Antibacterial Properties of Polyphenols: Characterization and QSAR (Quantitative Structure–Activity Relationship) Models

Abstract

Besides their established antioxidant activity, many phenolic compounds may exhibit significant antibacterial activity. Here, the effect of a large dataset of 35 polyphenols on the growth of 6 foodborne pathogenic or food-spoiling bacterial strains, three Gram-positive ones ( Staphylococcus aureu s, Bacillus subtilis , and Listeria monocytogenes ) and three Gram-negative ones ( Escherichia coli, Pseudomonas aeruginosa , and Salmonella Enteritidis), have been characterized. As expected, the effects of phenolic compounds were highly heterogeneous ranging from bacterial growth stimulation to antibacterial activity and depended on bacterial strains. The effect on bacterial growth of each of the polyphenols was expressed as relative Bacterial Load Difference (BLD) between a culture with and without (control) polyphenols at a 1 g L −1 concentration after 24 h incubation at 37°C. Reliable Quantitative Structure-Activity Relationship (QSAR) models were developed (regardless of polyphenol class or the mechanism of action involved) to predict BLD for E. coli, S . Enteritidis, S. aureu s, and B. subtilis , unlike for L. monocytogenes and P. aeruginosa . L. monocytogenes was generally sensitive to polyphenols whereas P. aeruginosa was not. No satisfactory models predicting the BLD of P. aeruginosa and L. monocytogenes were obtained due to their specific and quite constant behavior toward polyphenols. The main descriptors involved in reliable QSAR models were the lipophilicity and the electronic and charge properties of the polyphenols. The models developed for the two Gram-negative bacteria ( E. coli, S . Enteritidis) were comparable suggesting similar mechanisms of toxic action. This was not clearly observed for the two Gram-positive bacteria ( S. aureu s and B. subtilis ). Interestingly, a preliminary evaluation by Microbial Adhesion To Solvents (MATS) measurements of surface properties of the two Gram-negative bacteria for which QSAR models were based on similar physico-chemical descriptors, revealed that MATS results were also quite similar. Moreover, the MATS results of the two Gram-positive bacterial strains S. aureus and B. subtilis for which QSARs were not based on similar physico-chemical descriptors also strongly differed. These observations suggest that the antibacterial activity of most of polyphenols likely depends on interactions between polyphenols and bacterial cells surface, although the surface properties of the bacterial strains should be further investigated with other techniques than MATS.

New SiO2/Caffeic Acid Hybrid Materials: Synthesis, Spectroscopic Characterization, and Bioactivity

“…However, the mechanism of action is not yet fully understood, as it could involve many sites at the cellular level. Several hypotheses were reported, including an altered permeability of cell membranes, the bond of phenolics to cell enzymes, and the disruption of membrane integrity, as they cause consequent leakage of essential intracellular constituents [38,39]. Also, the difference in antibacterial activity between Gram-positive and Gram-negative bacteria is still controversial in the literature.…”

High-polyphenol extracts fromSorghum bicolorattenuate replication ofLegionella pneumophilawithin RAW 264.7 macrophages

“…The majority of these studies have focused on food-borne pathogens, but reveal the potential for natural and sustainable sources of antimicrobial compounds. While in vitro restriction of many bacterial, fungal and viral pathogens has been evidenced (reviewed in [1,30,31]), polyphenols are also capable of specific inhibition of pathogen virulence. A striking example of this is the ability of tannic acid and n -propyl gallate to protect mice from Helicobacter pylori -mediated disease [32].…”

Middle Eastern Plant Extracts: An Alternative to Modern Medicine Problems

“…Compounds which belong to the phenol and terpene groups are known widely to have antimicrobial activity [6]. These phenolic compounds act on the bacteria by altering the permeability of the plasma membrane of bacterial cells, altering enzymes in the cells or through modifying the rigidity of the cell wall; this results in the loss of integrity in the cell membrane [79]. These are known to be irreversible cell damages.…”