MEASUREMENT OF THE STABILITY OF T-2 TOXIN IN AQUEOUS-SOLUTION

Studies were undertaken to determine unambiguously the stability of T- 2 toxin in deuterated phosphate-buffered saline solutions in the pD ra nge 5-12. No decomposition was observed after 1 year in samples betwee n pD 5.0 and 6.7; above pD 6.7, degradation proceeded via sequential c leavage of the ester side chains to form the series HT-2 toxin to T-2 triol to T-2 tetraol. A transient species believed to be an internal t ransesterification product of T-2 triol was also detected. Proton NMR was found to be a finely discriminatory technique for the observation and characterization of these species. It was possible for the first t ime to observe ''in real time'' the mixture of species, to model the m ultistage kinetics involved in their interconversion, and to obtain a set of rate constants. The kinetics of the breakdown of T-2 toxin at p D 11.2 were investigated. All reactions were found to be pseudo-first- order with half-lives of 5.4 and 11.7 h for T-2 toxin and HT-2 toxin, respectively. By extrapolation of these results, the half-life of T-2 toxin under quasi-physiological conditions (pD 7.4) was estimated to b e about 4 years: this estimate is in broad agreement with the behavior observed in the stability study. Given this remarkable stability of T -2 toxin under pseudophysiological conditions, it was concluded that t he contribution of nonenzymatic degradation to the detoxification of T -2 toxin and its metabolites is almost certainly negligible.