INVITRO CONJUGATION OF GLUTATHIONE AND OTHER THIOLS WITH ACETANILIDE HERBICIDES AND EPTC SULFOXIDE AND THE ACTION OF THE HERBICIDE ANTIDOTE R-25788

Nonenzymatic reaction in vitro of 3H-labeled glutathione (GSH) with [14C]alachlor, [14C]metolachlor, [14C]H-22234, and [14C]EPTC sulfoxide formed dual-labeled GSH-herbicide conjugates. GSH did not conjugate in this system with the herbicides buthidazole, atrazine, EPTC, or the herbicide antidote R-25788. Alachlor also conjugated with the thiol-containing compounds cysteine, dithiothreitol, and coenzyme A but not with methionine, acetyl-CoA, mercaptoethanol, or ethanethiol. The alachlor-GSH conjugation reaction yielded more product with increased pH (over pH 6.0), indicating that the in vitro reaction proceeds by way of the GS- ion. Although the GSH-acetanilide conjugation reaction had a low yield at physiological pH, it could be the basis for the protection of corn from acetanilide herbicide injury by R-25788. It is suggested that R-25788 may protect corn from EPTC injury by increasing the rate of EPTC sulfoxidation, followed by subsequent EPTC sulfoxide-GSH conjugation. © 1979, American Chemical Society. All rights reserved.