Study On Antibacterial Activity Of Sophora Flavescens Ait In Vitro

Objective(s):1.To determine the in vitro antibacterial activity of the alcohol extracts from 23 Chinese herbal medicines such as Sophora flavescens Ait and the kind with stronger antibacterial activity were screened out.2.To track and separate the monomer compounds from the active extracts of Sophora flavescens Ait Their structures were identified and the in vitro antibacterial activity were further determined.3.To evaluate the in vitro antibacterial effects of the active compounds in combination with clinical commonly antibiotics.Methods:1.The monomer compounds were isolated and purified from active extracts of the Chinese herbal medicine through bioactivity-guided fractionation i.e.the antimicrobial susceptibility tests integrated with silica gel chromatography and other separation methods(including solvent extraction acid extraction and alkali precipitation.).The isolated compounds were identified by physicochemical methods and modern spectral techniques.2.The antibacterial activity of ethanol extracts,fractions and monomers were studied in vitro.The minimum inhibitory concentration(MIC)and the minimum bactericidal/fungicidal concentration(MB(F)C)were determined using by the standard broth microdilution method.According to the MIC/MB(F)C values,the checkerboard microdilution method and the time-killing curve method were used to evaluate the antibacterial effect of the monomer compound in combination with commonly used antibiotics.Results:1.Nine compounds were isolated from the ethyl acetate insolubles section,precipitation section with a pH value of 10,and the chloroform extract section with a pH of 10 of the Sophora flavescens Ait were identified as:sophoraflavanone G(1),kurarinone(2),kuraridin(3),7-hydroxy-4'-methoxyisoflavone(4),gentiobioside(5),formononetin-7-gentiobioside(6),trifolirhizin(7),salicylic acid(8)and hexadecanoic acid(9).The antibacterial activity of the isolated compounds showed that:salicylic acid,trifolirhizin,kurarinone,sophoraflavanone G showed antibacterial effects against standard Staphylococcus aureus and methicillin-resistant Staphylococcus aureus(MRSA),especially kurarinone and sophoraflavanone G showed moderate to significant antibacterial activity with the MIC/MBC values between 0.5?62.5?g/mL.2.The anti-MRSA activity of kurarinone in combination with conventional antibiotics by the checkerboard microdilution method showed that the combination of kurarinone and penicillin sodium was synergistic and additive against 3 strains and 1 strain,respectively.The combined action of kurarinone and ampicillin was synergistic and additive against 5 strains and 2 strains,respectively.The combination of kurarinone and piperacillin/tazobactam was synergistic and additive against 3 strains and 1 strain,respectively.The combination of kurarinone and imipenem/cilastatin was synergistic and additive against 3 strains and 1 strain,respectively.The combined action of kurarinone and ceftriaxone sodium was synergistic and additive against 2 strains and 2 strains,respectively.The combined action of kurarinone and amikacin was synergistic and additive against 5 strains and 2 strains,respectively.3.The MRSA strains with synergistic bacteriostatic action in the checkerboard test were further evaluated on their mode of combinatory bactericidal effect by the time-killing curve method.The results showed that for MRSA42,kurarinone combined with penicillin sodium at MIC and 1/2MIC,the mode of action is synergistic at 4 h;the combined action mode of kurarinone and ampicillin at MIC,1/2MIC,1/4MIC was synergistic at 12 h,12 h and 8 h,respectively.For MRSA70,the combined action mode of kurarinone with piperacillin/tazobactam was indifferent.For MRSA82,the combined action mode of kurarinone with ceftriaxone at MIC was additive at 24 h;the combined action mode of kurarinone with amikacin at MIC,1/2MIC and 1/4MIC was synergistic at 24 h,24 h and 12 h,respectively.For MRSA166,the combined action mode of kurarinone with penicillin sodium was indifferent;the combined action mode of kurarinone with ampicillin was synergistic;the combined action mode of kurarinone with imipenem/cilastatin at MIC,the mode was additive at 24 h;the combined action mode of kurarinone and amikacin was synergistic.For MRSA331,the combined kurarinone with penicillin sodium at MIC and 1/2MIC was synergistic;the combined action mode of kurarinone with penicillin sodium was indifferent.Conclusion(s):1.In this paper,the in vitro antimicrobial compounds against bacteria and fungi were investigated from the ethanol extract of Sophora flavescens Ait Nine compounds were isolated from the active sections i.e.,sophoraflavanone G,kurarinone,kuraridin,7-hydroxy-4'-methoxyisoflavone,gentiobioside,formononetin-7-gentiobioside,trifolirhizin,salicylic acid and hexadecanoic acid,among which the sophoraflavanone G and kurarinone showed strong antibacterial activity against Staphylococcus aureus.2.For MRSA42,the combined action mode of kurarinone and penicillin sodium and ampicillin was synergistic.For MRSA82,the combined action mode of kurarinone and amikacin was synergistic.For MRSA166,the combined action mode of kurarinone and ampicillin was synergistic.For MRSA331,the combined action mode of kurarinone and penicillin sodium and amikacin was synergistic.