The Active Compounds And Inhibition Mechanism Of Burdock Leaf Against Foodborne Pathogen Biofilm

Biofilm can protect bacterias to be killed by antibiotics or the immune system. Its mechanism of resistance is different from planktonic bacteria. This study is intended screening active ingredients in plant, and further to explore the mechanism of inhibition on bacterial biofilms.Different concentrations of ethanol eluted burdock leaf have inhibitory effect on biofilms. The crystal violet assay indicated 34% ethanol-eluted burdock leaf has better anti-biofilm activity on Salmonella typhimurium and Pseudomonas aeruginosa biofilm. 70% ethanol-eluted burdock leaf has the best anti-biofilm activity on Staphylococcus aureus biofilm, the inhibition rate is 100%at a concentration of 2 mg/m L.Then, the chemical composition of burdock leaf fraction was analyzed by UPLC-MS and 10 active compounds(chlorogenic acid, caffeic acid, p-coumaric acid, quercetin, ursolic acid, rutin,luteolin, crocin, benzoic acid, Tenacissoside I) were identified.UPLC-MS analysis was applied to obtain the metabolic fingerprints of standards before and after inhibiting the biofilm of Pseudomonas aeruginosa. The metabolic fingerprints were transformed to data with the software Marker Lynx, analyzed with PCA(principle component analysis) and PLS-DA(partial least squares discriminant analysis). Then, caffeic acid, rutin,coumarin and ursolic acid were identified as the anti-biofilm ingredients. The metabolic fingerprints of burdock leaf fractions were acquired before and after inhibiting the biofilm of Pseudomonas aeruginosa and Salmonella typhimurium. And 47 and 43 variables were screened as potential anti-biofilm ingredients in burdock leaf fractions. Chlorogenic acid, ursolic acid, caffeic acid,p-coumaric acid, rutin were identified to inhibit Pseudomonas aeruginosa biofilms. Chlorogenic acid and quercetin were identified and confirmed as potential anti-biofilm compounds among them.It provided data basic for the study of anti-biofilm compounds in burdock leaves, as well as provided a new and convenient method for fast screening o.f anti-biofilm ingredients from natural plants.Finally, made a preliminary research on the mechanism of burdock leaf fractions inhibiting Pseudomonas aeruginosa biofilm. Cell Surface hydrophobicity of bacteria, swaring motility,bacterial aggregation ability were measured when worked with burdock leaf fractions. They were all reduced after exposing by burdock leaf fractions. Thus, discussed the impact of 34% of burdock component on P. aeruginosa virulence factors and Quorum-Sensing System signal molecules3-oxo-C12-HSL, they were all reduced. These provide targets for plant active ingredients to inhibit biofilm.