Applied Microbiology

Biography

Biography: Amal Kamil Najjar

Abstract

Phenylpropenes (PPs) are volatile hydrophobic phytochemicals generally characterized by their potent antibacterial activities. The modes of antibacterial actions of these molecules differ from those of conventional antibiotics, which suggests their usage may help overcome antibiotic resistance mechanisms.The efficacy of allylic/propenylic PP isomers (eugenol/isoeugenol and estragole/anethole) was evaluated by macrodilution methods allowing to determine IC50s, MICs and MBCs against reference strains, Escherichia coli ATCC 25922 and Staphylococcus epidermidis ATCC 14990. Results indicate that all PPs were efficient against both bacteria in low millimolar levels, which makes them considerably less potent than common antibiotics. Allylic/propenylic isomers presented very similar growth inhibition patterns, indicating that the position of the double bond in the propenyl chain has low influence on PPs efficacy against the studied strains. For both strains, eugenol and isoeugenol were two to three times less effective than anethole and estragole, indicating distinctive modes of actions between these two pairs of isomers. Eugenol and isoeugenol would particularly involve their hydroxyl group to elicit antibacterial activity. Lacking a free hydroxyl group, the mode of action of anethole and estragole may be rather related to their higher lipophilic character. Interestingly, Gram-negative E. coli, showed to be more susceptible to all PPs than the Gram-positive S. epidermidis strain, probably due to the easier permeation of PPs across the hydrophobic cell emvelope structures of E. coli. Using high-dose PPs (low millimiolar levels) in vivo may not be an optimal strategy, however combination of phytochemicals presenting different mechanisms of action may allow reduction of efficient doses.