中文摘要：

比较了嗜酸乳杆菌NCFM、植物乳杆菌ATCC 14917和植物乳杆菌NDC 75017这三株乳酸菌的抗氧化能力,初步探究乳酸菌发挥抗氧化作用的机制。通过羟自由基、超氧阴离子自由基、DPPH自由基清除实验,比较了三株乳酸菌菌体及发酵液自由基清除能力;将三株乳酸菌菌体及灭活菌体与受到H2O2诱导的氧化损伤Caco-2细胞共培养后,比较Caco-2细胞胞内两种抗氧化酶——超氧化物歧化酶（SOD）和谷胱甘肽过氧化物酶（GPx）的变化情况。结果表明,三株乳酸菌均具有一定的自由基清除能力,其中植物乳杆菌NDC 75017菌体具有最强的羟自由基清除能力;植物乳杆菌NDC 75017的发酵液具有最强的DPPH自由基清除能力,植物乳杆菌ATCC 14917发酵液具有最强的超氧阴离子自由基清除能力。另一方面,与正常细胞相比,受到氧化损伤的Caco-2细胞胞内SOD活性显著降低（P〈0.05）、GPx活性显著升高（P〈0.05）,三株乳酸菌的活菌均能不同程度缓解胞内SOD活性降低和GPx活性升高的情况,但灭活菌体的效果并不明显。

英文摘要：

To investigate the antioxidant mechanism of lactic acid bacteria（LAB）, we compared the antioxidant activity of Lactobacillus acidophi- lus NCFM, Lactobacillus plantarum ATCC 14917 and Lactobacillus plantarum NDC 75017. We compared the radical scavenging ability of the three strains and their fermentation solution by measuring their hydroxyl radical ~superoxide anion radical and DPPH radical scavenging activi- ty. To investigate the protective effect of three strains of LAB against hydrogen peroxide （H2O2）-induced oxidative stress in Caco-2 cells： af- ter exposed to H2O2, Caco-2 cells were treated with the three strains of LAB and their inactivated bacteria respectively, the activity of intra- cellular antioxidant enzymes, including superoxide dismutase （SOD） and glutathione peroxidase （GPx）, was measured to explain the antioxi- dant mechanism of LAB. The results indicate that the three strains of LAB possess some radical scavenging activity, L. plantarum NDC 75017 pos- sess the strongest hydroxyl radical scavenging activity, the fermentation solution of L. plantarum NDC 75017 have the strongest DPPH radical scavenging activity, and the fermentation solution of L. plantarum ATCC 14917 possess the strongest superoxide anion radical scavenging activity. On the other hand, compared with the normal Caco-2 cells, the activity of SOD had a significant decrease in the oxidative stress cells, and the GPx activity obviously increase in oxidative stress Caco-2 cells, all the three strains of LAB provided protection against H2O2-induced SOD ac- tivity reduction and GPx activity increased in different degrees, but the effect of inactivated bacteria is not obvious.