Design, Synthesis And Mechanism Of Novel Pentamerone (chalcone) Anti-plant Virus Drug Molecules

?,?-unsaturated carbonyl compounds are widespread in nature,which attracted more and more attention of pharmaceutical and pesticide scientists because of its low toxicity,easy degradation,environmental friendly and good biological activity.At present,it has become one of hot leading structures for structural derivatization.In recent years,scientists have found that three important ?,?-unsaturated carbonyl compounds,including pentadienone,chalcone and ferulic acid have good antiviral activities against plant virus,however,the inhibitory activities of the compounds are still low.To development of efficient and environment friendly small molecule antiviral drugs,five series of ?,?-unsaturated carbonyl derivatives were designed and synthesized based on pentadienone,chalcone,and ferulic acid by using the method of combinatorial chemistry.Their antiviral activities were evaluated by half leaf blight spot method in vivo.Then,the structure-activity relationships(SAR)were performed with 3D-QSAR through simulation calculation,the excellent active compound was obtained based on 3D-QSAR models.The antiviral mechanism of the best antiviral compound was also explored on the basis of Tobacco mosaic virus coat protein(TMV CP)and tobacco resistance of immune activation.The conclusions are shown as follows:1.Based on the our previous work,using ?,?-unsaturated carbonyl pentadienone,chalcone,and ferulic acid as the leading compound,135 novel pentadienone and chalcone derivatives were designed and synthesized,including 17 chalcone derivatives containing a purine moiety(E1–E17),52 chalcone derivatives containing 1,3,4-oxadiazole(thiadiazole)moiety(C1–C26,D1–D26),31 pentadienone derivatives containing 1,3,4-oxadiazole moiety(A1–A31),and 35 chalcone derivatives containing ferulic acid(F1–F35).Their structures were confirmed by 1H NMR,13 C NMR,IR,HRMS and elemental analysis.2.The antiviral activities of the title compounds were evaluated against TMV and CMV by half leaf blight spot method in vivo,the results showed that most of the title compounds exhibited good antiviral activities against TMV and CMV,of which Compouds C4,C6,C17,C20,C24 and C26 have good inactivation activity against TMV,with the EC50 values of 32.18,22.01,33.88,36.72,20.86,and 24.63 ?g/mL,respectively,better than Ningnanmycin(37.97 ?g/mL).Compouds D1,D21,D25 and D26 showed remarkable protection and inactivation activities,with the EC50 values of 196.61,140.36,189.25,204.69 ?g/mL and 33.66,33.87,30.57,35.43 ?g/mL,respectively,both better than Ningnanmycin.Copmpounds A3,A4,A6,A11,A13,A14,A16,A17 and A31 showed remarkable protection actvities against TMV,with the EC50 values of 238.32,178.65,181.53,194.85,234.03,214.92,135.56,224.92,and 123.53 ?g/mL,respectively,which were better than that of Ningnanmycin(241.38 ?g/mL).Compounds F3,F5,F12,F13,F16,F17,F19,F25,F26,F27,F28,F31 and F32 revealed excellent protection activities against TMV,with the EC50 values of 214.21,171.48,218.36,210.14,193.54,112.27,224.24,185.47,164.91,98.78,183.48,215.68 and 198.80 ?g/mL,respectively,which were better than that of Ningnanmycin.Above all,compounds A16?F3?F17 and F27 showed better curative,protection and inactivation activities against TMV and CMV than those of ningnanmycin,of which,compound F27 exhibited the best curative,protection and inactivation activities against TMV and CMV.3.In order to further research the structure-activity relationship(SAR),models of comparative molecular field analysis(CoMFA)and comparative molecular similarity indices analysis(CoMSIA)were established based on 30 pentadienone derivatives containing 1,3,4-oxadiazole moiety.The results showed that those models revealed good predictive power and good reliability,with the values of cross-validated coefficient(q2)and non-cross-validated(r2)of CoMFA and CoMSIA as 0.751,0.775(> 0.5)and 0.936,0.925(> 0.8),respectively.Another,the results of the 3D-QSAR analysis indicated that 5-Ph of 1,3,4-oxadiazole and small group with electron-withdrawing groups on the aromatic ring of pentadienone were favored anti-TMV.Based on these finds,compound A31 was designed,synthesized,and found better protection activity against TMV than that of compound A16.4.Bioassay results found that compound A27 exhibited excellent curative,protective and inactive activities against TMV,in order to reveal the antiviral mechanism of compound F27,the combining constant of compound F27 to TMV CP was measured by the methods of fluorescence spectroscopy(FT)and microscale thermophoresis(MST),the results showed that compound F27 has strong binding to TMV CP,with the Ka and Kd values of 1×105.384 M-1 and 8.1 ?M,which were better than that of Ningnanmycin.Then,two potential binding sites,ARG46 and Lys53 were found by DOCK,and the mutants TMV CPR46 G and TMV CPK53 G were obtained by site-directed mutagenesis.The binding capacity of compound F27 to TMV CPR46 G and TMV CPK53 G were tested by FT and MST.The results showed that ARG46 and Lys53 are two binding sites with the the Ka and Kd values of 1×102.331 M-1,288.5 ?M and 1×103.265,177.5?M.Then,the mechanism of systemic acquired resistance of the compound F27 was performed,including the effects of tobacco on chlorophyll content,photosynthetic rat,defense enzymes activity,salicylic acid content and protein treating with F27.The results showed that compound F27 can enhance chlorophyll content,photosynthetic rat,defense enzymes activity and regulate the change of protein,further functional analysis of differential protein revealed F27 can improve photosynthesis of tobacco.So,compound F27 has excellent inhibitory activity against TMV is due to combined effects on inhibition of virus infection and activating resistance of the host.