Peroxidizing herbicides structures

Pierotti, C., Deal, C., and Derr, E. Activity coefficient and molecular structure, Ind. Chem. Eng. Fundam., 51 95-101, 1959. Pignatello, J.J. Dark and photoassisted Fe -catalyzed degradation of chlorophenoxy herbicides by hydrogen peroxide. Environ. 

The herbicidal activity of the bipyridyliums depends on their redox properties. Their abilities as one-electron acceptors of the right redox potential (-350 mV for diquat and -450 mV for paraquat) allow them to siphon electrons out of the photosynthetic electron-transport system, competing with the natural acceptors. The radical anion produced is then reoxidized by oxygen, generating the real toxicant, hydrogen peroxide, which damages plant cells. Structure-activity relationships in this series have been reviewed (60MI10701). 

In addition lipid peroxidation can result from action of active oxygen species. This leads to destruction of metabolically necessary lipid molecules and damage to the structural integrity of cellular membranes. Damage from oxidative stress can occur with excessive production of active oxygen species, inadequate protection against such species, or both. Examples of toxicity from active oxygen species include the pancreatic beta-cell destruction by alloxan, the neurotoxicity of 6-hydroxydopamine, the cardiotoxicity of the anthracy-cline antibiotics, and the pulmonary toxicity of the herbicide paraquat. 

Table 5.2 shows examples of the major NDPE herbicides, and Figure 5.8 shows examples of other classes of miscellaneous herbicides whose mode of action has been considered identical to that of NDPEs based on their similar symptomology. The typical symptoms of these compounds are similar to those of paraquat. They cause a light-dependent, rapid chlorosis and necrosis due to a rapid induction of peroxidative degradation of cellular constituents, particularly membrane lipids. Several ultrastructural studies have revealed that the NDPEs and other compounds (oxadiazon, LS 82-556, M B 39279) show distinct differences in the sequence of ultra-structural damage compared to that induced by paraquat. ... 

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