Hepatoprotective effect of Olea europaea L. leaf against oxidative stress in hepatocytes and zebrafish embryos.

Olea europaea L. leaf extract (OLE) exhibits hepatoprotective potential, yet its active components and the underlying mechanisms remain unclear. This study identifies the 60% ethanol-eluted OLE fraction as the most effective among the tested fractions on in vitro antioxidant activity and mitigation of H2O2-induced oxidative damage in L02 cells, and it was further validated in zebrafish embryos, significantly restoring viability and reducing ROS and lipid peroxidation. By integrating bioactivity data with HPLC fingerprinting, we established a spectrum-effect relationship, which pinpointed four active constituents: cynaroside, apigenin-7-O-glucoside, oleuroside, and ligustroside. These compounds were found to bind to the Keap1 protein, potentially activating the Nrf2 antioxidant pathway. These results clarify the active components and mechanism of action of OLE, supporting its development as a natural antioxidant for liver diseases.