Yoshioka H, Ohashi Y, Akaboshi M, Senba Y, Yoshioka H
Radiochemistry Research Laboratory, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka-shi 422-8529, Japan.
Free Radic Res. 2001 Sep;35(3):265-71. doi: 10.1080/10715760100300801.
A new method using ESR spin trapping was proposed for measuring the scavenging activity of antioxidants for the hydroxyl (OH) radical. (-)-Epigallocatechin gallate (EGCg) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) were used as the antioxidant and spin trapping agent, respectively. The conventional method using a Fenton reaction had problems associated with the estimation of activity, because the antioxidant disturbs the system for generating OH radical by coordinating on Fe2+ and by consuming H2O2, besides scavenging the spin adduct (DMPO-OH). Intense gamma-irradiation was therefore used to generate OH radicals, and the intensity decrease in DMPO-OH after irradiation was followed to obtain the rate constant for the scavenging of DMPO-OH by EGCg. The intensities were extrapolated to zero time to estimate the quantity of DMPO-OH formed during gamma-irradiation. By using these values, the reaction rate constant between OH radical and EGCg was calculated as a ratio to that of DMPO. It was shown that this method is useful for comparing the OH radical-scavenging activity of various antioxidants.
提出了一种使用电子自旋共振（ESR）自旋捕集法来测量抗氧化剂对羟基（OH）自由基的清除活性。（-）-表没食子儿茶素没食子酸酯（EGCg）和5,5-二甲基-1-吡咯啉N-氧化物（DMPO）分别用作抗氧化剂和自旋捕集剂。使用芬顿反应的传统方法在活性评估方面存在问题，因为抗氧化剂除了清除自旋加合物（DMPO-OH）外，还会通过与Fe2+配位以及消耗H2O2来干扰产生OH自由基的体系。因此，采用强γ射线辐照来产生OH自由基，并跟踪辐照后DMPO-OH的强度降低情况，以获得EGCg清除DMPO-OH的速率常数。将强度外推至零时间，以估计γ射线辐照期间形成的DMPO-OH的量。通过使用这些值，计算出OH自由基与EGCg之间的反应速率常数，并与DMPO的反应速率常数进行比较。结果表明，该方法可用于比较各种抗氧化剂对OH自由基的清除活性。
