Metabolic Fate of Fthalide (4, 5, 6, 7-tetrachlorophthalide) in Compost

Fthalide, an effective fungicide for rice-blast, was easily degraded to water soluble compounds in a laboratory prepared compost. The following eighteen transient metabolites were identified in benzene extract and ethyl acetate extract of the compost treated with 14C-labeled fthalide at the lactone ring or the metabolites: 4, 5, 6-trichloro-, 4, 6, 7-trichloro-, 4, 6-dichloro-, 4, 7-dichloro-, 4-chloro-, 4, 5, 6-trichloro-7-methylthio- and 4, 6, 7-trichloro-5-methylthio-phthalide; tetrachloro-, 3, 4, 5-trichloro-, 3, 5, 6-trichloro-, 3, 5-dichloro-, 3, 6-dichloro-, 4, 5-dichloro-, 4-chloro-, 3, 5-dichloro-4-methylthio-, 4, 5-dichloro-3-methylthio- and 4-chloro-5-methylthio-phthalic acid; 3, 4, 5, 6-tetrachloro-2-hydroxymethylbenzoate. Metabolic pathways of fthalide were proposed. None of chlorinated benzoic acids were detected in the metabolites in spite of detailed investigation. Acute oral toxicity of the main metabolites to mammals was very low and phytotoxicity of them on vegitables in pre-emergence test was not so strong.