The Inhibitory Effect of Astragalin on Escherichia coli and Its Mechanism

PurposeThe 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 mechanism, in order to provide a theoretical basis for the application of astragalin in food preservation.

MethodsThe 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.

ResultsThe 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 490 μmol/L, respectively. The growth of E. coli treated with astragalin was obviously inhibited, and biofilm formation 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.

ConclusionThis 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.