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This work aims to determine the roles of reactive oxygen species HO∙ and HO2 − 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 HO2 − 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 HO2 −. 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 HO2 −. In this manner the efficiency of the roles of both species is maximised.
|Number of pages||8|
|Journal||Free Radical Biology and Medicine|
|Early online date||18 Mar 2017|
|Publication status||Published - 1 Jul 2017|
Bibliographical note© 2017, Elsevier Inc. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.
- Fenton chemistry
- Hydrogen peroxide
- Hydroxyl radical
- Melanin bleaching
- Reactive oxygen species