Enantioselective Distribution, Degradation, and Metabolite Formation of Myclobutanil and Transcriptional Responses of Metabolic-Related Genes in Rats

Abstract

Myclobutanil (MT), a chiral fungicide, can be metabolized enantioselectively in organisms. In this work, the associated absorption, distribution, metabolism and transcriptional responses of MT in rats were determined following a single-dose (10 mg·kg body weight) exposure to rac-, (+)- or (-)-MT. The enantiomer fractions (EFs) were less than 0.5 with time in the liver, kidney, heart, lung, and testis, suggesting preferential enrichment of (-)-MT in these tissues. Furthermore, there was conversion of (+)-form to (-)-form in the liver and kidney after 6 h exposure to enantiopure (+)-MT. Enrichment and degradation of the two enantiomers differed between rac-MT and MT-enantiomers groups, suggesting that MT bioaccumulation is enantiomer-specific. Interestingly, the degradation half-life of MT in the liver with rac-MT treatment was shorter than that with both MT-enantiomer treatments. One reason may be that the gene expression levels of cytochrome P450 1a2 ( cyp1a2) and cyp3a2 genes in livers treated with rac-MT were the highest among the three exposure groups. In addition, a positive correlation between the expression of cyp2e1 and cyp3a2 genes and rac-MT concentration was found in livers exposed to rac-MT. Simultaneously, five chiral metabolites were detected, and the enantiomers of three metabolites, RH-9090, RH-9089, and M2, were separated. The detected enantiomers of (+)-MT metabolites were in complete contrast with those of (-)-MT metabolites. According to the results, a metabolic pathway of MT in male rats was proposed, which included the following five metabolites: RH-9089, RH-9090, RH-9090 Sulfate, M1, and M2. The possible metabolic enzymes were marked in the pathway. The findings of this study provide more specific insights into the enantioselective metabolic mechanism of chiral triazole fungicides.

Looking beyond the Active Substance: Comprehensive Dissipation Study of Myclobutanil-Based Plant Protection Products in Tomatoes and Grapes Using Chromatographic Techniques Coupled to High-Resolution Mass Spectrometry

“…In Figure S7.2, the correlation between C9–H3 and C9–H7 can be seen as a small signal. This confirms the presence of a ketone group, which appeared as a small signal in the 13 C NMR experiment …”

“…Besides, after 70–80 days, their concentration increased, corresponding to the lowest myclobutanil concentration. Particularly, RH-9089 appeared after 20 days since it was formed from RH-9090 (which begins to appear at 2 h) . While 7-myclobutanil was only detected in tomatoes at 5 days, 1-myclobutanil was only identified in grapes from 1 day to 40 days after application.…”

“…Although myclobutanil and its dissipation have been extensively studied, even at different temperatures, only a few metabolites have been elucidated and they could be as toxic as parent compounds, and this is an important issue. In bibliography, several metabolites, such as RH-9090, RH-9089 (produced by plant metabolism), RH-0294 (stable in milk), RH-8812, RH-8813, and butyric acid (soil metabolite), in addition to common triazole metabolites such as free triazole, 1,2,4-triazole (T), and its two conjugates, triazolylalanine (TA) and triazolylacetic acid (TAA), (Table ) were described. − It has to be clarified that the metabolites/impurities RH-8812 and RH-8813 are mentioned in the European Food Safety Authority (EFSA) document, but information about them was not found, including their formula or structure, so they cannot be included in conventional databases. The study of both known and unknown metabolites is an important issue since, for example, for known metabolites, there are no toxicity data, and the EFSA suggested that they have the same range of toxicity as the parent compound …”

Prediction and Characterization of CYP3A4-mediated Metabolisms of Azole Fungicides: an Application of the Fused-grid Template* system

“…Myclobutanil is used as racemate and oxidized in a stereoselective manner in the body 32,33) . This fungicide is metabolized extensively in rats and thus the parent chemicals represent a few percent of the total excretion 32) .…”

Enantioselective toxic effects of mefentrifluconazole in the early life stage of zebrafish (Danio rerio)

“…Prothioconazole induced developmental toxicity, lipid peroxidation, oxidative damage, and cardiovascular effects on zebrafish embryo 4,5 . In addition, 75% of triazole fungicides are chiral 6 . In general, enantiomers of chiral pesticide exhibit enantioselective behaviors in the aspects of bioactivity, toxicity and degradation 7 .…”