Abstract:To determine the optimal strontium （Sr） application level for tea plants and to investigate the antioxidant activity of strontium-enriched tea polyphenols （SETPs） as well as their protective effects against H2O2-induced oxidative damage in human LO2 hepatocytes， tea plants were subjected to Sr treatment using soil cultivation. SETPs were extracted by ultrasound-assisted ethanol extraction， and extraction parameters were optimized using the Box-Behnken response surface methodology. The in vitro antioxidant activity of SETPs was evaluated based on their scavenging capacities against DPPH， ABTS+， and hydroxyl radicals scavenging rates， and their Fe3+-reducing power. Furthermore， an H2O2-induced oxidative stress model in LO2 hepatocytes was established to assess the cytoprotective effects of SETPs. The results showed that the optimal Sr application level for tea plants was 50 mg/kg. The optimal extraction conditions for SETPs were determined as follows： ethanol volume fraction of 58%， solid-liquid ratio of 1∶46 （g/mL）， and extraction time of 35 min. Under these conditions， the extraction yield of polyphenols was （38.30±1.20）%. The scavenging rates of SETPs on DPPH radicals， ABTS+ radicals， hydroxyl radicals， and Fe3+ reducing power all increased with the elevation of mass concentration. SETPs significantly enhanced the viability of H2O2-treated LO2 hepatocytes， reaching 110.9% at 2 mg/mL， and markedly increased the activities of superoxide dismutase （SOD）， catalase （CAT），and glutathione peroxidase （GSH-Px） while reducing malondialdehyde （MDA） contents， thereby alleviating oxidative injury. In conclusion， SETPs exhibit strong antioxidant activity and confer protection against H2O2-induced oxidative damage in LO2 hepatocytes， providing a theoretical basis for their potential application in the development of functional foods.