Comparison of Phytotoxicities between 4-Fluorinated and Non-fluorinated 2-Chloro-5-(3, 4, 5, 6-tetrahydrophthalimido)benzoates

Protoporphyrinogen-IX oxidase inhibition and peroxidizing phytotoxicity were determined using a series of fluorinated and non-fluorinated alkyl 2-chloro-5-(3, 4, 5, 6-tetrahydrophthalimido)benzoates and their parent benzoic acid derivatives. Protoporphyrinogen-IX oxidase from corn etioplasts was extracted, and ethane formation by intact cells of the green algae Scenedesmus acutus was measured. The benzoates with a fluorine atom exhibited stronger peroxidizing phytotoxicity (higher ethane formation) than the benzoates having no fluorine atom although protoporphyrinogen-IX oxidase inhibition by the fluorinated analogues was found to be weaker or almost equal to the non-fluorinated analogues. These data strengthen and generalize our previous findings with cyclic imides having an N-(4-chloro-2-fluoro-5-carboxyphenyl) group. The fluorinated analogues, which are not necessarily stronger protoporphyrinogen-IX oxidase inhibitors, exhibit stronger peroxidizing phytotoxicity with intact plant cells than those without a fluorine atom.