title: Electrochemistry/mass spectrometry as a tool in the investigation of the potent skin sensitizer p-phenylenediamine and its reactivity toward nucleophiles.
abstract: BACKGROUND
  Although para-phenylenediamine (PPD) is known to cause severe allergic contact dermatitis in consequence of autoxidation and/or skin metabolism pathways, it is commonly utilized as an ingredient in permanent hair dyes. The aim of this work was to simultaneously accelerate the autoxidation process and to simulate the metabolic activation of PPD using a purely instrumental system.
  
  
  METHODS
  Electrochemistry (EC) in combination with electrospray ionization mass spectrometry (ESI-MS) was used in this study to assess the skin-sensitizing potential of PPD. Online and offline coupled EC/ESI-MS experiments were carried out and the emerging oxidation products were investigated. In a second approach, these primary species were allowed to react with the nucleophiles glutathione (GSH), cysteine (Cys), potassium cyanide (KCN) and lysine (Lys) in order to evaluate their reactivity.
  
  
  RESULTS
  The reactive p-phenylene quinone diimine (PPQD), which can form upon autoxidation and/or skin metabolism of PPD, was effectively generated in a simple EC cell next to further oxidation products, including the trimeric product Bandrowski's Base (BB). Conjugation with GSH and Cys was successfully proven, but no adducts with KCN or Lys were observed. Furthermore, the application of different concentration ratios between PPD and nucleophile was shown to play a crucial role concerning the type of oxidation products and adducts being formed.
  
  
  CONCLUSIONS
  It was found that EC/MS is a well-suited approach for the targeted generation of reactive haptens such as PPQD while avoiding detection problems due to the complexity of matrices encountered when conducting conventional in vitro or in vivo experiments.
authors.affiliation: University of Münster, Institute of Inorganic and Analytical Chemistry and NRW Graduate School of Chemistry, Corrensstr. 30, 48149 Münster, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Jahn
authors.forename: Helene
authors.initials: H
authors.lastname: Faber
authors.forename: Raniero
authors.initials: R
authors.lastname: Zazzeroni
authors.forename: Uwe
authors.initials: U
authors.lastname: Karst
mesh_terms: D000485:Allergens / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000379:methods*; D005978:Glutathione / Q000737:chemistry*; D008239:Lysine / Q000737:chemistry; D010084:Oxidation-Reduction; D010655:Phenylenediamines / Q000737:chemistry*; D011190:Potassium Cyanide / Q000737:chemistry; D023422:Skin Irritancy Tests / Q000379:methods; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000485:Allergens; D010655:Phenylenediamines; D005978:Glutathione; D008239:Lysine; D003545:Cysteine; D011190:Potassium Cyanide; C029728:4-phenylenediamine