title: Acute toxicity, bioactivity, and enantioselective behavior with tissue distribution in rabbits of myclobutanil enantiomers.
abstract: The enantioselective bioactivity against pathogens (Cercospora arachidicola, Fulvia fulva, and Phytophthora infestans) and acute toxicity to Daphnia magna of the fungicide myclobutanil enantiomers were studied. The (+)-enantiomer in an antimicrobial activity test was about 1.79-1.96 times more active than the (-)-enantiomer. In the toxicity assay, the calculated 24-h LC50 values of the (-)-form, rac-form and (+)-form were 16.88, 13.17, and 11.91 mg/L, and the 48-h LC50 values were 10.15, 9.24, and 5.48 mg/L, respectively, showing that (+)-myclobutanil was more toxic. Meanwhile, the enantioselective metabolism of myclobutanil enantiomers following a single intravenous (i.v.) administration was investigated in rabbits. Total plasma clearance value (CL) of the (+)-enantiomer was 1.68-fold higher than its antipode. Significant differences in pharmacokinetics parameters between the two enantiomers indicated that the high bioactive (+)-enantiomer was preferentially metabolized and eliminated in plasma. Consistent consequences were found in the tissues (liver, brain, heart, kidney, fat, and muscle), resulting in a relative enrichment of the low-activity (-)-myclobutanil. These systemic assessments of the stereoisomers of myclobutanil cannot be used only to investigate environmental and biological behavior, but also have human health implications because of the long persistence of triazole fungicide and enantiomeric enrichment in mammals and humans.
authors.affiliation: Department of Applied Chemistry, China Agricultural University, Beijing, P.R. China.
authors.forename: Mingjing
authors.initials: M
authors.lastname: Sun
authors.forename: Donghui
authors.initials: D
authors.lastname: Liu
authors.forename: Xinxu
authors.initials: X
authors.lastname: Qiu
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhou
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Shen
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D000818:Animals; D001203:Ascomycota / Q000187:drug effects; D002963:Cladosporium / Q000187:drug effects; D003621:Daphnia / Q000187:drug effects; D005659:Fungicides, Industrial / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000633:toxicity; D008297:Male; D008826:Microbial Sensitivity Tests; D009570:Nitriles / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics* / Q000633:toxicity*; D055750:Phytophthora infestans / Q000187:drug effects; D011817:Rabbits; D015203:Reproducibility of Results; D013237:Stereoisomerism; D014018:Tissue Distribution; D023382:Toxicity Tests, Acute / Q000379:methods; D014230:Triazoles / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics* / Q000633:toxicity*
chemical_list: D005659:Fungicides, Industrial; D009570:Nitriles; D014230:Triazoles; C446685:systhane
keywords: acute toxicity; bioactivity; enantioselective degradation; myclobutanil enantiomer; rabbit