本研究利用兩種脂質過氧化作用之抑制作用模式系統，包括游離脂肪酸（亞麻油酸）系統與生理性脂質（血漿脂質）系統，來評估優格菌株胞內物的抗氧化能力。Streptococcus salivarius ssp. thermophilus ATCC 19258 和Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842 對亞麻油酸過氧化作用的抑制率分別為61%和57%，而S. salivarius ssp. thermophilus ATCC 19258 和L. delbrueckii ssp. bulgaricus ATCC 11842 對血漿脂質過氧化作用的抑制率分別為57%和41%，由這兩種脂質過氧化作用模式系統，證實這兩株優格菌株具有高度的抗氧化能力。本研究再進一步利用 Intestine 407 細胞株模式系統，來探討優格菌株的抗氧化能力對降低氧化劑過氧化氫所引起氧化傷害之效果，結果顯示優格菌株胞內物確實可以降低氧化劑過氧化氫的氧化性傷害，雖然 L. delbrueckii ssp. bulgaricus ATCC 11842 對降低 DNA 損傷的效果較弱，然而 S. salivarius ssp. thermophilus ATCC 19258 則表現對保護 Intestine407 對抗氧化劑過氧化氫所引起的基因毒性良好之能力。同時，這兩株優格菌株也發揮抑制過氧化氫細胞毒性的能力，S. salivarius ssp. thermophilusATCC 19258 和 L. delbrueckii ssp. bulgaricus ATCC 11842所表現的細胞毒性抑制率分別為71%和48%。

The antioxidative activity of intracellular extracts of yogurt bacteria was measured based on the inhibition of lipid peroxidation of two model systems, namely a free fatty acid (linoleic acid) system and a biological lipid (plasma lipid) system. The inhibitory rate on linoleic acid peroxidation was 61 and 57% for Streptococcus salivarius ssp. thermophilus ATCC 19258 and Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842, respectively. The inhibitory rate on plasma lipid peroxidation was 57 and 41% for S. salivarius ssp. thermophilus ATCC 19258 and L. delbrueckii ssp. bulgaricus ATCC 11842, respectively. Results from both systems demonstrated that these two yogurt strains were potentially highly antioxidative. Further experiments were done on Intestine 407 cells to determine the antioxidative effects of yogurt bacteria on reducing oxidative damage of oxidant H2O2. Intracellular extracts of yogurt bacteria reduced the genotoxicity of H2O2. Although L. delbrueckii ssp. bulgaricus ATCC 11842 had only minor effects on reducing DNA damage, S. salivarius ssp. thermophilus ATCC 19258 showed excellent potential for protecting the Intestine 407 cells from the genotoxicity of oxidant H2O2. Both yogurt bacteria demonstrated high cytotoxicity inhibitory ability for oxidant H2O2. The cytotoxicity inhibition rate was 71 and 48% for S. salivarius ssp. thermophilus ATCC 19258 and L. delbrueckii ssp. bulgaricus ATCC 11842, respectively.