| It is necessary for many living organisms to carry out the oxidation in vivo, although oxidative stress can damage biological molecules. The oxidative stress occurs when abnormally high levels of reactive oxygen species (ROS), such as superoxide radical anion (O2.-), hydrogen peroxide (H2O2), and hydroxyl radical (HO) were generated, which can result in the damages of DNA, protein and lipid. Oxidative damage plays a significant pathological role in human disease, such as emphysema, arthritis, atherosclerosis, cardiovascular diseases and cancer. The native antioxiddtive systems in organisms are not enough to prevent them from the oxidative damage. The addition of antioxidant may be a suitable choice to help reduction of oxidative damage. Among many kinds of antioxidants, natural antioxidants derived from microbes, plants, and anmals are more desirable, since there are doubts about the safety of synthetic chemical antioxidants.Lactic acid bacteria (LAB) are food grade bacteria with a GRAS (generally regarded as safe) status, which are widely used in food fermentation. The potential benefits of LAB for human health include stimulation of the immune, prevention of intestinal infection, reduction of serum cholesterol and antimutagenic effects. Resently, there are plenty of researches on the anticancer and antimutagenic activity of LAB. However, the researches on the antioxidative activity of LAB are reported only in recent years.In the present study, the LAB strain L3 and strain L4 were screened from 30 isolates of LAB according to the ability to inhabite linoleic acid peroxidation and scavenge 1,1-diphenyl-2-picrylhydrazl (DPPH) free radical. The cell-free extracts derived from the cultures of L3 and L4 showed strong antioxidative properties with chelate of Fe2+ by 54.3×10-6 and 41.3×10-6, scavenge of superoxide radical by 14.9% and 87.0%, scavenge of hydroxyl radical by 83.5% and 45.7%, and reducing activity was equivalent to 200 and 187μmol/L...
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