Ascorbate radical levels in human sera and rat plasma intoxicated with paraquat and diquat.

To clarify the toxicological mechanism of action of paraquat and diquat, the level of ascorbate radical, an oxidized product of ascorbic acid, was examined using the electron spin resonance (ESR) method. The ascorbate radical level increased to twice the normal level in sera from humans acutely intoxicated with a 1:1 mixture of paraquat and diquat, and to more than 1.5 times the normal level in rat plasma containing moderate levels of paraquat. The dosage level for rats was 0.025% paraquat dichloride in the diet. The ascorbate radical in both intoxicated human sera and rat plasma decayed much faster than that in normal samples.