Dept. of Medical Radiological Technology, Faculty of Health Sciences, Kyorin Univ., 5-4-1 Shimorenjaku Mitaka-shi, Tokyo, 181-8612, Japan.
J Food Sci. 2018 May;83(5):1265-1270. doi: 10.1111/1750-3841.14145. Epub 2018 Apr 16.
We re-examined the antioxidative mechanism of allicin as a radical scavenger on the basis of the reactivity toward 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and peroxyl radicals. Initially, it was found that allicin decomposed more rapidly in n-hexane and chlorobenzene than in acetonitrile, ethanol, and ethanol/water solutions and decomposed into ajoene and vinyldithiins in these solvents. Furthermore, the decomposition of allicin and the following formations of ajoene and vinyldithiins from allicin were accelerated by the reaction of allicin with DPPH and peroxyl radicals. These results show that 2-propenesulfenic acid, which arises by Cope elimination from allicin, is proposed to contribute to scavenge these radicals because ajoene and vinyldithiins were produced from allicin through the use of 2-propenesulfenic acid. Next, allicin was more effective at inhibiting the linoleic acid oxidation at 50 °C than at 30 °C and in cyclohexane than in acetonitrile. These results indicate that allicin decomposed rapidly at high temperatures in a hydrogen-bond-acceptor solution to 2-propenesulfenic acid. In addition, 2-propene-1-sulfinothionic acid S-methyl ester, which does not produce sulfenic acid through Cope elimination, has no activity against the radicals. On the other hand, methanesulfinothionic acid S-2-propenyl ester, which produces methanesulfenic acid through Cope elimination, has the same or increased activity as its allicin against the radicals. Based on these results, the Cope elimination product, sulfenic acid, from thiosulfinates with an α-sulfenyl proton was found to make a larger contribution to the radical scavenger than that of allicin itself.
We examined the antioxidant activity of allicin on the oxidation of cumene and linoleic acid in homogeneous solutions. It is obvious from these results that 2-propenesulfenic acid was found to make a larger contribution to the radical scavenger than that of allicin itself.
我们重新研究了大蒜素作为自由基清除剂的抗氧化机制，基于其对 2,2-二苯基-1-苦基肼（DPPH）和过氧自由基的反应性。最初，我们发现大蒜素在正己烷和氯苯中的分解速度比在乙腈、乙醇和乙醇/水溶液中快，并在这些溶剂中分解为蒜烯和烯丙基二硫。此外，大蒜素与 DPPH 和过氧自由基的反应加速了大蒜素的分解以及随后从大蒜素生成的蒜烯和烯丙基二硫。这些结果表明，由大蒜素发生 Cope 消除生成的 2-丙烯亚磺酸被认为有助于清除这些自由基，因为蒜烯和烯丙基二硫是通过使用 2-丙烯亚磺酸从大蒜素生成的。接下来，大蒜素在 50°C 下抑制亚油酸氧化的效果比在 30°C 下和在环己烷中比在乙腈中更好。这些结果表明，大蒜素在高温下在氢键受体溶液中迅速分解为 2-丙烯亚磺酸。此外，2-丙烯-1-亚磺硫代磺酸 S-甲酯，由于 Cope 消除不会生成亚磺酸，对自由基没有活性。另一方面，通过 Cope 消除生成甲磺酸亚磺酸的 2-丙烯基亚磺酰基酯，对自由基的活性与大蒜素相同或更高。基于这些结果，我们发现具有α-亚磺酰基质子的亚砜类化合物的 Cope 消除产物亚磺酸对自由基清除剂的贡献大于大蒜素本身。
我们在均相溶液中研究了大蒜素对枯烯和亚油酸氧化的抗氧化活性。从这些结果中可以明显看出，2-丙烯亚磺酸对自由基清除剂的贡献大于大蒜素本身。
