Unravelling the Complex Antimicrobial Interactions of Essential Oils — The Case of Thymus vulgaris (Thyme)

Abstract

Abstract:Thymus vulgaris has gained tremendous popularity as an ornamental, culinary herb and its use in phytotherapy is well established and supported in the literature. The objective of this study was to explore possible interactions between selected molecules within Thymus vulgaris essential oil (TvEO) to gain a better understanding of how this complex essential oil exerts its antimicrobial activity. Evaluation of the antimicrobial efficacy and interactions were assessed on the essential oil and volatile constituents against various pathogens. Interactions between molecules at various ratios were graphically observed through the construction of isobolograms. Gas chromatography-mass spectrometry (GC-MS) analysis revealed 22 compounds which collectively represent >95% of the oil composition. Based on their minimum inhibitory concentration (MIC) values, they were categorised into weak (≥4 mg mL ) and noteworthy active (≤2 mg mL −1 ) compounds. For the combination study, 21% synergistic, 42% additive, 36% indifferent and 1% antagonistic interactions were observed. Most of the interactions were observed between the weak and highly active molecules, and interestingly, no synergistic interaction was observed between the highly active compounds. Synergistic and additive interactions between the strong and weaker antimicrobial constituents present in TvEO enhance the antimicrobial efficacy of this commercially important essential oil.

The in vitro antimicrobial activity of Cymbopogon essential oil (lemon grass) and its interaction with silver ions

“…tuber-303 culosis, malaria etc. The main aim of combination therapy is to achieve 304 synergy, reducing drug dosage and minimizing or delaying the onset 305 of drug resistance (Van Vuuren and Viljoen 2011; Ahmad et al 2014). 306 The differences in chemical compositions of the CEO, irrespec-307 tive of qualitative and/or quantitative differences with the previously 308 published papers, restrict the validity of these interesting biologi-309 cal results to the CEO's with similar chemical compositions.…”

Combined effect of conventional antimicrobials with essential oils and their main components against resistant Streptococcus suis strains

“…These differences could be explained by the variety of mechanisms of action attributable to the essential oil compounds and the possible synergistic effect between them (Ahmad et al . ; Said et al . ).…”

“…7.0 software (GraphPad Software, Inc. California, CA) to present the FIC index of the combinations (Ahmad et al . ).…”

“…Isobolograms were plotting using GraphPad Prism, ver. 7.0 software (GraphPad Software, Inc. California, CA) to present the FIC index of the combinations (Ahmad et al 2014).…”

Screening of Thymus Vulgaris Essential Oil Against Fungi Causing Dermatophytosis in Human Beings

“…It is believed that the hydroxyl group on these compounds interact on the cytoplasmic membrane and changes its permeability by affecting lipid ordering and stability of its bilayer. Therefore proton passive flux across the membrane increased, which disrupted the cytoplasmic membrane and leading to leakage of cellular contents [35][36][37][38]. Antifungal activity of the essential oil of T. vulgaris L. and Thymol on experimentally induced dermatomycoses was carried out by Sokovi et al [29] and found excellent results.…”