Wang Yei-Shung, Tai Kok-Thong, Yen Jui-Hung
Department of Agricultural Chemistry, National Taiwan University, 1, Sec 4, Roosevelt Road, Taipei 10617, Taiwan.
Ecotoxicol Environ Saf. 2004 Mar;57(3):346-53. doi: 10.1016/j.ecoenv.2003.08.012.
Most chiral pesticides are used as racemates despite the fact that the pesticidal activity of the given pesticide is usually the result of the preferential reactivity of only one enantiomer while the other enantiomers may have toxic effects against other nontarget organisms. Accordingly, the enantiomer of fenamiphos, an organophosphorus pesticide, was separated by high-performance liquid chromatography with reverse phase and normal phase on a Pirkle model chiral stationary phase column. It was found that n-hexane/isopropanol (95/5) was the best solvent system for enantiomer resolution of fenamiphos. Chromatographic data including capacity factor (k'), separation factor (alpha), and resolution (Rs) are presented. Inhibitory activity to enzyme butyrylcholinesterase and toxicity to Daphnia of enantiomers and racemic insecticide fenamiphos were also studied. In the toxicity tests of Daphnia, the lethal concentration (LC50) of (+)-fenamiphos, (-)-fenamiphos, and racemate were 0.0016, 0.0061, and 0.0019 microg/mL, respectively. No significant difference of LC50 values between (+)-fenamiphos and racemate were found, but (-)-fenamiphos showed significantly lower toxicity to Daphnia. The inhibitory concentration (IC50) to the cholinesterase were 0.008, 0.15, and 0.46 microg/mL for (+)-fenamiphos, (-)-fenamiphos, and racemate, respectively. Both enantiomers and the racemate showed significant difference in inhibiting the cholinesterase. However, (+)-fenamiphos proved to be about 20 times more toxic to Daphnia and only about four times more inhibitory activity to butyrylcholinesterase than (-)-fenamiphos. The dissipation of (+)-fenamiphos, (-)-fenamiphos, and racemate in selected soils and natural water samples were also studied. The half-life (t(1/2)) of (+)-, (-)-, and racemate in soils showed no related to the soil texture, pH, or organic carbon content. By comparing the residues of (+)-, (-)-, and racemate in the water, it was found that (+)-fenamiphos was degraded faster than the others after 21 days. Briefly, (+)-fenamiphos is more toxic than (-)-fenamiphos to a nontarget organism (Daphnia), but the environmental persistence of the two compounds showed no significant difference.
尽管大多数手性农药的杀虫活性通常仅由一种对映体的优先反应性导致，而其他对映体可能对其他非靶标生物具有毒性作用，但大多数手性农药仍以消旋体形式使用。因此，采用高效液相色谱法，在Pirkle型手性固定相柱上，通过反相和正相分离了有机磷农药苯线磷的对映体。发现正己烷/异丙醇（95/5）是分离苯线磷对映体的最佳溶剂体系。给出了包括容量因子（k'）、分离因子（α）和分离度（Rs）在内的色谱数据。还研究了对映体和外消旋杀虫剂苯线磷对丁酰胆碱酯酶的抑制活性以及对水蚤的毒性。在水蚤毒性试验中，（+）-苯线磷、（-）-苯线磷和外消旋体的致死浓度（LC50）分别为0.0016、0.0061和0.0019μg/mL。（+）-苯线磷和外消旋体的LC50值之间未发现显著差异，但（-）-苯线磷对水蚤的毒性显著较低。（+）-苯线磷、（-）-苯线磷和外消旋体对胆碱酯酶的抑制浓度（IC50）分别为0.008、0.15和0.46μg/mL。两种对映体和外消旋体在抑制胆碱酯酶方面均表现出显著差异。然而，（+）-苯线磷对水蚤的毒性比（-）-苯线磷高约20倍，对丁酰胆碱酯酶的抑制活性仅比（-）-苯线磷高约四倍。还研究了（+）-苯线磷、（-）-苯线磷和外消旋体在选定土壤和天然水样中的消散情况。（+）-、（-）-和外消旋体在土壤中的半衰期（t(1/2)）与土壤质地、pH值或有机碳含量无关。通过比较水中（+）-、（-）-和外消旋体的残留量，发现21天后（+）-苯线磷的降解速度比其他物质快。简而言之，（+）-苯线磷对非靶标生物（水蚤）的毒性比（-）-苯线磷大，但两种化合物在环境中的持久性没有显著差异。
