紫云英苷对大肠杆菌的抑制作用及其机制研究

The Inhibitory Effect of Astragalin on Escherichia coli and Its Mechanism

【目的】初步测定4种辣木多酚单体成分(紫云英苷、绿原酸、芦丁和金丝桃苷)对大肠杆菌(Escherichia coli)的抑制作用,并以效果最好的紫云英苷为例,进一步探究其作用机制,以期为紫云英苷应用于食品防腐提供理论依据。【方法】采用二倍稀释法测定4种辣木多酚单体对大肠杆菌的半数抑制浓度(half maximal inhibitory concentration,IC50);通过生长曲线测定、结晶紫染色、核酸泄漏、蛋白质泄漏及扫描电镜探究紫云英苷对大肠杆菌生长、生物被膜及壁膜损伤的影响。【结果】4种辣木多酚单体对大肠杆菌均具有抑制作用,且呈剂量依赖性;其IC50值大小依次为金丝桃苷(676μmol/L)>绿原酸(605μmol/L)>芦丁(588μmol/L)>紫云英苷(490μmol/L)。经紫云英苷处理后的大肠杆菌生长明显受到抑制,生物膜形成及生物膜粘附性显著或极显著降低(P<0.05或P<0.001);细胞膜通透性极显著增加(P<0.001),导致生物大分子物质核酸和蛋白质泄漏;菌体出现表面褶皱、塌陷等严重变形现象。【结论】本研究初步揭示了紫云英苷对大肠杆菌的抑菌机制,对植物源天然抑菌剂的开发具有一定的意义。

[Purpose]The inhibitory effects of four monomeric components of Moringa oleifera polyphenols(astragalin,chlorogenic acid,rutin and hyperoside)on Escherichia coli were initially determined,and the most effective astragalin was used as an example to further investigated its mechan-ism,in order to provide a theoretical basis for the application of astragalin in food preservation.[Methods]The half-maximal inhibitory concentrations(IC50)of four M.oleifera polyphenols on E.coli were determined by the two-fold dilution method.The effects of astragalin on the growth,biofilm,and wall membrane damage of E.coli were investigated by growth curve,crystalline violet staining,nucleic acid leakage,protein leakage,and scanning electron microscopy.[Results]The four M.oleifera polyphenols had inhibitory effects on E.coli in a dose-dependent manner.The IC50 values of hyperoside,chlorogenic acid,rutin and astragalin were 676,605,588 and 490μmol/L,re-spectively.The growth of E.coli treated with astragalin was obviously inhibited,and biofilm forma-tion and biofilm adhesion were significantly or extremely significantly reduced(P<0.05 or P<0.001);cell membrane permeability was extremely significantly increased(P<0.001),leading to leakage of biomolecules including nucleic acids and proteins,and E.coli showed serious deformation such as surface folding and collapse.[Conclusion]This study initially reveals the mechanism of inhibition of E.coli by astragalin,which has some significance for the development of natural antibacterial agents of plants.