Mechanistic insights into the bleaching of melanin by alkaline hydrogen peroxide

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JournalFree Radical Biology and Medicine
DateAccepted/In press - 14 Mar 2017
DateE-pub ahead of print - 18 Mar 2017
DatePublished (current) - 1 Jul 2017
Number of pages8
Pages (from-to)110-117
Early online date18/03/17
Original languageEnglish


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.

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    Research areas

  • Fenton chemistry, Hydrogen peroxide, Hydroxyl radical, Melanin bleaching, Reactive oxygen species, Superoxide


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