Design,Synthesis And Pharmacodynamic Study Of New Pyrazolines As Antibacterial Synergistic Agent

Antimicrobials play an important role in the prevention and treatment of bacterial infectious diseases.Antimicrobials can not only reduce the incidence of bacterial infectious diseases,but also save millions of lives from bacterial infections.With the widespread application of antimicrobials in clinic all over the world,the bacterial drug-resistance is emerged and spreaded and the anti-infective therapy face more and more serious chanlenges from drug-resistace pathogenic microorganisms.The development of new and efficient Antimicrobials is one of important way to against drug-resistance pathogenic microorganisms.However,due to the long new drug development duration and the limit anti-bacterial spectrum of drug-resistance pathogenic microorganisms,so the new anti-infective drugs can not keep up with the speed of the spread of drug-resistance pathogenic bacterials,and left gap in the clincal therapy of anti-infective.Therefore,it is necessary to explore and develop new way to fill up the gap.Antimicrobial synergists are the potential good chioces to solve the problem of drug-resistance.Antimicrobial synergists can inhibit the relavent drug-resistance mechanism,and enhance the antimicrobial activity of existing Antimicrobials,which can expand the range of existing antibacterial drug to drug-resistance pathogenic bacterials.In recent years,the development of antimicrobial synergistic drugs attract more and more attention in the anti-infective therapy.The main research contents of this subject are as follows:1.Design of target compounds:Two typical efflux pump proteins of bacterial multidrug resistance were selected as target proteins:(1)MFS superfamily transporter of E.coli facilitator(2)ABC superfamily transporter of Staphylococcus aureus.Based on the known basic skeleton of natural chalcones with broad antimicrobial activity,Computer molecular design and virtual screening were used to choose the leading structures and substitution fragment.The pyrazole rings and aliphatic carbon chains were introduced.Finally,four series of 24 new compounds were designed.Then these compounds were docked with target proteins to predict their biological activity.The results show that the scores of most of the small molecular compounds designed by us are more than or equal to 5,which indicated that they had good binding ability with ligand proteins.2.Synthesis of target compounds:The first step,using pyrrole,furan,thiophene and other five-membered heterocycles as starting materials,2-acetyl five-membered heterocycles were synthesized by Friedel-Crafts reaction.The second step,chalcones were synthesized from 2-acetyl pentacyclic heterocycles and p-methylpiperazine benzaldehyde by Claisen-Schmidt Condensation under strong base catalysis.The three step,chalcone analogues,hydrazine hydrate and aliphatic carboxylic acid were successively added in one-pot synthesis procedures.The target compounds was synthesized by Michael and nucleophilic addition and acylation,Twenty-two new pyrazole compounds were synthesized and their structure were characterized by 1H and 13 C NMR.3.Pharmacodynamic studies of target compounds:We screened the synergistic antimicrobial activities of the target compounds designed and synthesized.Firstly,the drug-resistant models of tetracycline-resistant Escherichia coli and levofloxacin-resistant Staphylococcus aureus were established by induction,and then MTT experiments of the target compounds and drug-resistant bacteria were carried out by chessboard method.The results showed that some of the target compounds had certain antimicrobial synergistic activity,and the synergistic activity of the target compounds against tetracycline-resistant Escherichia coli was better than that of levofloxacin-resistant Staphylococcus aureus.The antibacterial synergistic activity table showed that the compounds of LZ-C-5,LZ-C-6 and LZ-B-4,LZ-B-5 can reduce the MIC of tetracycline against tetracycline-resistant E.coli to eight times,LZ-D-6 and LZ-B-6 can promote tetracycline to reduce the MIC of tetracycline-resistant E.coli to four times.All the above compounds showed good synergistic effect against bacteria.In summary,a series of new pyrazole derivatives were derived by computer molecular simulation and synthesized by organic synthesis.The results showed that four leading compounds with potential antimicrobial synergistic activity were evaluated through pharmacodynamic studies,which is helpful to develop new bacterial efflux pumps in future.