Re-evaluating natural compounds for antimicrobial use: essential oils and their activity against Escherichia coli

Antibiotic resistance is becoming a significant global problem. Pharmaceutical companies are investing less in the development of new antibiotics, making basic research in this area increasingly important. Essential oils have emerged as promising natural alternatives due to their antimicrobial activity, including against multidrug-resistant bacteria, either alone or in synergy with antibiotics. The aim of our study was to investigate the antimicrobial activity of selected, lesser-explored essential oils against Escherichia coli , a clinically relevant pathogen [ 1 ] [ 2 ] [ 3 ]. We tested 20 commercially available essential oils, including Thymus vulgaris as a reference due to its well-established antimicrobial properties. Because essential oils do not diffuse well in hydrophilic media, the disc diffusion method proved unsuitable. Instead, we used a liquid growth medium to assess antibacterial activity. Chemical composition of the essential oils was determined using gas chromatography-mass spectrometry (GC-MS). The essential oil of Thymus vulgaris contained 50% thymol, 18% para -cymene, 7% γ-terpinene, and 4% linalool and exhibited the strongest antimicrobial effect. Although none of the tested oils surpassed T. vulgaris , several showed notable antimicrobial activity, including Aniba rosaeodora (86% linalool, 4% eucalyptol), Pimenta officinalis (72% eugenol, 13% methyl eugenol, 8% caryophyllene ( E )), Eugenia caryophyllata (85% eugenol, 7% eugenyl acetate, 6% caryophyllene ( E )), and Evernia prunastri (100% methyl atrarate). Our results suggest that essential oils hold unexplored potential as antimicrobial agents. Future research should explore the effects of individual essential oil components, synergistic interactions, and their potential use in combination with antibiotics. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany