Enantioselective Metabolic Mechanism and Metabolism Pathway of Pydiflumetofen in Rat Liver Microsomes: In Vitro and In Silico Study

Computational simulations uncover enantioselective metabolism of chiral triazole fungicides by human CYP450 enzymes: A case study of tebuconazole

Tebuconazole (TEB), a prominent chiral triazole fungicide, has been extensively utilized for plant pathogen control globally. Despite experimental evidence of TEB metabolism in mammals, the enantioselectivity in the biotransformation of R- and S-TEB enantiomers by specific CYP450s remains elusive. In this work, integrated in silico simulations were employed to unveil the binding interactions and enantioselective metabolic fate of TEB enantiomers within human CYP1A2, 2B6, 2E1, and 3A4. Molecular dynamics (MD) simulations clearly delineated the binding specificity of R- and S-TEB to the four CYP450s, crucially determining their differences in metabolic activity and enantioselectivity. The primary driving force for robust ligand binding was identified as van der Waals interactions with CYP450s, particularly involving the hydrophobic residues. Mechanistic insights derived from quantum mechanics/molecular mechanics (QM/MM) calculations established C2-methyl hydroxylation as the predominant route of R-/S-TEB metabolism, while C6-hydroxylation and triazol epoxidation were deemed kinetically infeasible pathways. Specifically, the resulting hydroxy-R-TEB metabolite primarily originates from R-TEB biotransformation by 1A2, 2E1 and 3A4, whereas hydroxy-S-TEB is preferentially produced by 2B6. These findings significantly contribute to our comprehension of the binding specificity and enantioselective metabolic fate of chiral TEB by CYP450s, potentially informing further research on human health risk assessment associated with TEB exposure.

Systematic health risks assessment of chiral fungicide famoxadone: Stereoselectivities in ferroptosis-mediated cytotoxicity and metabolic behavior

Famoxadone is a chiral fungicide frequently found in the environment and agricultural products. However, the health risks of famoxadone enantiomers are not well understood. This study investigated the stereoselective cytotoxicity and metabolic behavior of famoxadone enantiomers in mammals. Results showed that R-famoxadone was 1.5 times more toxic to HepG2 cells than S-famoxadone. R-famoxadone induced more pronounced ferroptosis compared to S-famoxadone. It caused greater upregulation of genes related to iron transport and lipid peroxidation, and greater downregulation of genes related to peroxide clearance. Furthermore, R-famoxadone induced more severe lipid peroxidation and reactive oxygen species (ROS) accumulation through ACSL4 activation and GPX4 inhibition. Additionally, the bioavailability of R-famoxadone in mice was six times higher than that of S-famoxadone. Liver microsome assays, cytochrome P450 (CYP450) inhibition assays, human recombinant CYP450 assays, and molecular docking suggested that the lower binding affinities of CYP2C8, CYP2C19, and CYP2E1 for R-famoxadone caused its preferential accumulation. Overall, R-famoxadone poses a higher risk than S-famoxadone due to its greater cytotoxicity and persistence. This study provides the first evidence of ferroptosis-induced stereoselective toxicity, offering insights for the comprehensive health risk assessment of chiral famoxadone and valuable references for the application of high-efficiency, low-risk pesticide enantiomers.

Comparative pharmacokinetic investigation on crocetin in hyperlipidemia and normal rats after oral administration

Crocetin as one of the main components of saffron possesses a lot of pharmacological effects, especially the beneficial effects in the treatment of hyperlipidemia. However, the pharmacokinetics of crocetin in the pathological state of hyperlipidemia has not been reported. In present study, the pharmacokinetics of crocetin in hyperlipidemia rats after oral administration of crocetin was investigated and the possible mechanisms for the pharmacokinetics were explored. High-fat diet was used to induce hyperlipidemia in rats. The pharmacokinetics of crocetin was investigated in hyperlipidemia and normal rats after oral and intravenous administration of crocetin, and the possible mechanisms of the pharmacokinetic changes were investigated in terms of metabolism and absorption using in vitro incubation with liver microsomes and the everted gut sac method, respectively. Results indicated that the AUCs of crocetin in hyperlipidemia rats after oral administration of crocetin were remarkably decreased when compared with those in normal rats. Moreover, crocetin was also metabolized more rapidly in the liver microsomes of hyperlipidemia rats and intestinal absorption of crocetin was significantly reduced in hyperlipidemia rats. It suggested that the remarkably decreased AUCs of crocetin in hyperlipidemia rats might partly result from the result of faster metabolic elimination and reduced absorption of crocetin in the hyperlipidemia pathological state. And the present investigations conducted on rats demonstrate that further investigations into the kinetics of crocetin in humans with hyperlipidemia are necessary in order to ensure an adequate dosage in this indication.

Enantioselective metabolism of novel chiral insecticide Paichongding by human cytochrome P450 3A4: A computational insight

