Critical Synergistic Concentration of Lecithin Phospholipids Improves the Antimicrobial Activity of Eugenol against Escherichia coli

• Published in: Applied and environmental microbiology Vol. 83; no. 21
• Main Authors: Zhang, Haoshu, Dudley, Edward G, Harte, Federico
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.11.2017
• Subjects: Anti-Bacterial Agents - pharmacology; Antiinfectives and antibacterials; Antimicrobial activity; Antimicrobial agents; Cations; Chemical compounds; Deactivation; Drug Synergism; E coli; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - metabolism; Eugenol; Eugenol - pharmacology; Food Microbiology; Inactivation; L-Serine; Lecithin; Lecithins - pharmacology; Lipids; Microorganisms; Oils, Volatile - pharmacology; Phosphates; Phosphocholine; Phospholipids; Phospholipids - pharmacology; Properties (attributes); Reduction; Salts; Sodium; eugenol; lecithin; phospholipids; E. coli; monoterpenes
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.01583-17

In this study, the effect of individual lecithin phospholipids on the antimicrobial properties of eugenol against C600 was investigated. We tested five major phospholipids common in soy or egg lecithin (1,2-dihexadecanoyl-sn-glycero-3-phosphocholine [DPPC], 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine [DSPC], 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine [DPPE], 1,2-dihexadecanoyl-sn-glycero-3-phosphate [sodium salt] [DPPA], and 1,2-dihexadecanoyl-sn-glycero-3-phospho-l-serine [DPPS]) and one synthetic cationic phospholipid (1,2-dioctadecanoyl-sn-glycero-3-ethylphosphocholine [18:0 EPC]). Among the six phospholipids, DPPC, DSPC, DPPE, DPPA, and the cationic 18:0 EPC showed critical synergistic concentrations that significantly improved the inactivation effect of eugenol against after 30 min of exposure. At the critical synergistic concentration, an additional ca. 0.4 to 1.9 log reduction (ca. 0.66 to 2.17 log CFU/ml reduction) in the microbial population was observed compared to eugenol-only (control) treatments (ca. 0.25 log reduction). In all cases, increasing the phospholipid amount above the critical synergistic concentration (which was different for each phospholipid) resulted in antimicrobial properties similar to those seen with the eugenol-only (control) treatments. DPPS did not affect the antimicrobial properties of eugenol at the tested concentrations. The critical synergistic concentration of phospholipids was correlated with their critical micelle concentrations (CMC). Essential oils (EOs) are naturally occurring antimicrobials, with limited use in food due to their hydrophobicity and strong aroma. Lecithin is used as a natural emulsifier to stabilize EOs in aqueous systems. We previously demonstrated that, within a narrow critical-concentration window, lecithin can synergistically enhance the antimicrobial properties of eugenol. Since lecithin is a mixture of different phospholipids, we aimed to identify which phospholipids are crucial for the observed synergistic effect. This research studied the bioactivity of lecithin phospholipids, contributing to a rational design in using lecithin to effectively control foodborne pathogens in foods.