許多研究顯示乳酸菌具有抗氧化活性，避免自由基引起之DNA傷害。本研究探討10株分離自植物發酵液的乳酸菌之抗氧化活性，結果顯示10株乳酸菌的總抗氧化活性(TEAC) 為497.86-637.14 ppm ；DPPH去除率為13.02-42.72 ％。在乳酸菌避免自由基傷害DNA試驗中，使用250 mM H2O2傷害pUC19 DNA，結果顯示，10株乳酸菌均具有減少H2O2傷害DNA的功效。另使用MTT測試乳酸菌對於膀胱癌細胞 T-24 及小鼠肝臟細胞Clone 9之細胞毒性及保護效果，結果發現含4.0×107 CFU/mL至2.0×108 CFU/mL乳酸菌數之發酵液添加於T-24 及Clone 9之細胞，液T-24細胞存活率差異最為顯著者為乳酸菌B0008其存活率為93.44-8.61 ％，Clone 9細胞存活率差異最顯著為乳酸菌B0008其存活率為63.52-5.58 ％；但若將發酵液之 pH 調整為7.4後，乳酸菌發酵液對細胞之毒性降低，T24細胞存活率提升至90 ％以上而Clone 9細胞則於1.6×108 後才降至50 ％以下。利用過氧化物 (H2O2, 50mM) 傷害細胞，結果發現相當於乳酸菌菌數4.0×107 CFU/mL至2.0×10 8 CFU/mL之發酵液，T-24細胞的存活率由20.59 ％提升為48.38 ％而Clone 9細胞存活率則由15.72 ％提升至20.14 ％，顯示乳酸菌發酵液對H2O2傷害之細胞具有保護作用。
綜合上述之結果顯示本實驗所使用之10株乳酸菌發酵液均具有高度抗氧化能力，且對H2O2 傷害pUC 19 DNA及T-24或Clone 9細胞具有保護能力；乳酸菌發酵液經調整pH至7.4，並不會導致T-24及Clone 9細胞存活率下降，顯示乳酸菌發酵液對T-24及Clone 9細胞所產生之傷害，可能來自於乳酸菌產生之有機酸。 將細胞保護效果較佳之5株乳酸菌分離株進行16S rDNA 序列分析。結果顯示乳酸菌B0002、B0007 – B0010為Lactobacillus plantarum，乳酸菌B0006為Pediococcus acidilactici。 A number of studies indicated that lactic acid bacteria (LAB) posses antioxidant properties and may prevent DNA damage induced by reactive oxygen species (ROS). In this study, the antioxidant activities of LAB were monitored in total antioxidant activity and scavenging of DPPH. The results showed that the. The anti-oxidative 10 LAB isolates had Trolox equivalent antioxidant capacity (TEAC) from 497.86-637.14 ppm. Scavenging ability of DPPH radical was about 13.02-42.72％. Furthermore, we investigated the prevention of oxidative DNA damage by LAB cells, such as LAB in pUC DNA treated with hydrogen peroxide. Data showed that LAB reduced the DNA damage induced by H2O2 (250 mM). Additional experiments indicated that the reduction of oxidative damage was seen in fermented liquid than in cell-free extracts. When chemopreventive activity of LAB was evaluated, our data showed that LAB was able to reduce the DNA damage induced by H2O2 at pre and simultaneous protocols (0-60 min). Protection of T-24 and Clone 9 cell injury caused by hydrogen peroxide after incubation of LAB fermented culture was detected with MTT method. The results indicate that LAB fermented liquid were required for the prevention of cell damage. When cell numbers from 4.0×107 CFU/mL to 2.0×108 CFU/mL , the fermented liquid inhibited the cell proliferation and it was cytotoxic to T-24 and Clone 9 cell by lowering the survival to 96.31-7.94％. Cytotoxic activity was not found in adjusted pH 7.4 of fermented liquid, which might result from the organic acid produced by lactic acid bacteria. MTT method’s results showed the LAB fermented culture had strong scavenging ability on H2O2 after treated T-24 and Clone 9 cell by increasing the cell survival rate from 20.59％ to 48.38％ and 11.05％ to 48.38％ . Overall, our study showed that the 10 strains of LAB were protective against oxidative damage of pUC19 DNA, T-24 and Clone 9 cells induced by H2O2.