As a novel chiral neonicotinoid insecticide, Paichongding (IPP) has been widely applied in agriculture due to its excellent insecticidal activity. However, the enantioselective metabolism of IPP stereoisomers (5R7R-IPP, 5S7S-IPP, 5R7S-IPP, and 5S7R-IPP) mediated by enzymes in non-target organisms, especially the cytochrome P450s (CYPs), remains unknown. To address this knowledge gap, we developed an integrated computational framework to elucidate the binding interactions and enantioselective metabolism of IPP stereoisomers in human CYP3A4. The results reveal that 5R7R-IPP shows much stronger binding affinity to CYP3A4 than 5S7S-IPP, while enantiomers 5R7S-IPP and 5S7R-IPP have no essential difference in their binding potential, owing to their specific interactions with key CYP3A4 residues. Although enantiomers 5R7R-IPP and 5S7S-IPP feature distinct binding modes resulting from the chiral differences, their transformation activities are slightly different, with C5 and C13 being the primary metabolic sites, respectively. In contrast, CYP3A4 preferably metabolizes 5R7S-IPP over 5S7R-IPP. The metabolism of epimers 5R7R-IPP and 5R7S-IPP share C5-hydroxylation routes due to the conserved 5R-conformaitons, but differ with the transformation routes at C11/C13 and C3 sites. The 7R-chirality of 5S7R-IPP significantly reduces the metabolic potency compared to 5S7S-IPP. CYP3A4-catalyzed hydroxylation and desaturation of IPP stereoisomers generate various chiral metabolites, with C5- and C13-hydroxyIPPs further transforming into depropylated products. Furthermore, the toxicity assessment reveals that IPP, along with the majority of its hydroxylated, desaturated, and depropylated metabolites, can potentially induce adverse effects on human health, specifically hepatotoxicity, respiratory toxicity, and carcinogenicity. This study provides valuable insights into the enantioselective fate of chiral IPP metabolism by CYP3A4, and the identified metabolites can serve as potential biomarkers for monitoring IPP exposure and associated health risk in human body.

Enantioselective uptake, translocation, and biotransformation of pydiflumetofen in wheat (Triticum aestivum L.): Insights from chiral profiling and molecular simulation

Pydiflumetofen (PYD), a highly effective and broad-spectrum fungicide, is commonly employed for the control of fungal diseases. In this study, the uptake, translocation, and biotransformation of PYD by wheat (Triticum aestivum L.) were firstly investigated at a chiral level. The findings revealed that the residue concentration of R-PYD in wheat was higher than that of S-PYD, because of its higher uptake rate (k1 = 0.0421 h-1) and lower elimination rate (k2 = 0.0459 h-1). Additionally, R-PYD exhibited higher root bioconcentration factors and translocation factors compared with S-enantiomer, indicating R-PYD was more easily accumulating in roots and translocating to shoots. Furthermore, a total of 9 metabolites, including hydroxylated, demethylated, demethoxylated, dechlorinated, hydrolyzed, and glycosylated-conjugated products, were detected qualitatively in wheat roots or shoots. Symplastic pathway-mediated uptake, which predominantly relied on aquaporins and anion channels, was confirmed by root adsorption and inhibition experiments, without displaying any enantioselective effect. Molecular simulations demonstrated that R-PYD exhibited stronger binding affinity with TaLTP 1.1 with a lower grid score (-6.79 kcal/mol), whereas weaker interaction with the metabolic enzyme (CYP71C6v1) compared to the S-enantiomer. These findings highlight the significance of plant biomacromolecules in the enantioselective bioaccumulation and biotransformation processes. Importantly, a combination of experimental and theoretical evidence provide a comprehensive understanding of the fate of chiral pesticides in plants from an enantioselective perspective.

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

Fluindapyr is a novel chiral succinate dehydrogenase inhibitor used to control fungal diseases. The enantioselective effects of fluindapyr in paddy ecosystems are unknown. We developed a new chiral determination method of fluindapyr using ultrahigh performance liquid chromatography tandem mass spectrometry. The absolute configuration of the fluindapyr enantiomers was identified by an electron circular dichroism model. A new husk-based biochar material was used to optimize and establish a QuEchERs method for paddy soil determination. Under anaerobic conditions, the half-lives of R-fluindapyr and S-fluindapyr in paddy soil were 69.6 and 101.8 days, respectively. R-fluindapyr degraded more rapidly than S-fluindapyr. S-fluindapyr was 87.8 times more active against Rhizoctonia solani than R-fluindapyr. The enantioselective bioactivity mechanism was illustrated by molecular docking between the fluindapyr enantiomers and SDH of R. solani. The binding powers of R-fluindapyr and S-fluindapyr to proteins were -32.12 and - 42.91 kcal/mol, respectively. This study reports the stereoselectivity of fluindapyr about determination, degradation, bioactivity, and its mechanism. It provides a foundation for an in-depth study of fluindapyr at the enantiomer level.

Comprehensive study of pydiflumetofen in Danio rerio: Enantioselective insight into the toxic mechanism and fate

Pydiflumetofen (PYD) is primarily used to control fungal disease. The potential risks posed by PYD enantiomers to the aquatic ecosystem are currently unclear. In this study, the enantioselective toxicity and fate of PYD in Danio rerio were investigated, and the enantioselective toxic mechanism and metabolic pathway were explored. The acute toxicity of R-PYD was 10.7-14.7-fold than that of S-PYD against Danio rerio embryos, larvae, and adults. Meanwhile, R-PYD presented a stronger effect on embryo hatching and abnormalities, adult tissue damage and oxidative stress. R-PYD inhibited the succinate dehydrogenase (SDH) activity more than S-PYD because of its better interaction with SDH with a lower binding free energy (-59.35 kcal/mol), explaining the mechanism of enantioselective toxicity. Remarkable enantioselectivity was observed in uptake, distribution, and elimination. R-PYD showed preferential uptake with the higher uptake rate constants and slow metabolism with a longer half-life, resulting in the bioaccumulation of R-PYD with higher BCF_k (7.37 at 0.05 mg/L and 14.69 at 0.2 mg/L). Besides, muscle is an important tissue for PYD accumulation, existing potential food risk. Eleven PYD metabolites were qualitatively identified, and the metabolic pathway was proposed, including hydroxylation, N-demethylation, demethoxylation, hydrolysation (phase Ⅰ), and acetylation and glucuronidation (phase Ⅱ). The predicted toxicity of the metabolite indicated that several highly toxic metabolites need to be considered in the future. This study provides a new perspective for evaluating the ecological and human health risks of chiral pesticides.