title: Tyrosinase-mediated cytotoxicity of 4-substituted phenols: quantitative structure-thiol-reactivity relationships of the derived o-quinones.
abstract: Rate constants have been determined for reactions between biologically significant thiols, represented by cysteine and glutathione, and a series of 10 4-substituted o-quinones, and unsubstituted o-quinone itself, generated by rapid disproportionation of the semiquinones formed from the corresponding catechols by pulse radiolysis. The quantitative structure-reactivity relationships were investigated by examining the correlation between the rate constants and various Hammett and other parameters characterizing the electronic nature of the substituents. From these relationships, it can be concluded that the o-quinone reactivity with thiols increases with the electron-withdrawing capacity of the substituent groups and that this effect is principally due to resonance effects. Such relationships allow the prediction of likely reactivities with cellular thiols of further o-quinones whose 4-substituents have known electronic parameters. These reactivities are likely to be one of the critical factors determining overall cytotoxicity, assisting in the choice of improved melanogenesis-targeted anti-melanoma drugs.
authors.affiliation: Department of Chemistry, University College London, UK.
authors.forename: C J
authors.initials: CJ
authors.lastname: Cooksey
authors.forename: E J
authors.initials: EJ
authors.lastname: Land
authors.forename: C A
authors.initials: CA
authors.lastname: Ramsden
authors.forename: P A
authors.initials: PA
authors.lastname: Riley
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry* / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D003545:Cysteine / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry; D007700:Kinetics; D008545:Melanoma / Q000188:drug therapy / Q000473:pathology; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010636:Phenols / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D011809:Quinones / Q000737:chemistry* / Q000494:pharmacology; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D010636:Phenols; D011809:Quinones; D014442:Monophenol Monooxygenase; D005978:Glutathione; D003545:Cysteine