Jones W Jack, Mazur Christopher S, Kenneke John F, Garrison A Wayne
Ecosystems Research Division, National Exposure Research Laboratory, U.S. Environmental Protection Agency, 960 College Station Rd., Athens, Georgia 30605, USA.
Environ Sci Technol. 2007 Dec 15;41(24):8301-7. doi: 10.1021/es071409s.
Fipronil, a chiral insecticide, was biotransformed initially to fipronil sulfide in anoxic sediment slurries following a short lag period. Sulfidogenic or methanogenic sediments transformed fipronil with half-lives of approximately 35 and 40 days, respectively. In all microbially active sediment slurries tested, the transformation of fipronil to fipronil sulfide was enantioselective. In the sulfidogenic sediment slurry, the enantiomeric fraction (EF) of fipronil decreased from an initial racemic EF value of 0.46 to a value of 0.22 during the incubation period of active fipronil transformation, indicating preferential transformation of the S-(+)-enantiomer. A previously unidentified product, 5-amino1-[2,6-dichloro-4-(trifluoromethyl)-phenyl]-4-(trifluoromethylthio)-1-H-pyrazole-3-carboxyamide, or fipronil sulfide-amide, was detected in the sulfidogenic slurries and coincided with the loss of fipronil sulfide. Biota from methanogenic freshwater sediment slurries also transformed fipronil enantioselectively but with a preference for the R-(-)-enantiomer. In all microbially inhibited (autoclaved) sediment slurries tested, no changes in the enantiomeric fractions of fipronil were observed and only low levels (< 5% of the added fipronil) of the fipronil sulfide metabolite were detected. In defined (model) chemical experiments, solutions of pyrite (FeS2) and iron sulfide (FeS) non-enantioselectively transformed fipronil primarily to either 2,6-dichloro-4-(trifluoromethyl)-aniline or to fipronil sulfide and fipronil amide, respectively. This report provides the first experimental evidence of enantioselective microbial transformation of fipronil in a natural environment (soil, water, and sediment) as well as identification of a novel fipronil biotransformation product.
氟虫腈是一种手性杀虫剂，在缺氧的沉积物泥浆中经过短暂的滞后期后，最初会生物转化为氟虫腈硫化物。产硫化物或产甲烷的沉积物对氟虫腈的转化半衰期分别约为35天和40天。在所有测试的具有微生物活性的沉积物泥浆中，氟虫腈向氟虫腈硫化物的转化具有对映体选择性。在产硫化物的沉积物泥浆中，在氟虫腈活跃转化的培养期内，氟虫腈的对映体分数（EF）从初始外消旋EF值0.46降至0.22，表明S-(+)-对映体优先转化。在产硫化物的泥浆中检测到一种先前未鉴定的产物，5-氨基-1-[2,6-二氯-4-(三氟甲基)-苯基]-4-(三氟甲硫基)-1-H-吡唑-3-甲酰胺，即氟虫腈硫化物-酰胺，它与氟虫腈硫化物的损失同时出现。来自产甲烷淡水沉积物泥浆中的生物群也对氟虫腈进行对映体选择性转化，但更倾向于R-(-)-对映体。在所有测试的微生物抑制（高压灭菌）沉积物泥浆中，未观察到氟虫腈对映体分数的变化，仅检测到低水平（<添加氟虫腈的5%）的氟虫腈硫化物代谢物。在特定（模型）化学实验中，黄铁矿（FeS₂）和硫化铁（FeS）溶液分别将氟虫腈非对映体选择性地主要转化为2,6-二氯-4-(三氟甲基)-苯胺或氟虫腈硫化物和氟虫腈酰胺。本报告提供了氟虫腈在自然环境（土壤、水和沉积物）中对映体选择性微生物转化的首个实验证据，以及一种新型氟虫腈生物转化产物的鉴定。
