Evaluation of exploitive potential for higher bioactivity and lower residue risk enantiomer of chiral fungicide pydiflumetofen.

Background Pydiflumetofen, as a new succinate dehydrogenase inhibitor (SDHI) chiral fungicide, has been used in crop production because of its broad-spectrum and high-efficiency antifungal activity. However, little literature is known about pydiflumetofen at the chiral level. Therefore, the stereoselective bioactivity and degradation of pydiflumetofen enantiomers were investigated. Results Pydiflumetofen presented effective bioactivity against the eight tested phytopathogens, and its enantiomers showed significant difference in activity. The bioactivity of R-pydiflumetofen was 9.0 ~ 958.8 times higher than that of S-enantiomer. Treatment with R-pydiflumetofen increased the cell membrane permeability of Sclerotinia sclerotiorum and decreased more exopolysaccharide and oxalic acid production more than treatment with S-pydiflumetofen. Furthermore, R-pydflumetofen exhibited better inhibitory activity against the succinate dehydrogenase (SDH) enzyme of S. sclerotiorum than S-pydiflumetofen by 584-folds. According to homology modeling and molecular docking studies, the binding affinities of the R-enantiomer and S-enantiomer were - 7.0 kcal mol-1 and -5.3 kcal mol-1 , respectively. Additionally, the degradation half-lives of S- and R-pydiflumetofen in three vegetables (cucumber, eggplant, and cowpea) under field conditions were 2.56 ~ 3.12 d and 2.48 ~ 2.76 d, respectively, which revealed that R-pydiflumetofen degraded faster than S-pydiflumetofen. Conclusion Based on the results obtained, R-pydiflumetofen not only exhibited a higher bactericidal activity, but also posed fewer residual risks in the environment. The mechanism of the stereoselective bioactivity was correlated with the stereoselective inhibition activity of the target enzyme and then effected the cell membrane permeability and the production of exopolysaccharide and oxalic acid. This research could provide a foundation for the systematic evaluation of pydiflumetofen from an enantiomeric view. This article is protected by copyright. All rights reserved.