Antibacterial activity and mechanism of pinoresinol from Cinnamomum Camphora leaves against food-related bacteria

Pinoresinol from the leaves of Cinnamomum camphora used as a model natural compound was extracted and isolated. The chemical characterization of the compound was confirmed using UV, IR, MS, H NMR and C HMR. The purity of the compound (86%) was determined using HPLC technique and it was used for further experiments. Its antibacterial activities against five food-related bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Salmonella enterica) were detected using both broth dilution method and disk diffusion method. Results indicated that 62.5 mu g/mL pinoresinol completely inhibit the growth of five bacteria. Much effort was focused on elucidating the mechanism of antibacterial action of pinoresinol against P. aeruginosa and B. subtilis by determination of cell permeability and observing the changes of cell microstructure using scanning electron microscope (SEM). The leakage of the soluble saccharides and proteins were detected and up to 13.89 and 21.76 mu g/mL, respectively for P. aeruginosa and 11.08 and 19.05 mu g/mL, respectively for B. subtilis. Measurements of the release of the soluble saccharides and proteins confirmed the disruptive action of pinoresinol on cytoplasmic membrane. The damages of the pinoresinol on cell wall were confirmed using Gram staining and scanning electron microscopy (SEM). We concluded that the antibacterial action mechanism of the pinoresinol is attributed to the physiological and morphological changes in bacterial cells. (C) 2017 Elsevier Ltd. All rights reserved.