| Dufulin,a novel plant antiviral agents created by China,has been widely used on tobacco,cucumber and rice to prevent and control viral disease.Since the synthesis process is relatively simple,the cost is low,Dufulin has a good application prospect.In recent years,studies on the environmental behavior of Dufulin in crop-soil and water-sediment system have been carried out gradually.However,there have been no reports on the distribution and metabolism of Dufulin in livestock and poultry.It is of great practical significance to clarify the distribution and metabolism of Dufulin in poultry for further understanding of its safety and dietary risks.In this paper,white laying hens（Gallus gallus domesticus）was selected,with[thiazyl-2-14C]-Dufulin and[benzyl-14C]-Dufulin as isotope tracers,to clarify the excretion and residual distribution in tissues,comprehensively using 14C tracing technology and modern instrument analysis technology.On this basis,the metabolism in laying hens was studied and 4 kinds of metabolites were identified.The possible metabolic pathways were also inferred.This study was aiming to complement the distribution and metabolism data of Dufulin in poultry,and provide theoretical basis and data support for scientific safety evaluation of Dufulin in poultry.The main results are as follows:（1）[thiazyl-2-14C]-Dufulin and[benzyl-14C]-Dufulin were given orally to white laying hens(1.1 mg·kg-1·d-1)lasting for 7 days.The total recovery of Dufulin was 90.10%and 91.48%,respectively,which met the requirements of radioactive material balance.（2）Dufulin was mainly discharged through excretion.The accumulative excretion recovery of the two labeled test substances within 7 days were 82.24%and 84.32%,respectively.The radioactivity of the two labeled test substances in excretion within 12hours after the first day administration was 63.42%and 63.48%.There was no significant difference in the excretion of the two 14C-Dufulin.（3）The results showed that the total residues of two kinds of labeled test substances in tissues were 3.81%and 3.85%of applied amount,among which the residues in stomach was relatively the highest,2.14%and 2.11%.While the radioactive residues in lung,kidney,fat and pancreas were not more than 0.01%of applied amount,no residual radioactivity was detected in in brain,heart,spleen,ovary,egg and muscles.After the assessment of dietary exposure,the residues of toxic fluorine phosphorus in the tissues of laying hens would not cause dietary risk.（4）The analysis method based on radioisotope tracing combined with high performance liquid chromatography and high resolution mass spectrometry was established.Four kinds of metabolites in excretion,DFL-M1,DFL-M2,DFL-M3 and DFL-M4,were identified.DFL-M4,[（2-Fluoro-phenyl）-（6-hydroxy-4-methyl-benzothiazol-2-ylamino）-methyl]-phosphonic acid diethyl ester,was hydroxylation metabolite of Dufulin.DFL-M3,[（2-Fluoro-phenyl）-（4-methyl-benzothiazol-2-ylamino）-methyl]-phosphonic acid monoethyl ester,was O-dealkylation of Dufulin.DFL-M1,[（2-Fluoro-phenyl）-（6-hydroxy-4-methyl-benzothiazol-2-ylamino）-methyl]-phosphonic acid monoethyl ester,was hydroxylation and O-dealkylation of Dufulin.DFL-M2,6-（2-{[（Diethoxy-phosphoryl）-（2-fluoro-phenyl）-methyl]-amino}-4-methyl-benzothiazol-6-yloxy）-3,4,5-trihydroxy-tetrahydro-pyran-2-carboxylic acid,was the metabolite formed by hydroxylation-DFL conjugated with glucuronic acid.DFL-M4and DFL-M2 were the main metabolites.This study also confirmed that Dufulin in laying hens would be metabolized and excreted in the form of DFL,DFL-M4 and DFL-M2.（5）The possible metabolic pathways of Dufulin in laying hens could be divided into two processes:phase I metabolism and phase II metabolism.Phase I metabolism was mainly hydroxylation and O-dealkylation reactions to form DFL-M4,DFL-M3 and DFL-M1.Phase II metabolism mainly included that under the action of UDP-glucuronosyltransferases（UGTs）,DFL-M4 conjugated with glucuronic acid in laying hens. |
