2-iso-Propylphenyl N-methylcarbamate(ミプシン^[○!R], MIPC)の水稲における代謝と土壌中における分解 Metabolism of 2-iso-Propylphenyl N-Methylcarbamate (Mipcin^[○!R], MIPC) in Rice Plants and Its Degradation in Soils

殺虫剤, 2-iso-propylphenyl N-methylcarbamate(ミプシン^[○!R], MIPC)の側鎖のmethyl基を^<14>Cで標識した化合物を用いて, 水稲における吸収, 移行と代謝, および土壌中における分解を検討した.水稲では, ^<14>C-ミプシンは根や葉面から吸収され, 上部または他の葉へ移行するが, おもに揮散により消失し, 収穫時の残留量は少なかった.稲体内に吸収されたミプシンは代謝されて, 稲わら中ではおもに, 2-(1-hydroxy 1-methylethyl)phenyl N-methylcarbamateと2-iso-propylphenyl N-hydroxymethylcarbamateが生成し, 玄米中ではおもに, その水抽出物を加水分解することにより2-iso-propylphenylcarbamateが認められた.土壌では, 湛水条件下よりも畑地条件下で分解が速く, それぞれおもに, 2-iso-propylphenolと2-iso-propylphenylcarbamateを生成した.ミプシンの代謝物の生物学的評価を3種のコリンエステラーゼの阻害度から検討した結果, ほとんどの代謝物や分解物はミプシンよりも阻害度が低かった.

Absorption, translocation, and metabolism of 2-iso-propylphenyl N-methylcarbamate (Mipcin^[○!R], MIPC) in rice plants and its degradation in soils were studied by using ^<14>C-Mipcin labeled at methyl of iso-propyl group of ring substituted side chain. ^<14>C-Mipcin was absorbed easily from roots and leaves of rice plants, translocated to upper parts, and was lost from leaves. As predominant metabolites in straw, 2-(1-hydroxy 1-methylethyl)phenyl N-methylcarbamate and 2-iso-propylphenyl N-hydroxymethylcarbamate were detected. In grain, conjugated metabolites which were hydrolyzed to 2-iso-propylphenylcarbamate by HCl were observed. Degradation of Mipcin in soils was more rapid under upland conditions than under flooded conditions. The main degradation products were 2-iso-propylphenylcarbamate under upland conditions and 2-iso-propylphenol under flooded conditions. Most of these metabolites were found to be less toxic than the parent compound with respect to the inhibitory activity on cholinesterase.