In vitro detoxification of soman in human plasma.

The degradation of soman in human plasma and at a physiological pH has been studied at the high nanomolar level. From a comparison between degradation of racemic soman in preincubated and unpreincubated plasma the concentration of phosphonylation sites was estimated at some 120 nM. The contribution of phosphonylation to the degradation of soman is eliminated by preincubation of the plasma with racemic soman. The rate constants of the total hydrolysis (enzymatic and nonenzymatic) were calculated from the semi-log plot of the degradation of C(+)- or C(-)-soman in preincubated plasma/Tris (50% v/v). The nonenzymatic part of the hydrolysis was estimated from experiments in plasma ultrafiltrate (100,000 NMWL)/Tris (50% v/v). The nonenzymatic contribution to the hydrolysis of the P(+)-isomers is negligible compared to the enzymatic hydrolysis.