Intermediate Oxidation Products of Cystine in Oxidized Hair

Abstract

The disulfide-plus-thiol content and the "apparent thiol" content of altered and unaltered human hair have been determined by using both hydrolytic (colorimetric)a nd nonhydrolytic (polarographic) methods of analysis. Hair bleached with commercial cosmetic preparations, alkaline peroxide, and alkaline peracetate showed only small differences between the results obtained for the disulfide-plus-thiol contents obtained by the two analytical procedures. Furthermore, neither of these three bleaching systems yielded higher "apparent thiol" levels in bleached hair than in unbleached hair. These results suggest negligible quantities of cystine oxide residues as end products of these alkaline oxidations. In contrast, relatively large differences between hydrolytic and nonhydrolytic determinations of disulfide-plus-thiol contents and relatively large amounts of "apparent thiol" have been found in hair treated with aqueous solutions of acidic hydrogen peroxide or acidic peracetic acid. These results suggest cystine oxide residues as end products of these reactions, which implies oxidation of cystine by the —S—S— fission route rather than C—S fission.