Systemic assessment of the chiral insecticide pyriproxyfen in a citrus nectar source system: Stereoselective degradation, biological effect and exposure risk

Abstract

BACKGROUND: Balancing the safety and efficiency of chiral pesticides can help protect pollinators. We evaluated the stereoselective behavior, bioactivity, toxicity and exposure risk of the chiral insecticide pyriproxyfen in a citrus nectar system. RESULTS: Density functional theory (DFT) and ultra-performance liquid chromatography tandem mass spectroscopy (UPLC-MS/ MS) were applied for absolute configuration appraisal and chiral analysis validation, respectively. The recoveries ranged from 72.3% to 100.5% with an relative standard deviation (RSD) ranging from 1.2% to 9.7%. In a field trial, we determined insecticide half-lives in citrus leaves and flowers, which were 7.0 and 8.6 days for R-(+)-pyriproxyfen, and 11.7 and 14.7 days for S-(−)-pyriproxyfen, respectively. We found that the bioactivity of R-(+)-pyriproxyfen was 3.39 and 2.37 times higher than S-(−)-pyriproxyfen against Unaspis yanonensis and Diaphorina citri nymphs, respectively. S-(−)-pyriproxyfen had 3.8 times higher acute toxicity than R-(+)-pyriproxyfen on Apis mellifera L., and its exposure risk was moderate based on the hazard quotient.CONCLUSION: The phenomenon of stereoselective degradation and biological effect demonstrated that the high-risk stereoisomer of S-(−)-pyriproxyfen degraded more slowly than R-(+)-pyriproxyfen, but R-(+)-pyriproxyfen with better efficiency for target. Therefore, an increased duration of R-(+)-pyriproxyfen activity on citrus was beneficial for efficacy. Our results could guide the scientific application and evaluation of chiral pesticides on nectar plants.

Chiral Herbicide Fluorochloridone: Absolute Configuration, Stereoselective Bioactivity, Toxicity, and Degradation in the Potatoes

“…The crystal belonged to an orthorhombic lattice with space group P2 1 2 1 2 1 . Its unit cell parameters: a = 6.7307( 5 μ(Mo-Kα) = 0.517 mm −1 , and D calc = 1.569 g/cm 3 . The final refinement resulted in R1 of 0.0366 [I > 2σ(I)], wR2 of 0.0911 with S = 1.03.…”

“…The Rint and Rsigma were measured as 0.0300 and 0.0268, respectively. The compound crystallized in an orthorhombic lattice with space group P2 1 2 1 2 1 , exhibiting unit cell parameters: a = 9.2768(5) Å, b = 6.6079(4) Å, c = 21.6333(13) Å, V = 1326.12(13) Å 3 ; Z = 4, μ(Mo-Kα) = 0.515 mm −1 , and D calc = 1.563 g/cm 3 . The final refinement yielded R1 of 0.0475 [I > 2σ(I)], wR2 of 0.1439, with S = 1.07.…”

“…At present, chiral pesticides constitute 25% of the global pesticide sales, with common types including herbicides, insecticides, and fungicides. Notable chiral insecticides include bispropylene and synthetic pyrethroids, , while chiral herbicides include clodinafop and imazethapyr. , Furthermore, the asymmetric center in the chiral pesticide structure introduces enantiomers possessing diverse distributions, fates, biomagnification potentials, and cytotoxicities . These stereoisomers exhibit varying toxicities, biological activities, and target organisms.…”

Enantioselective Degradation and Bioactivity Mechanism of a New Chiral Fungicide Fluindapyr in Paddy Ecosystems

“…On the other hand, fluindapyr contains a single chiral center atom, allowing for a pair of enantiomers (Figure S1). In some organisms and environmental media, the environmental behavior, biological activity, and toxicity of chiral pesticide enantiomers may exhibit significant differences even though each enantiomer has the same physical and chemical properties. − Therefore, the traditional risk evaluation for chiral pesticides based on a racemate mixture may not produce accurate results. Many studies have reported a stereoselective phenomenon of chiral fungicides in environmental media and organisms.…”