Study On The Toxicokinetics And Sonocatalytic Degradation Mechanism Of Chiral Pesticide Napropamide

The chiral pesticide napropamide is an amide pre-emergence herbicide with a wide spectrum of weed control,which has an efficient killing effect on various annual gramineous weeds and some dicotyledonous weeds.In this paper,rat and mouse were used as test organisms,napropamide was used as the research object,and ultra high performance liquid chromatography-triple quadropole mass spectrometry（UHPLC-QQQ/MS）was used to detect napropamide.The toxicokinetic differences of napropamide in mammals were studied at the enantiomeric level,and the simulated metabolites in vitro were studied by high performance liquid chromatography–quadropole-time of flight mass spectrometry（HPLC-Q-TOF/MS）.In addition,the degradation ability and degradation mechanism of napropamide by sonocatalytic technology combined with sonocatalyst were studied,and the degradation effect was also evaluated by UHPLC-QQQ/MS.The main research contents are as follows:1.In this paper,an analysis method of reversed-phase UHPLC-QQQ/MS combined with chiral CHIRALPAK^?IG chiral column was established and optimized for the separation and determination of napropamide enantiomers in various biological samples（including plasma,tissues,feces and urine）:acetonitrile and 5m M ammonium acetate aqueous solution were used at a ratio of 80:20（v/v）,and the flow rate was 0.6 m L/min.Further methodological investigation proved that this method has good specificity,linearity,precision,accuracy,stability,low limit of quantitation,and which extraction recovery,matrix effect and other indicators are in line with the requirements for the detection of napropamide enantiomers in biological samples to provide theoretical and practical basis.On this basis,the enantiomer monomer was prepared and the absolute configuration was identified（peak1 was S-napropamide,peak2 was R-napropamide）.2.Plasma pharmacokinetic studies by gavage and tail vein injection showed that the bioavailability of napropamide enantiomers was low,only 0.85%and 0.80%.Under the premise of gastric emptying,the absorption and utilization of napropamide in the intragastric administration group was faster(t_max1=0.23 h,t_max2=0.27 h),but decreased to a lower level within 4 h,indicating that there may be a rapid metabolic process in the body.Because of this,the content of napropamide in plasma was low（AUC₁=9.41μg·h/L,AUC₂=19.45μg·h/L）,but the difference was obvious.The AUC of R-napropamide was about twice that of S-napropamide.In addition,the apparent distribution volume difference between the intragastric group and the tail vein injection group was large,indicating that the napropamide absorbed through the digestive tract requires a large amount of tissue and body fluid to dilute,which may be widely distributed and resident in the tissues and organs of the body,and there is a potential threat to the body.3.Further study on the distribution of its tissues showed that the enantiomers of napropamide were detected in 15 tissues,and stomach>>small intestine>>pancreas≈liver>>spleen>large intestine>fat>cecum>kidney>bladder>>heart>muscle>testis>lung>brain,which further proved the rationality of large apparent distribution volume.Among them,except for heart,muscle and fat,most tissues showed that the content of R-napropamide was significantly higher than that of S-napropamide.Secondly,napropamide was easily adsorbed on the inner wall of the gastrointestinal tract during intragastric administration.Because of its high fat solubility,it was more easily absorbed by the inner wall of the gastrointestinal tract,so the gastrointestinal tissue showed the maximum concentration(C_max1=74.6μg/g,C_max2=100.3μg/g).In addition,due to a small amount of detection in brain tissue,it shows that napropamide has the possibility of breaking through the blood-brain barrier,suggesting that there may be potential harm to the brain.4.The metabolites of napropamide co-incubated with liver microsomes and serum were identified by HPLC-Q-TOF/MS.There were 7 metabolites of napropamide in liver microsomes and only 1 metabolite in serum.Due to the presence of a large number of CYP450 enzymes in liver microsomes,phase I metabolic processes such as dealkylation,hydroxylation,and dehydrogenation can occur,while the metabolic pathway in serum is relatively simple,and the metabolic processes of thiolation and dealkylation can occur.In addition,the binding of CYP2E1 to napropamide enantiomers was simulated by computer molecular docking.The protein and napropamide enantiomers were combined with hydrogen bonds through amino acid residue Thr 303,and due to the existence of hydrophobic interaction,the binding ability of hydrogen bonds was different,and the binding ability of S enantiomer was stronger.This also confirms that the phenomenon that the content of S-napropamide in plasma and most tissues is lower than that of R-napropamide may be affected by the difference in the metabolic level of enantiomers in vivo,and the S-enantiomer metabolic ability is stronger.5.The urine pretreatment method was optimized,and the three-time ethyl acetate extraction method had higher detection sensitivity than the acetonitrile precipitation method,and the matrix interference was smaller.By studying the content changes and cumulative excretion of enantiomers in the excreta of rats for120 h after intragastric administration of napropamide,it was found that the prototype excretion rate of napropamide was low（the cumulative excretion rate was less than0.4‰）,and it was mainly excreted through feces.The content in urine was lower（the cumulative excretion was as low as 0.01‰）,but there was a small amount of continuous detection in urine for 120 h,which was consistent with previous studies.6.Due to the stable nature and long half-life of napropamide,it is easy to produce residues in soil,plants and water,so advanced oxidation process（AOPs）are tried to remove it from water.Spherical calcium tungstate（Ca WO₄）was prepared by hydrothermal method,and its morphology was adjusted by controlling the p H of the Ca WO₄precursor.XRD,SEM,DRS and electrochemical properties were characterized to determine the morphology,crystal phase and band gap energy of the prepared Ca WO₄.The sonocatalytic degradation of napropamide simulated wastewater was carried out by ultrasonic combined with sonocatalyst and initiator.The effects of Ca WO₄precursor p H,Ca WO₄addition,ultrasonic power,ultrasonic temperature and ultrasonic time on the activity of sonocatalytic degradation of napropamide were investigated.The results showed that the degradation effect of napropamide by ultrasound alone was limited,while the degradation effect could be significantly improved by using Ca WO₄acoustic catalyst with precursor p H=7,adding 2 g/L,adding 0.5 m M K₂S₂O₈,combined with 300 W ultrasonic power and40°C ultrasonic temperature.The degradation rate reached 95.7%in 20 min and 100%in 30 min.Through reactive oxygen species（ROS）capture experiments,it was investigated that the types of ROS that played a major role in the degradation of napropamide were h⁺,·OH,·SO₄^2-,and the intensity of action was gradually weakened,and·O₂^-had little effect.On this basis,the possible degradation mechanism was speculated.In summary,the results of toxicokinetics showed that there were significant differences in napropamide enantiomers in plasma,most tissues and feces,but there was no significant difference in heart,muscle,fat and urine.The existence of enantiomeric differences was affected by the difference in metabolic capacity in vivo.The results of sonocatalytic research show that the combination of sonocatalyst and initiator by sonocatalytic technology can efficiently remove napropamide in sewage.The results of this study provide some theoretical support for the future development of napropamide monomer,and also provide new ideas for agricultural wastewater treatment.