title: Photolysis of the herbicide sulcotrione: formation of a major photoproduct and its toxicity evaluation.
abstract: BACKGROUND
  Sulcotrione is a selective herbicide marketed for use in maize since 1993, but its environmental fate is not yet fully elucidated. A major metabolite resulting from cleavage between the two ring moieties, leading to 2-chloro-4-mesylbenzoic acid (CMBA), has been identified; it presents a rather low toxicity. In photochemical studies this compound has also been claimed to be formed in high proportions. The present authors recently found that, under irradiation, sulcotrione mainly yields a cyclization product (CP). Thus, Sulcotrione photochemistry is still a matter of debate. The aim of the present work was to give an unequivocal answer to this issue. The potential toxicity of CP, CMBA and sulcotrione towards three organisms considered as representative of aquatic ecosystems was also evaluated.
  
  
  RESULTS
  The main transformation product of sulcotrione is the cyclization product (CP), and CMBA is formed in smaller amounts. For the toxicological approach, the tested organisms were a bacterium, Vibrio fischeri (Bejerinck) Lehmann & Neumann, an alga, Pseudokirchneriella subcapitata (Korshikov) Hindak, and a protozoan, Tetrahymena pyriformis (Ehrenberg) Lwoff. Sulcotrione is more harmful towards the alga, but CP is more toxic to the bacterium and the protozoan. It must be noted that the measured toxicities are nonetheless rather low.
  
  
  CONCLUSIONS
  On irradiation, sulcotrione mainly gives the photocyclization product, which presents a higher toxicity than sulcotrione and CMBA. This cyclization product should thus be considered in sulcotrione environmental risk assessment.
authors.affiliation: Laboratoire de Photochimie Moléculaire et Macromoléculaire, UMR CNRS-UBP 6505, Université Blaise-Pascal, Aubière Cedex, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: ter Halle
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Wiszniowski
authors.forename: Adnane
authors.initials: A
authors.lastname: Hitmi
authors.forename: Gérand
authors.initials: G
authors.lastname: Ledoigt
authors.forename: Frédérique
authors.initials: F
authors.lastname: Bonnemoy
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Bonnet
authors.forename: Jacques
authors.initials: J
authors.lastname: Bohatier
authors.forename: Claire
authors.initials: C
authors.lastname: Richard
mesh_terms: D000818:Animals; D001419:Bacteria / Q000187:drug effects; D003512:Cyclohexanones / Q000737:chemistry*; D056890:Eukaryota / Q000187:drug effects; D008698:Mesylates / Q000737:chemistry*; D015394:Molecular Structure; D010782:Photolysis; D013769:Tetrahymena pyriformis / Q000187:drug effects; D018675:Toxicity Tests
chemical_list: D003512:Cyclohexanones; D008698:Mesylates; C079906:sulcotrione