Mechanisms of bactericidal action of Eugenol against Escherichia coli

Abstract

Bioactive compounds exhibit antimicrobial activity against diverse microbial pathogens and can be an alternative to antibiotics to avoid the increasing microbial antibiotic resistance. To understand the mechanism underlying the antibacterial activity, the present study was undertaken using the bioactive compound, eugenol. A wide range of antibacterial activity was demonstrated by eugenol against the test pathogens with MIC ranging from 0.0312 to 8 μg/mL. The corresponding MBC of the compound was 2-4 fold higher. Time kill curve revealed eugenol to effectively reduce E. coli to undetectable levels within 4 h. The compound demonstrated disruptive action on the cytoplasmic membrane as measured by intracellular ATP. An increase in MIC value of the compound in the presence of divalent cations and increased membrane depolarization of the bacterium was observed. The morphological and physiological changes in E. coli were also recorded through SEM and TEM studies. The present study suggests eugenol alters membrane permeability resulting in leakage of intracellular contents. This may further allow the drug to interact with the intracellular sites causing cell damage.