Separation and aquatic toxicity of enantiomers of synthetic pyrethroid insecticides

Abstract

Synthetic pyrethroid insecticides are chiral compounds with multiple asymmetric positions. In this study, isomers of four commonly used pyrethroids were separated at the enantiomeric level by enantioselective high-performance liquid chromatography (HPLC), and differences between enantiomers in aquatic toxicity were characterized using individual isomers. Isomers of cis-bifenthrin and permethrin were completely resolved on a Sumichiral OA-2500-I column. All eight isomers of cypermethrin and cyfluthrin were completely separated on two chained Chirex 00G-3019-DO columns. Great differences were found between enantiomers in the acute toxicity to aquatic invertebrates Ceriodaphnia dubia or Daphnia magna. In cis-bifenthrin (cis-BF) and cis-permethrin (cis-PM), the 1R-cis isomer was 15-38 times more active than the 1S-cis enantiomer, while in trans-PM, the 1R-trans isomer was substantially more toxic than the 1S-trans enantiomer. In cypermethrin or cyfluthrin, two of the eight isomers, 1R-cis-alphaS and 1R-trans-alphaS, contributed for almost all the toxicity in the racemate, while the other six enantiomers were inactive. These results suggest that significant enantioselectivity occurs for pyrethroids in aquatic toxicity, and such enantiomeric differences must be considered when evaluating ecological effects of pyrethroid insecticides.

Synthetic Pyrethroid Use Patterns, Properties, and Environmental Effects

“…permethrin, Table III). In general the biological activity of different stereoisomers varies substantially (15)(16)(17)(18), so that enrichment of the most active isomer(s) yields a product with greatly enhanced insecticidal activity.. In recent years several isomerically enriched pyrethroid active ingredients have been introduced into commercial use.…”

Separation and aquatic toxicity of enantiomers of the organophosphorus insecticide trichloronate

“…A number of studies have shown that the potential biological effects such as toxicity, 2,3 endocrine disruption activity, 4 and environmental fate [5][6][7][8] of chiral pesticides are generally enantioselective. Therefore, it is imperative to assess the environmental safety of chiral OPs in their enantiopure forms.…”

Safety prediction of topically exposed biocides using permeability coefficients and the desquamation rate at the stratum corneum

“…The column temperature was increased from 50 to 170°C at 40°C/min, and then from 170 to 300°C at 6°C/min. Helium was selected as a carrier gas and selection ion monitoring (m/z of resmethrin; 123, 171) (Liu et al, 2005) was used as a detection method.…”