US EPA

3118284 

Journal Article 

Factors affecting the kinetics of disulfide bond reduction in hair 

Wickett, RR; Barman, BG 

1985 

0 

Journal of the Society of Cosmetic Chemists
ISSN: 0037-9832 

IPA/86/648056 

Soc 

REF 5 

75-86 

English 

IPA COPYRIGHT: ASHP The kinetics of hair disulfide bond reduction by dihydrolipoic acid (I) and its monothiol analogs, 8-thiooctanoic acid and thioglycolic acid, are compared as well as those of dithiothreitol (II), 1,3-dithio-2-propanol (1,3-dimercapto-2-propanol; III) and their derivatives, and 1,4-dithio-2-butanol (1,4-dimercapto-2-butanol; IV), using a single-fiber technique. Results show that I is many times faster in reducing hair than are its monothiol analogs correlating with the much higher equilibrium constant of the reaction between dithiol reducing agents and protein disulfide bonds. The reaction of a reducing agent with the hair disulfide bonds causes an increase in the diffusion constant of the reducing agent, affecting the overall reaction kinetics. 1,4-Dimercapto-2-butanol reduces disulfide bonds between 3 and 4 times as fast as II, the difference probably arising from different rates of diffusion into the hair, while IV only reduces hair about 25% faster than III. Structure-activity relationships in analogs of II and III illustrate the effects of hydroxyl groups on reactivity and differences between the formation of 5-membered dithiolane or 6-membered dithiane rings on oxidation. Results suggest that the efficacy of a variety of hair care products which act by reducing hair disulfide bonds may be affected by both the rate at which they react with the disulfide bonds and the ease with which they penetrate into the hair structure.