A convenient screening method to differentiate phenolic skin whitening tyrosinase inhibitors from leukoderma-inducing phenols. Issue 1 (October 2015)

• Record Type: Journal Article
• Authors: Ito, Shosuke; Wakamatsu, Kazumasa
• Is Part Of: Journal of dermatological science. Volume 80:Issue 1(2015:Oct.)
• Page Start: 18
• Page End: 24
• Publication Date: 2015-10
• Subjects: ESI electrospray ionization -- HPLC high-performance liquid chromatography -- MS mass spectrometry -- NMR nuclear magnetic resonance -- UV ultraviolet; Melanocyte toxicity -- Rhododendrol -- Tyrosinase -- Tyrosinase inhibitor -- Whitening agent; Dermatology -- Periodicals; Skin Diseases -- Periodicals; Dermatologie -- Périodiques; 616.5005
• DOI: 10.1016/j.jdermsci.2015.07.007
• Languages: English
• ISSNs: 0923-1811

Abstract

Highlights: Oxidation of phenols to ortho -quinones is followed by spectrophotometry and HPLC. Leukoderma-inducing phenols are oxidized by mushroom tyrosinase to toxic ortho -quinones. Phenolic tyrosinase inhibitors are not (or only slowly) oxidized by tyrosinase. Tyrosinase inhibitors should be examined as substrates if they are phenolic compounds. Abstract: Background: Tyrosinase is able to oxidize a great number of phenols and catechols to form ortho -quinones. Ortho -quinones are highly reactive compounds that exert cytotoxicity through binding with thiol enzymes and the production of reactive oxygen species. Certain phenolic (and catecholic) compounds are known to induce contact/occupational leukoderma through activation to ortho -quinones. Objective: We report a convenient screening method to follow the oxidation of those leukoderma-inducing phenols by mushroom tyrosinase. Methods: Oxidation of phenolic compounds by mushroom tyrosinase was followed periodically by UV–vis spectrophotometry. The production of ortho -quinones were confirmed by their absorptions around 400–420 nm. HPLC analysis after reduction with NaBH4 detected the corresponding catechols. Results: Leukoderma-inducing phenols, rhododendrol, raspberry ketone, 4-methoxyphenol, 4-benzyloxyphenol, 4- tert -butylphenol, and 4- tert -butylcatechol, were readily oxidized by mushroom tyrosinase to form ortho -quinones. On the other hand, phenolic skin whitening tyrosinase inhibitors, ellagic acid, 4- n -butylresorcinol, potassium 4-methoxysalicylate, and 2, 2′-dihydroxy-5, 5′-di- n -propylbiphenyl, were not oxidized by mushroom tyrosinase, while arbutin was only slowly oxidized. Conclusion: This study has provided a convenient screening method to differentiate phenolic skin whitening tyrosinase inhibitors from leukoderma-inducing phenols. A common chemical feature of the latter group of compounds is that they are readily oxidized by tyrosinase to form reactive ortho -quinone species. The present results point out the necessity that tyrosinase inhibitors should also be examined as substrates if they are phenolic compounds.