Enantioselective Bioconcentration Behavior And Toxicity Of Typical Chiral Triazole Fungicide In The Zebrafish(Danio Rerio)

Triazole fungicides are the most widely used fungicides in the world. Approximately,84% of triazole fungicides are chiral. And most of triazole fungicides are marketed and used in the form of racemates. Chiral pesticide enantiomers often show significant different bioactivity to the target organisms, toxicity to non-target organisms, and accumulation in animals and plants after entering an ecological environment. However, the differences of chiral pesticide enantiomers are often ignored in the traditional risk assessment and the obtained assessment data are often unreliable, which may cause many potential threats to public health and environmental safety. Tebuconazole, uniconazole and epoxiconazole are the most widely sold fungicides in the world and widely used on agricultural crops. However, there is little data about bioconcentration and toxicity of tebuconazole, uniconazole and epoxiconazole at an enantiomeric level. It will bring the potential risk to the safety evaluation of pesticide.Firstly, a simple and sensitive method for the enantioselective determination of tebuconazole enantiomers in water and zebrafish has been established using ultra performance convergence chromatography tandem mass spectrometry (UPCC-MS/MS). The effects of the chiral stationary phases, mobile phase, auto back pressure regulator pressure, column temperature, flow rate of the mobile phase and compensation pump solvent were evaluated. The modified QuEChERS method was applied to water and zebrafish samples.Secondly, the acute toxicity of rac-tebuconazole, rac-uniconazole and rac-epoxiconazole to zebrafish were tested. The results indicated that the LCso-96h 96 h LC50 for tebuconazole,uniconazole and epoxiconazole were 10.74 mg/L,11.57 mg/L and 9.60 mg/L, respectively.Thirdly, the enantioselective bioconcentration behavior of tebuconazole, uniconazole and epoxiconazole in zebrafish(Danio rerio) were investigated, respectively. A significant trend in enantioselective bioconcentration were observed in these zebrafish with the preferential accumulation of (-)-R-tebuconazole, (+)-S-uniconazole and (+)-epoxiconazole at two dose levels, respectively. The results of the depuration experiments indicated that the degradation of (-)-R-tebuconazole, (+)-S-uniconazole and (+)-epoxiconazole in zebrafish were slower than these enantiomers. The degradation of these enantiomers in zebrafish were rapid.Finally, the effect of antioxidant system of rac-tebuconazole,rac-epoxiconazoleand their enantiomers in zebrafish were studied.The results indicated there were enantiomer differences in enzyme activity of POD、SOD and GSH-Px in zebrafish. The results showed that rac-tebuconazole, rac-epoxiconazole and their enantiomers inhibit the activity of POD and SOD,and activate the activity of GSH-Px.The results of the present study provide support for minimizing the risk of tebuconazole, uniconazole and epoxiconazole to humans, animals and ecosystems.