SYNTHESIS, PROPERTIES, AND USE OF COPPER-CHELATING AMPHIPHILIC DITHIOCARBAMATES AS SYNERGISTS OF OXIDANT-GENERATING HERBICIDES

The effect of herbicides that act by generating active oxygen species is often mitigated by the enzymes of the Halliwell-Asada oxygen detoxi fication pathway. Use of compounds interfering with this pathway syner gizes herbicides, allowing the killing of weeds at lower herbicide dos es. We have used different dithiocarbamate chelators (Dtcs) capable of removing copper from superoxide dismutase, the first enzyme of the pa thway, suppressing its action. Dtcs with different hydrophilic-lipophi lic properties (sodium salts of ethyl (2-(2-ethoxyethoxy)ethyl)-, buty l (2-(2-ethoxyethoxy)ethyl) -, hexyl (2-(2-ethoxyethoxy)ethyl)-, and d ibutyldithiocarbamic acids) were synthesized so that they might penetr ate plant cuticles better than sodium diethyldithiocarbamate. Octanol- water distribution ratios and the stabilities of their copper complexe s were determined. All Dtcs tested had a high affinity for copper. The Dtcs did not prevent iron-catalyzed Fenton reaction leading to hydrox yl radical production in vitro. Therefore they would not protect plant s from the oxidative damage caused by herbicide, as do compounds that complex iron and thereby prevent the phytotoxic iron-catalyzed Fenton reaction. These amphiphilic compounds show some synergistic activity i n vivo, with paraquat as well as lactofen, herbicides that generate ac tive oxygen species by different mechanisms. The results demonstrate t hat dithiocarbamates have potential as synergists for oxidant-generati ng herbicides. (C) 1998 Academic Press.