Okada Youji, Tanaka Kaoru, Sato Eisuke, Okajima Haruo
Department of Analytical Chemistry, Faculty of Health Sciences, Kyorin University, 476 Miyasita-cho, Hachioji, Tokyo, 192-8508, Japan.
Org Biomol Chem. 2006 Nov 21;4(22):4113-7. doi: 10.1039/b611506c.
We have undertaken a detailed study of the antioxidant activity of allicin, one of the main thiosulfinates in garlic, in order to obtain quantitative information on it as a chain-breaking antioxidant. The antioxidant actions of allicin against the oxidation of cumene and methyl linoleate (ML) in chlorobenzene were studied in detail using HPLC. The hydroperoxides formed during the course of the inhibited oxidation of ML were analyzed as their corresponding alcohols by HPLC, and it is apparent that an allylic hydrogen atom of the allicin is responsible for the antioxidant activity. Furthermore, it is clear that the radical-scavenging reactions of allicin proceed via a one-step hydrogen atom transfer based on the results of the reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) in the presence of Mg2+ and calculation of the ionization potential value. In addition, we determined the stoichiometric factor (n), the number of peroxyl radicals trapped by one antioxidant molecule, of allicin by measuring the reactivity toward DPPH in chlorobenzene, and the value of n for allicin was about 1.0. Therefore, we measured the rate constants, k(inh), for the reaction of allicin with peroxyl radicals during the induction period of the cumene and the ML oxidation. As a result, we found that allicin reacts with peroxyl radicals derived from cumene and ML with the rate constants k(inh) = 2.6 x 10(3) M(-1)s(-1) and 1.6 x 10(5) M(-1)s(-1) in chlorobenzene, respectively. Our results demonstrate for the first time reliable quantitative kinetic data and the antioxidative mechanism of allicin as an antioxidant.
我们对大蒜中的主要硫代亚磺酸酯之一大蒜素的抗氧化活性进行了详细研究，以便获取其作为链断裂抗氧化剂的定量信息。使用高效液相色谱法（HPLC）详细研究了大蒜素对氯苯中异丙苯和亚油酸甲酯（ML）氧化的抗氧化作用。通过HPLC将ML抑制氧化过程中形成的氢过氧化物分析为其相应的醇，很明显大蒜素的烯丙基氢原子负责抗氧化活性。此外，根据在Mg2+存在下与2,2-二苯基-1-苦基肼（DPPH）反应的结果以及电离势值的计算，很明显大蒜素的自由基清除反应通过一步氢原子转移进行。此外，我们通过测量在氯苯中对DPPH的反应性来确定大蒜素的化学计量因子（n），即一个抗氧化剂分子捕获的过氧自由基的数量，大蒜素的n值约为1.0。因此，我们测量了大蒜素在异丙苯和ML氧化诱导期与过氧自由基反应的速率常数k(inh)。结果，我们发现大蒜素在氯苯中分别以速率常数k(inh) = 2.6 x 10(3) M(-1)s(-1)和1.6 x 10(5) M(-1)s(-1)与源自异丙苯和ML的过氧自由基反应。我们的结果首次证明了大蒜素作为抗氧化剂的可靠定量动力学数据和抗氧化机制。
