Smith R A W, Garrett B, Naqvi K R, Fülöp A, Godfrey S P, Marsh J M, Chechik V
Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
Procter & Gamble Service GmbH, Sulzbacher Str. 40, 65824 Schwalbach am Taunus, Germany.
Free Radic Biol Med. 2017 Jul;108:110-117. doi: 10.1016/j.freeradbiomed.2017.03.014. Epub 2017 Mar 18.
This work aims to determine the roles of reactive oxygen species HO∙ and HO in the bleaching of melanins by alkaline hydrogen peroxide. Experiments using melanosomes isolated from human hair indicated that the HO∙ radical generated in the outside solution does not contribute significantly to bleaching. However, studies using soluble Sepia melanin demonstrated that both HO and HO∙ will individually bleach melanin. Additionally, when both oxidants are present, bleaching is increased dramatically in both rate and extent. Careful experimental design enabled the separation of the roles and effects of these key reactive species, HO∙ and HO. Rationalisation of the results presented, and review of previous literature, allowed the postulation of a simplified general scheme whereby the strong oxidant HO∙ is able to pre-oxidise melanin units to o-quinones enabling more facile ring opening by the more nucleophilic HO. In this manner the efficiency of the roles of both species is maximised.
这项工作旨在确定活性氧HO∙和HO在碱性过氧化氢对黑色素的漂白过程中所起的作用。使用从人发中分离出的黑素小体进行的实验表明，外部溶液中产生的HO∙自由基对漂白作用贡献不大。然而，使用可溶性乌贼墨黑色素的研究表明，HO和HO∙均可单独使黑色素漂白。此外，当两种氧化剂同时存在时，漂白的速率和程度都会显著增加。精心设计的实验能够区分这些关键活性物质HO∙和HO的作用与影响。对所呈现结果的合理分析以及对先前文献的回顾，使得我们能够提出一个简化的通用方案，即强氧化剂HO∙能够将黑色素单元预氧化为邻醌，从而使亲核性更强的HO更易于实现开环。通过这种方式，两种物质的作用效率得以最大化。
