N,N-dichlorotaurine: chemical and bactericidal properties.

The biogenous antimicrobial agent N-chlorotaurine (NCT) converts by disproportionation to N,N-dichlorotaurine (NDCT) at a rate proportional to acidity. This occurs at appreciable amounts already in weakly acidic biological systems. To understand the consequences of NDCT formation, a thorough investigation of this undescribed compound was mandatory, which needed its synthesis. Differently from NCT, this was possible in the aqueous system using trichloroisocyanuric acid. While the free acid, Cl(2)HNCH(2)CH(2)SO(3)H, was not available in pure form, its sodium and potassium salts were analytically pure and showed melting points (decomposition) of 125-128 degrees C (potassium) and 162-164 degrees C (sodium). The sodium salt demonstrated unexpected long-term stability even at room temperature (8.4 % loss of activity within 4 months). The aqueous solutions of both salts exhibited a weak acid reaction, and they were less stable than NCT. With regard to chlorination of amines (transhalogenation), NDCT was, surprisingly, less efficacious than NCT, which manifested itself by a lack of reactivity at pH < 7, for which a mechanistic explanation is given. Compared on a molar scale, NDCT was more bactericidal than NCT against the gram-negative bacteria E. coli, P. aeruginosa and P. mirabilis, while there was no difference concerning the gram-positive ones, S. aureus and S. epidermidis. The increase of bactericidal activity at acidic pH was the same as observed with NCT and is attributed to a higher susceptibility of bacteria in this environment. Taken together, NDCT seems not to be suited to substitute NCT as a preparation fit for medical practice.