Regiospecific Attack of Nitrogen and Sulfur Nucleophiles on Quinones Derived from Poison Oak/Ivy Catechols (Urushiols) and Analogues as a Models for Urushiol-Protein Conjugate Formation

Attempts to characterize potential biologically important covalent interactions between electrophilic quinones derived from catechols present in poison oak / ivy (urushiol) and biomacromolecules have led to the analysis of madel reactions involving sulfur and amoni uncleophiles with 3-feptadecylbenzoquinone.Characterization of the reaction products indicates that this quinone undergoes regiospcific attack by (S)-N-acetylcysteine at C-6 and by 1-aminopentane at C-5. The red solid obtained with 1-aminopentane proved to be 3-heptadecyl-5 (pentylamino) -1, 2-benzoquinone. Analogous aminobenzoquinones were obtained with the quinones derved from the 4-and 6-methyl analogues of 3-pentadecycatechol. All three adducts absorbed light at different wavelengths. When the starting catechols were incubated with human serum albumin almost identical chromophores were formed. These results establish that catechols responsible for the production of the poison oak / ivy contact dermatitis in humans undergo a sequence of reactions in the presence of human serum albumin that lead to covalent attachment of the catechols to the protein via carbon-introgen bonds. Estimations of the extent of this binding indicate that, at last with human serum albumin, the reaction is quantitative.