Human tyrosinase is able to oxidize both enantiomers of rhododendrol

Pigment Cell Melanoma Res. 2014 Nov;27(6):1149-53. doi: 10.1111/pcmr.12300. Epub 2014 Sep 3.


Racemic RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol, RD) was used as a topical skin-whitening agent until it was recently reported to induce leukoderma. We then showed that oxidation of RD with mushroom tyrosinase rapidly produces RD-quinone, which is quickly converted to RD-cyclic quinone and RD-hydroxy-p-quinone. In this study, we examined whether either or both of the enantiomers of RD can be oxidized by human tyrosinase. Using a chiral HPLC column, racemic RD was resolved optically to R(-)-RD and S(+)-RD enantiomers. In the presence of a catalytic amount of l-dopa, human tyrosinase, which can oxidize l-tyrosine but not d-tyrosine, was found to oxidize both R(-)- and S(+)-RD to give RD-catechol and its oxidation products. S(+)-RD was more effectively oxidized than l-tyrosine, while R(-)-RD was less effective. These results support the notion that the melanocyte toxicity of RD depends on its tyrosinase-catalyzed conversion to toxic quinones and the concomitant production of reactive oxygen species.

Keywords: human tyrosinase; melanocyte toxicity; rhododendrol; whitening agent.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Butanols / chemistry*
  • Butanols / metabolism*
  • Chromatography, High Pressure Liquid
  • Humans
  • Monophenol Monooxygenase / metabolism*
  • Oxidation-Reduction
  • Stereoisomerism
  • Time Factors


  • Butanols
  • rhododendrol
  • Monophenol Monooxygenase