Alpha-cypermethrin (α-CP), [(RS)-a-cyano-3-phenoxy benzyl (1RS)-cis-3-(2, 2-dichlorovinyl)-2, 2-dimethylcyclopropanecarboxylate], comprises a diastereoisomer pair of cypermethrin, which are (+)-(1R-cis-αS)–CP (insecticidal) and (−)-(1S-cis-αR)–CP (inactive). In this experiment, the stereoselective degradation of α-CP was investigated in rat liver microsomes by high-performance liquid chromatography (HPLC) with a cellulose-tris- (3, 5-dimethylphenylcarbamate)-based chiral stationary phase. The results revealed that the degradation of (−)-(1S-cis-αR)-CP was much faster than (+)-(1R-cis-αS)-CP both in enantiomer monomers and rac-α-CP. As for the enzyme kinetic parameters, there were some variances between rac-α-CP and the enantiomer monomers. In rac-α-CP, the V_max and CL_int of (+)-(1R-cis-αS)–CP (5105.22 ± 326.26 nM/min/mg protein and 189.64 mL/min/mg protein) were about one-half of those of (−)-(1S-cis-αR)–CP (9308.57 ± 772.24 nM/min/mg protein and 352.19 mL/min/mg protein), while the K_m of the two α-CP enantiomers were similar. However, in the enantiomer monomers of α-CP, the V_max and K_m of (+)-(1R-cis-αS) -CP were 2-fold and 5-fold of (−)-(1S-cis-αR)-CP, respectively, which showed a significant difference with rac-α-CP. The CL_int of (+)-(1R-cis-αS)–CP (140.97 mL/min/mg protein) was still about one-half of (−)-(1S-cis-αR)–CP (325.72 mL/min/mg protein) in enantiomer monomers. The interaction of enantiomers of α-CP in rat liver microsomes was researched and the results showed that there were different interactions between the IC₅₀ of (−)- to (+)-(1R-cis-αS)-CP and (+)- to (−)-(1S-cis-αR)-CP(IC_50(−)/(+) / IC_50(+)/(−) = 0.61). Chirality 28:58–64, 2016. © 2015 Wiley Periodicals, Inc.

Enantiomeric separation of six chiral pesticides by high-performance liquid chromatography with permethylated β-cyclodextrin (β-PM) chiral stationary phase were tested under reversed phase conditions. The influences of water composition from 10% to 45% in the mobile phase and column temperatures from 0°C to 40°C on the separation were investigated. Chromatographic parameters including selectivity factors (α), retention factors (k), and resolution factors (Rs) were selected to evaluate the separation efficiency in different conditions. Baseline separation was obtained for diclofop-methyl, fenoxaprop-ethyl, tebuconazole, and triticonazole, and Rs of these pesticides were greater than 1.5. However, etoxazole and lactofen were partially separated in all experiments. The parameters of α and k were decreased by the increasing temperature for all investigated pesticides, but the best resolution for etoxazole (Rs = 0.94) and lactofen (Rs = 0.59) was achieved at 20°C, different from the Rs tendency of other pesticides, which decreased with a temperature increase. Chirality 28:409–414, 2016. © 2016 Wiley Periodicals, Inc.

Myclobutanil, (RS)-2-(4-chlorophenyl)-2-(1H-1, 2, 4-triazol-1-ylmethyl)hexanenitrile is a broad-spectrum systemic triazole fungicide which consists of a pair of enantiomers. The stereoselective degradation of myclobutanil was investigated in rat liver microsomes. The concentrations of myclobutanil enantiomers were determined by high-performance liquid chromatography (HPLC) with a cellulose-tris-(3,5-dimethyl-phenylcarbamate)-based chiral stationary phase (CDMPC-CSP) under reversed phase condition. The t_1/2 of (+)-myclobutanil is 8.49 min, while the t_1/2 of (–)-myclobutanil is 96.27 min. Such consequences clearly indicated that the degradation of myclobutanil in rat liver microsomes was stereoselective and the degradation rate of (+)-myclobutanil was much faster than (–)-myclobutanil. In addition, significant differences between two enantiomers were also observed in enzyme kinetic parameters. The V_max of (+)-myclobutanil was about 4-fold of (–)-myclobutanil and the CL_int of (+)-myclobutanil was three times as much as (–)-myclobutanil after incubation in rat liver microsomes. Corresponding consequences may shed light on the environmental and ecological risk assessment for myclobutanil and may improve human health. Chirality 26:51–55, 2013. © 2013 Wiley Periodicals, Inc.

In this contribution, the enantioselective interactions between diclofop (DC) and human serum albumin (HSA) were explored by steady-state and 3D fluorescence, ultraviolet-visible spectroscopy (UV-vis), and molecular modeling. The binding constants between R-DC and HSA were 0.9213 × 10⁵, 0.9118 × 10⁵, and 0.9009 × 10⁵ L · mol^-1 at 293, 303, 313 K, respectively. Moreover, the binding constants of S-DC for HSA were 1.4766 × 10⁵, 1.2899 × 10⁵, and 1.0882 × 10⁵ L · mol^-1 at 293, 303, and 313 K individually. Such consequences markedly implied the binding between DC enantiomers and HSA were enantioselective with higher affinity for S-DC. Steady-state fluorescence study evidenced the formation of DC-HSA complex and there was a single class of binding site on HSA. The thermodynamic parameters (ΔH, ΔS, ΔG) of the reaction clearly indicated that hydrophobic effects and H-bonds contribute to the formation of DC-HSA complex, which was in excellent agreement with molecular simulations. In addition, both site-competitive replacement and molecular modeling suggested that DC enantiomers were located within the binding pocket of Sudlow's site II. Furthermore, the alterations of HSA secondary structure in the presence of DC enantiomers were verified by UV-vis absorption and 3D fluorescence spectroscopy. This study can provide important insight into the enantioselective interaction of physiological protein HSA with chiral aryloxyphenoxy propionate herbicides and gives support to the use of HSA for chiral pesticides ecotoxicology and environmental risk assessment. Chirality 25:719–725, 2013. © 2013 Wiley Periodicals, Inc.