Enantioselective Toxicity And Degradation Of Some Endocrine Disrupters

A great number of man-made chemicals are chiral.And the significance of enantioselectivity in their fate and effects in the environment has just started to receive attention.However the further study of the enantioselective toxicity of chiral chemicals were delayed because of lacking of enantiomeric pure samples and suitable evaluating models.In this study,we try to challenge above difficult study.Firstly,we selected enantiomeric pure acetofenate(AF)andλ-cyhalothrin(LCT)as targeted insecticides,which would be enantioseleetive separated on selected chiral columns by high performance liquid chromatography(HPLC).Secondly,we studied their enantioselective in development toxicitiy,endocrine disruption and immunotoxicity.Thirdly,the abiotic oxidation of 17β-estradiol(E₂)in soil was further studied,and the synthetic MnO₂ was used to study the oxidative removal of aqueous steroid estrogens.Finally,The availability of clomazone to barnyardgrass in the soil in the absence and presence of burned rice straw was tested.With different chiral columns,HPLC was used for enantioselective separation the two insecticides.The AF and LCT enantiomers were baseline separated on all the comlumn (Chiralpak AD,Chiralpak AS,Chiralcel OD,Chiralcel OJ and Sumichiral OA-2500I)tested under optimized conditions.In most eases,better separations were achieved at lower temperatures(e.g.,20℃)and lower levels of polar modifiers(≤5%)in mobile phase.Pure enantiomers were obtained on Chiralcel OD.Optical rotatory dispersion(ORD)and circular dichroism(CD)detectors were used to determine the elution order and CD spectra of the enantiomers.The absolute configuration of AF enantiomers was identified as S-(+)-AF and R-(-)-AF by the octant rule from force-field calculations and CD spectra.Models of both in vivo and in vitro were used for evaluationg the enantioselective in development toxicitiy,endocrine disruption and immunotoxicity.The individual enantiomers of AF and LCT were used in 4-day zebrafish embryo-larval bioassays,and a series of developmental endpoints were measured,and compared.Quantitative real-time polymerase chain reaction(qRT-PCR)was used to investigate the expressions of estrogen receptor alpha (ERα)in zebrafish embryo exposed to varying enantiomers of AF.Significant enantioselectivity of AF and LCT were observed in developmental toxicities such as yolk sac edema,crooked body and pericardial edema.And the data of qRT-PCR showed that there was about 3.2-fold in induction the mRNA levels of ERαbetween fish exposed to(+)-AF and (-)-AF.While the enantiomers of AF showed no difference in acute toxicity,the (-)-enantiomer of LCT was＞162 times more toxic than its antipode to zebrafish in the acute test.This may be caused by the difference in the properties of the two chemicals.Significant enantioselectivity of LCT were found in endocrine disruption with human breast carcinoma cell line MCF-7 and immune toxicity with human macrophage cell line RAW264.7.The(-)-enantiomer was stronger than the(+)-enantiomer in MCF-7 cell proliferation and induction of pS2 and ERαmRNA expression.Similar enantioselectivity was observed in RAW264.7 cell growth,apoptosis and alteration of p53 mRNA level.Soil and water contamination by estrogens has raised worldwide concern over their potential human health and ecological effects.A thorough understanding of their environmental fate is imperative for proper risk assessment and development of effective remediation technologies.By selectively removing manganese oxides while preserving other soil components,the degradation of 17β-estradiol(E₂)in sterile soil and Mn-free soil,along with the concentration of Mn(â…¡),was determined.In 0.075 g ml^-1soil slurry,E₂ with and initial concentration of 0.0267μmol g^-1was rapidly degraded and near equimolar estrone(E₁) accumulated over 4-d reaction time.No other products were detected in soil.A mass balance involving E₂ and E₁ existed throuthout the reaction time.The E₂ degradation was thus and oxidation process and E₁ was the product,in which the hydroxyl at position 17 of E₂ was oxidized to a carbonyl.The concurrent relaeas of Mn(â…¡)during E₂ oxidation and a lack of E₂ oxidation in Mn-free soil together demonstrated that manganese oxides were the sole component responsible for E₂ oxidation in soil.The degree of E₂ oxidation was higher at higher soil pH than at lower pH,consistent with the fact that the reaction released protons. Sorption of E₂ and E₁ was determined using Mn-free soil.Such data may be more accurate because of the elimination of E₂ oxidation.Using 4×10-5 M synthetic MnO2 at pH4,E₁,E₂ estriol(E₃)and 17α-ethinylestradiol (EE₂),all at 4×10-6 M,were rapidly removed within 220 min,indicating the effectiveness of MnO₂ as oxidizing agent towards estrogens.E₂ removal increased with decreasing pH over the tested range of 4-8,due most likely to increased oxidizing power of MnO₂ and a cleaner reactive surface in acidic solutions.Coexisting metal ions of 0.01(Cu(â…¡),Zn(â…¡),Fe(â…¢)and Mn(â…¡))and Mn(â…¡)released from MnO₂ reduction competed with E₂ for reactive sites leading to reduced E₂ removal.Observed differential suppression on E₂ removal may be related to different speciations of metals,as suggested by the MINTEQ calculations,and hence their different adsorptivities on MnO₂.By suppressing the metal effect,humic acid substantially enhanced E₂ removal.This was attributed to complexation of humic acid with metal ions. With 0.01 M ZnCl₂ in solutions containing 1 mg L^-1humic acid,the binding of humic acid for Zn(â…¡)was determined at 251 mmol g^-1.An in vitro assay using MCF-7 cells indicated a near elimination of estrogenic activities without secondary risk of estrogen solutions treated with MnO2.The adsorption of clomazone by a soil amended with a burned rice straw(BRS)was measured.The availability of clomazone to bamyardgrass in the soil in the absence and presence of BRS was tested.The BRS was 1,000-20,000 times more effective than soil in sorbing clomazone.The sorption of clomazone by soil increased with increasing BRS content in the soil.In a bioassay,the injury of bamyardgrass 9 days after planting decreased with increasing BRS content in soil indicating the effect of BRS on clomazone availability.