Abstract: Objective:To investigate the inhibitive effect of Cyanidin-3-O-glucoside (C3G) on oxidative stress in human embryonic kidney cells (HEK-293). Methods:Cell viability, MDA level and the level of intracellular reactive oxygen species (ROS) were investigated. Quantitative real-time PCR and Western blotting were used to detect the expression of Nrf2 and Kelch-like ECH associated protein 1 (Keap1). Results:After pretreatment with C3G, the cell viability was significantly higher than that of the injury group and increased in a concentration-dependent manner (p<0.05). The fluorescence intensity of oxidative DCF in injured group was increased compared with control group, and the ROS content of injured group was twice greater then control group. The fluorescence intensity of cells which pretreated with C3G was gradually weakened. The ROS content of C3G group decreased in a concentration-dependent manner. After pretreatment of C3G, the MDA levels decreased in a concentration-dependent manner. Furthermore, the protein and mRNA expressions of Nrf2 were significantly enhanced by 1.25, 5 and 20 μmol/L of C3G (p<0.05). The protein expression of Keap1 was significantly lower than that of injury group, and the mRNA expression of Keap1 was significantly down-regulated by 5 and 20 μmol/L of C3G. Conclusion:These results demonstrated that C3G protect HEK-293 cells against H₂O₂-induced oxidative stress through reducing intracellular ROS and MDA, as well as activating Nrf2/Keap1 signaling pathway.