Chiral fungicide penconazole: absolute configuration, stereoselective bioactivity, toxicity, and environmental behavior in apple
Chiral pesticides are existing two mirror images called enantiomers. In spite of their similar elements and structures, enantiomers of chiral pesticides were reported that could have different environmental behavior, bioactivities, toxicities, and metabolic characteristics when exposure of them to nature. Penconazole is a systemic fungicide of the triazole family. Up to now, the absolute configuration is undetermined. The bioactivity and toxicity of penconazole at stereomeric level have not been reported. In the present study, the analysis method of penconazole enantiomers by UPLC-MS/MS was optimized and a rapid quantitative analytical method was established. The work down systematically explored the absolute configuration, bioactivity, ecotoxicity, and environmental behavior of chiral fungicide penconazole. The absolute configuration of penconazole was confirmed by electronic circular dichroism (ECD). The acute toxicity toward Daphnia magna (Daphnia magnastraus). The enantioselective biological activities of penconazole enantiomers and raceme against four target pathogenic fungi, Alternaria alternate, Botryosphaeria dothidea, Colletotrichum gloeosporioides and Fusarium oxysporum. Stereoselective degradation test of penconazole in apple was conducted with bagging and non-bagging treatment among three regions in China. This results are expected to promote penconazole enantiomers application to improve pesticide effectiveness and to alleviate environmental pollution. And More accurate risk assessment will be analyzed to guarantee food security. The two stereoisomers of penconazole were separated by UPLC-MS/MS system with a Lux Cellulose-2 column (150 mm ×4.6 mm, 5 μm). 0.1% formic acid in methanol and 10 mmol/L ammonium acetate in water as the mobile phase. The effectiveness of the mobile phase ratios, column temperatures and flow rates were evaluated. The mobile phase A/B: 80/20, column temperature: 30 °C, flow rate: 0.25 ml/min were eventually chosen. The retention time of penconazole stereoisomers was about 8 min, less than half of previous detection time, and the RS was 1.75 indicating completely separation of penconazole stereoisomers. The absolute configuration of penconazole stereoisomers was confirmed by comparing experimental circular dichroism (CD) spectra with theoretical electronic circular dichroism (ECD) spectra. The three apple-producing areas in China (Liaoning province, Shandong province, Shanxi province) were picked on as open filed location. The fungicidal activity of penconazole and its stereoisomers were evaluated toward four target pathogens: Alternaria alternate, Botryosphaeria dothidea, Colletotrichum gloeosporioides and Fusarium oxysporum, which were cultivated in PDA medium. The acute toxicity tests of rac-penconazole and its two stereoisomers were carried out with Daphnia magna under the Test guidelines on environmental safety assessment for chemical pesticides: Daphnia magna acute immobilization test.