Protective Effect of Sasa borealis Leaf Extract on AAPH-Induced Oxidative Stress in LLC-PK1 Cells

This study was designed to investigate the protective effect of Sasa borealis leaf extract on 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress in LLC-PK1 cells (porcine kidney epithelial cells). The butanol fraction from Sasa borealis leaf extract (SBBF) was used in this study because it possessed strong antioxidant activity and high yield among fractions. Exposure of LLC-PK1 cells to 1 mM AAPH for 24 hr resulted in a significant decrease in cell viability, but SBBF treatment protected LLC-PK1 cells from AAPH-induced cell damage in a dose dependant manner. To determine the protective action of SBBF against AAPH-induced damage of LLC-PK1 cells, we measured the effects of SBBF on lipid peroxidation and antioxidant enzymes activities of AAPH treated cells as well as scavenging activities on superoxide anion radical and hydroxyl radical. SBBF had a protective effect against the AAPH-induced LLC-PK1 cellular damage and decreased lipid peroxidation and increased activities of antioxidant enzymes such as superoxide dismutase and glutathione peroxidase. Furthermore, SBBF showed strong scavenging activity against superoxide anion radical. The $IC_{50}$ value of SBBF was $28.45{\pm}1.28\;{\mu}g/mL$ for superoxide anion radical scavenging activity. The SBBF also had high hydroxyl radical scavenging activity ($IC_{50}=31.09{\pm}3.08\;{\mu}g/mL$). These results indicate that SBBF protects AAPH-induced LLC-PK1 cells damage by inhibiting lipid peroxidation, increasing antioxidant enzyme activities and scavenging free radicals.