In this study, the antioxidant potentials of crude extracts and solvent-partitioned fractions of Limonium tetragonum were assessed by measuring their ability to scavenge intracellular reactive oxygen species (ROS) generated in HT-1080 cells. Following activity-oriented separation, four flavonol glycosides were isolated as active principles and their chemical structures were determined by 2 D NMR and by comparison with reported spectral data. The isolated compounds (1-4) were evaluated for their antioxidant capacity using three different activity tests; degree of occurrence of intracellular ROS, lipid peroxidation in HT-1080 cells and the extent of oxidative damage of genomic DNA purified from HT-1080 cells. All compounds exhibited significantly inhibited the generation of intracellular ROS and lipid peroxidation in HT-1080 cells, and significantly inhibited DNA oxidation. In addition, direct free radical scavenging effects of these compounds were investigated using the electron spin resonance (ESR) spin-trap technique.