Interactions of the Bleaching Herbicide Clomazone with Reduced Glutathione and Other Thiols

The reactivity o f the bleaching herbicide clom azone with reduced glutathione (GSH) was studied under in vitro conditions. C lom azone at 1.3 m M and GSH a t 100 m M were reacted in a phosphate buffer (pH 8.8) at 25 CC for 3 days. The resulting synthetic product was identified as a G S-conjugate o f clom azone by means o f TLC , H PLC , and mass spectrom etry (chemical ionization) procedures. Exogenous application o f 0.5 m M o f G SH and cysteine reduced signifi­ cantly the bleaching effect o f clom azone on leaf disks o f velvetleaf (Abutilon theophrasti Medik.). M ercaptoethanol was no t effective in antagonizing the bleaching effect o f clom azone on velvetleaf leaf disks. These results show tha t clom azone can react with selected thiol com ­ pounds under in vitro conditions. The conjugation o f clom azone with GSH may be involved in the metabolic detoxication o f this herbicide in plants.