Electrochemical oxidation and protein adduct formation of aniline: a liquid chromatography/mass spectrometry study |
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Authors: | Daniel?Melles Torsten?Vielhaber Anne?Baumann Raniero?Zazzeroni Email author" target="_blank">Uwe?KarstEmail author |
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Institution: | 1.Westf?lische Wilhelms-Universit?t Münster, Institut für Anorganische und Analytische Chemie,Münster,Germany;2.Unilever U.K., Safety & Environmental Assurance Centre,Beds,UK |
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Abstract: | Historically, skin sensitization tests are typically based on in vivo animal tests. However, for substances used in cosmetic
products, these tests have to be replaced according to the European Commission regulation no. 1223/2009. Modification of skin
proteins by electrophilic chemicals is a key process associated with the induction of skin sensitization. The present study
investigates the capabilities of a purely instrumental setup to determine the potential of commonly used non-electrophilic
chemicals to cause skin sensitization by the generation of electrophilic species from the parent compound. In this work, the
electrophiles were generated by the electrochemical oxidation of aniline, a basic industrial chemical which may also be released
from azo dyes in cosmetics. The compound is a known sensitizer and was oxidized in an electrochemical thin-layer cell which
was coupled online to electrospray ionization–mass spectrometry. The electrochemical oxidation was performed on a boron-doped
diamond working electrode, which is able to generate hydroxyl radicals in aqueous solutions at high potentials. Without any
pretreatment, the oxidation products were identified by electrospray ionization/time-of-flight mass spectrometry (ESI-ToF-MS)
using their exact masses. A mass voltammogram was generated by plotting the obtained mass spectra against the applied potential.
Oligomerization states with up to six monomeric units in different redox states of aniline were observed using this setup.
This approach was extended to generate adducts between the oxidation products of aniline and the tripeptide glutathione. Two
adducts were identified with this trapping experiment. Protein modification was carried out subsequently: Aniline was oxidized
at a constant potential and was allowed to react with β-lactoglobulin A (β-LGA) or human serum albumin (HSA), respectively.
The generated adducts were analyzed by liquid chromatography coupled to ESI-ToF-MS. For both β-LGA and HSA, aniline adducts
were successfully generated and identified. |
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