In vitro examination of antibacterial and immunomodulatory activities of cinnamon, white thyme, and clove essential oils

Abstract

The present study was conducted to evaluate the in vitro antimicrobial effect of three essential oils (cinnamon, white thyme, and clove) on selected intestinal pathogen bacteria, probiotic strains, and commensal bacteria. Additionally, their effects on inflammatory gene expression were also evaluated in a well-known intestinal human cellular model (Caco-2 cells). Cinnamon showed the highest antipathogenic microbial activity, followed by white thyme and clove. In the case of the probiotic strains, the inhibitory effect was observed at 0.1% (v/v), although growth recovery was seen after 24 h of incubation. Besides, cinnamon down-regulated the expression of genes related to the Toll-like receptor, nitric oxide, and apoptosis pathways. Similarly, secretion of interleukin 2 was inhibited by cinnamon. Results support the potential use of essential oils in the food industry for their antimicrobial and immunomodulatory effects; however, the underlying mechanisms are unknown and warrant further research.