What are triclocarban and triclosan (ingredients in some antiseptic soaps)?

	Vocabulary
	active site enzyme fatty acid

Triclocarban. Click on the structures for a 3D Chime molecular model.

Triclosan. Click on the structures for a 3D Chime molecular model.

Triclosan and triclocarban have been used as effective antiseptics [1] in soap since the 1960's. Triclosan has been incorporated into a wide range of consumer goods, including cosmetics, toothpaste, and plastics for children's toys and kitchen and table utensils.

Neither substance is very soluble in water, but both are fat-soluble and easily cross cell membranes. Once inside the cell, triclosan poisons a specific enzyme that many bacteria and funguses need for survival [2,3]. Triclosan blocks the active site of an enzyme called enoyl-acyl carrier-protein reductase (ENR for short), preventing the bacteria from manufacturing fatty acids it needs for building cell membranes and other vital functions. Humans don't have this enzyme, so triclosan is harmless to them. One molecule of triclosan permanently disables an ENR molecule, which explains why triclosan has powerful antibiotic action even at very low concentrations. Triclocarban's structural similiarity suggests a similiar mode of action.

The highly specific way that triclosan kills has researchers concerned about its role in fostering antibiotic-resistant strains of bacteria [2]. Researchers have recently demonstrated that mutations in the bacterial gene that produces ENR can produce triclosan-resistant bacteria. Because triclosan is now so widespread in the environment, it's likely that new antibiotics targeting ENR would be ineffective.

References

1. Yackovich, F., N. K. Poulsen, and J. E. Heinze, "Validation of the Agar Patch Test Using Soap Bars which Deposit Different Amounts of Triclocarban", J. Soc. Cosmet. Chem., 37: 99-104 (1986).
2. McMurray, L. M., Oethinger, M, Levy, S. B., "Triclosan targets lipid synthesis", Nature 394, 531-32 (1998). Abstract
3. Levy, C. W., Roujeinikovai, A., Sedelnikova, S., Baker, P. J., Stuitje, A. R., Slabas, A. R., Rice, D., & Rafferty, J. B., "Molecular Basis of Triclosan Activity", Nature, 398, 383-384 (1999). Abstract
4. Triclocarban, National Toxicology Program Chemical Repository Data Sheet (Radian Corporation, August 29, 1991), National Institute of Health, USA. WWW: http://ntp-server.niehs.nih.gov/.
5. Triclocarban, BIAM (Automated Drug Databank), WWW: http://www.biam2.org/www/Sub3342.html

Related Web Links

Soaps and Detergents (Soap & Detergent Association)

A general explanation of the detergent terminology, including a table showing the function of each ingredient in common cleaning products. An illustrated introduction to soap chemistry is included elsewhere on the site. http://www.sdahq.org/sdalatest/html/soapproducts1.htm (6/27/99)

Author: Fred Senese senese@antoine.frostburg.edu