Hainzl D, Casida J E
Department of Environmental Science, Policy, and Management, University of California, Berkeley 94720-3112, USA.
Proc Natl Acad Sci U S A. 1996 Nov 12;93(23):12764-7. doi: 10.1073/pnas.93.23.12764.
Fipronil is an outstanding new insecticide for crop protection with good selectivity between insects and mammals. The insecticidal action involves blocking the lambda-aminobutyric acid-gated chloride channel with much greater sensitivity of this target in insects than in mammals. Fipronil contains a trifluoromethylsulfinyl moiety that is unique among the agrochemicals and therefore presumably important in its outstanding performance. We find that this substituent unexpectedly undergoes a novel and facile photoextrusion reaction on plants upon exposure to sunlight, yielding the corresponding trifluoromethylpyrazole, i.e., the desulfinyl derivative. The persistence of this photoproduct and its high neuroactivity, resulting from blocking the lambda-aminobutyric acid-gated chloride channel, suggest that it may be a significant contributor to the effectiveness of fipronil. In addition, desulfinylfipronil is not a metabolite in mammals, so the safety evaluations must take into account not only the parent compound but also this completely new environmental product.
氟虫腈是一种用于作物保护的新型高效杀虫剂，对昆虫和哺乳动物具有良好的选择性。其杀虫作用是通过阻断γ-氨基丁酸门控氯离子通道实现的，该靶点在昆虫体内的敏感性远高于哺乳动物。氟虫腈含有一个三氟甲基亚磺酰基部分，这在农用化学品中是独一无二的，因此可能是其卓越性能的重要原因。我们发现，该取代基在植物暴露于阳光时会意外地发生一种新颖且容易的光脱除反应，生成相应的三氟甲基吡唑，即脱亚磺酰基衍生物。这种光产物的持久性及其通过阻断γ-氨基丁酸门控氯离子通道产生的高神经活性表明，它可能是氟虫腈有效性的重要贡献者。此外，脱亚磺酰基氟虫腈在哺乳动物体内不是代谢产物，因此安全性评估不仅必须考虑母体化合物，还必须考虑这种全新的环境产物。
