Safening efficacy of halogenated acetals, ketals and amides and relationship between the structure and effect on glutathione and glutathione S-transferases in maize

Halogenated acetal, ketal and acetamide type molecules were synthesized and tested for their ability to alleviate toxicity of acetochlor to maize and differentially enhance the glutathione (GSH) content and glutathione S-transferase (GST) activity in shoots and roots of maize. Safening experiments revealed that the dichloroacetals were inactive, while dichloroketals were effective as safeners. The degree of induction of GSH levels and GST activity measured with CDNB and acetochlor substrates were not correlated with the protective effects observed. Since both the herbicide and the experimental safeners, as chemical stressors, induce specific GST activities, we can conclude that increased GST activities are not solely responsible for the safening effect. The protective efficacy of dichloroketal safeners does not seem to be associated with enhanced herbicide detoxication by glutathione conjugation.