concentration being around 25 μg/ml.MTT results were confirmed by microscopic analysis.Western blotting and RT-PCR analyses showed that the expressions of caspases 3,6,7,and 9 were significantly decreased in the EuO-treated cells compared with the control (EuOand H2O2-free) (P<0.05),with the half-effective concentration of EuO ranging from 12.5 to 25 μg/ml.We conclude that the ethanol-extracted EuO leaf extracts promoted the growth of MC3T3-E1 cells,and suppressed the H2O2-induced apoptosis in a rat MC3T3-E1 osteogenic cell model,likely due to the inhibition of caspases’ activities.The results indicate that EuO is a potent antioxidant,which may contribute to its many cellular protective functions,including the promotion of bone growth. Eucommia ulmoides Oliv. (EuO), also known as Duzhong, native to China, has been reported to have antioxidant function, but its cellular mechanism is not known yet. We demonstrated inhibitory effects of EuO leaf ethanol extracts on H2O2-induced apoptosis in Lactally-grown Duzhong leaves were extracted with ethanol. MC3T3-E1 cells were treated with EuO (6.25,12.5,25,50, and 100 μg / ml) for 24 h, and then H2O2 (800 μmol / L) for an additional 24 h. Cell survival rate, percentage of apoptosis, and expressions of caspases 3,6,7, and 9 were examined using 3- (4,5-dimethylthiazol- , 5-diphenyltetrazolium bromide (MTT) assay, microscopic analysis, Western blotting, and reverse transcription polymerase chain reaction (RT-PCR). The final EuO leaf ethanol extract powder was detected to contain caffeotannic acid at 58 mg / g and geniposide at 3.45 mg / g by high performance liquid chromatography (HPLC) .EuO remarkably restrained cell oxidative damag and increased cell survival rate in a dose-dependent manner: 0 μg / ml, 0.21; 6.25 μg / ml, 0.28; 12.5 μg / ml, 0.31; 25 μg / ml, 0.48; μg / ml, 0.66 (P <0.05) with the half-effective concentration being around 25 μg / ml. MTT results were confirmed by microscopic analysis. Western blotting and RT-PCR analyzes showed that the expressions of caspases 3,6,7 , and 9 were significantly decreased in the EuO-treated cells compared with the control (EuO and H2O2-free) (P <0.05) with the half-effective concentration of EuO ranging from 12.5 to 25 μg / ml. We conclude that the ethanol -extracted EuO leaf extracts promoted the growth of MC3T3-E1 cells, and suppressed the H2O2-induced apoptosis in a rat MC3T3-E1 osteogenic cell model, likely due to the inhibition of caspases’ activities. The results that results that EuO is a potent antioxidant , which may contribute to its many cellular protective functions, including the promotion of bone growth.