In Vitro Evaluation of the Antimicrobial and Immunomodulatory Activity of Culinary Herb Essential Oils as Potential Perioceutics

Abstract

Due to their antimicrobial, immunomodulatory, antioxidant, and regenerative activities, culinary herbs have multiple medicinal uses, among which to prevent and treat oral diseases. The whole essential oils (EOs) have multiple advantages over purified components, such as a low probability to select for antimicrobial resistance, synergic effects of different components, and multi-pharmacological activities. In this study, we aimed to evaluate essential oils from Salvia officinalis (sage), Satureja hortensis (summer savory), and Anethum graveolens (dill) using an in vitro analysis of their antimicrobial activity against Gram-positive and Gram-negative bacterial strains isolated from the oral cavity of patients with periodontitis; the assays addressed both the planktonic and biofilm growth states and used culture-based approaches. Some of the tested EOs exhibited excellent bactericidal and antibiofilm activity, being active at concentrations as low as 0.08-1.36 mg/mL. Flow cytometry was used to investigate the potential mechanisms of their antibacterial activity and confirmed that the tested EOs act by permeabilizing the bacterial membrane and by inhibiting the activity of the efflux pumps. The immunomodulatory effect of the three EOs was determined by analyzing the gene expression profiles for pro- and anti-inflammatory cytokines of the THP-1 cells. The summer savory EO induced a clear proinflammatory effect, while the others did not significantly influence the cytokines profile of the tested cells. Taken together, our results indicate that summer savory EO and, to a lesser extent, sage and dill EOs could be used to inhibit bacteria involved in oral plaque formation and to reduce the expression of genes known to contribute to the inflammatory response using cell culture assessment.

Keywords: antimicrobial activity; cytotoxicity; essential oils; perioceutics; periodontal disease.

Figure 1

Histograms for Streptococcus salivarius sp. salivarius (panel A) and S. acidominimas (panel B) treated with volatile oils or analytical standard (β-pinene) vs. a viable cell control (marked with propidium iodide (PI) (red) and ethidium bromide (EB) (orange)).

Figure 2

Cytokine expression in THP-1 cells treated with essential oils (EOs) extracted from Salvia officinalis (sage), Satureja hortensis (summer savory), and Anethum graveolens (dill). n = 3 (t-test) and control—unstimulated cells. (A): expression of IL-10; (B): expression of IL-6; (C): expression of IL-1β; (D): expression of TNF-α. *, significant difference p < 0.05.