Design, Synthesis And Antibacterial Activity Of Novel 1,3,4-thiadiazole Derivatives Containing Amide Structure And Their Mechanism Of Actio

In this paper,using the principle of active splicing,the amide structure was introduced into the skeleton of 1,3,4-thiadiazole.A series of 1,3,4-thiadiazole derivatives containing an amide were designed and synthesized.Two rice pathogenic bacteria,Xanthomonas oryzae pv.oryzae（Xoo）and Xanthomonas oryzae pv.oryzicola（Xoc）of rice were used as research objects to test the antibacterial activities in vitro of compounds 1-30 against the two pathogens.Based on the EC₅₀ values of compounds 1-29 against Xoo and Xoc,two Co MFA models were established,and the structure of the compounds were optimized according to the model,and a compound30 with higher antibacterial activity was obtained.The bacterial activities in vivo of compound 30 against rice bacterial leaf blight and rice bacterial leaf break were tested by leaf-cutting method and pressure osmosis method.The effect of compound 30 on the surface morphology of the two pathogenic bacterias were observed by scanning electron microscope.Compound 30 with better protective activity against rice bacterial leaf break,the mechanism of action of compound 30 was analyzed through defensive enzyme activity and label-free quantitative proteomics.The main research work is as follows:1.The 1,3,4-thiadiazole structural framework was used as the leader,through active splicing principle,introducing amide structure with a wide range of biological activities,designed and synthesized a series of 1,3,4-thiadiazole derivatives containing an amide.The synthesized series of target compounds were characterized by ¹H NMR,¹³C NMR and HRMS to determine the structure of the target compounds.2.The turbidimetric method was used to test the antibacterial activities in vitro of1,3,4-thiadiazole derivatives containing an amide against Xoo and Xoc.The thiodiazole copper was used as control agent.The results shown that compounds 2,5,6,7,17,24,25 and 28 showed significant antibacterial activitiess against Xoo,with EC₅₀ values of 21.0,31.8,51.8,38.1,37.7,25.8,46.3 and 43.5 mg/L,respectively,which were better than the control agent thiodiazole copper（92.5 mg/L）.Meanwhile,compounds 2,5,7,17,24,25 and 28 also showed antibacterial activities against Xoc,with EC₅₀ values of 17.1,39.3,41.6,49.2,31.5,49.1 and 46.9 mg/L,respectively,which were better than the control agent thiodiazole copper（99.6 mg/L）.3.Two Co MFA models were established based on the EC₅₀ values of compounds1-29 against Xoo and Xoc,the structure of the compounds was optimized and modified according to the Co MFA model,and a compound 30 with higher antibacterial activity was designed and synthesized.The EC₅₀ values of compound 30against Xoc and Xoo were 2.1 and 1.8 mg/L,respectively,and the experimental and predicted residual values of compound 30 were 0.2359 and 0.1769,respectively,and the predicted results are in good agreement with the actual values,which indicates that the model has a good predictive effect.4.Thiodiazole copper was used as a control agent,the leaf-cutting method and the pressure osmosis method were used to test the antibacterial activities in vivo of compound 30 against rice bacterial leaf blight and rice bacterial leaf break.The results shown that the protective and curative activities of compound 30 at concentration of200 mg/L against rice bacterial leaf blight were 51.3%and 46.1%,respectively,which were superior to thiodiazole copper（37.8%and 38.5%）.The protective and curative activities of compound 30 at concentration of 200 mg/L against rice bacterial leaf streak were 45.9%and 40.5%,respectively,which were better than thiodiazole copper（36.2%and 31.1%）.5.The scanning electron microscope was used to observed treatment with compound 30 the effect of surface morphology of the two pathogenic bacterias.Compound 30 can destroy the surface morphology of Xoo and Xoc,affect the normal growth of cells,and weaken their pathogenic ability.6.Through the rice defense enzyme activities test and quantitative proteomic analysis,the results shown that compound 30 can increase the relevant defense enzyme activities（SOD,POD and CAT）and up-regulate specific proteins related to the glycolysis/gluconeogenesis pathway to protect The normal growth and development of rice,and improve disease resistance.