In vitro antimicrobial potential of representative Mediterranean plant extracts against oral microorganisms

Bacteria, viruses, and fungi are capable of forming dynamic microbial networks, namely biofilms, on human substrata, causing numerous infectious diseases [1]. In the oral cavity, more than 700 microbial species have been recovered so far, resulting in the genesis of caries, gingivitis or periodontitis. Recent years have seen a focus in oral microbiology research on the elucidation and elimination of biofilm-related dental diseases [2,3]. The need to discover new efficient treatment strategies against oral microbial species has raised interest in novel therapeutic approaches. Especially the antimicrobial activity of natural products is highly acknowledged. The aim of the present study was to examine the antimicrobial potential of plant extracts of the Mediterranean against various microbial species. Representative genera of the Mediterranean were tested such as Cistus, Inula, Lavandula, Mentha, Origanum, Phlomis, Rosmarinus, Sideritis, Salvia, Satureja, Stachys and Thymus. Extracts were produced with accelerated solvent extraction and ultrasound assisted extraction using ethyl acetate and methanol/water 80:20, as the extraction solvents. Their profiles were generated using High Performance Thin Layer Chromatography revealing their high content in natural compounds. The extracts were screened against a panel of nine relevant pathogenic microorganisms, which constitute typical residents of the oral microflora, including one strain of Candida albicans. Additionally, Staphylococcus aureus and Escherichia coli, normally a part of skin and intestinal flora, served as reference bacterial strains. Two antimicrobial assays, the minimum inhibitory concentration (MIC) assay and the minimum bactericidal concentration (MBC) assay, were utilized. Extracts were less effective against C. albicans and exerted bactericidal effects at concentration range of 0.07 – 5.00 mg mL^-1 on strict anaerobic bacteria and could therefore be considered as alternative natural anti-infectious agents.

Keywords: Mediterranean, oral diseases, Cistus, Origanum, Sideritis.

References:

[1] Battin TJ, Sloan WT, Kjelleberg S, Daims H, Head IM, Curtis TP, Eberl L. Microbial landscapes: New paths to biofilm research. Nat Rev Microbiol 2007; 5: 76 – 81

[2] Al-Ahmad A, Wunder A, Auschill TM. The in vivo dynamics of Streptococcus spp., Actinomyces naeslundii, Fusobacterium nucleatum and Veillonella spp. in dental plaque biofilm as analysed by five-colour multiplex fluorescence in situ hybridization. J Med Microbiol 2007; 56: 681 – 687

[3] Karygianni L, Follo M, Hellwig E, Burghardt D, Wolkewitz M, Anderson A, Al-Ahmad A. Microscope-based imaging platform for large-scale analysis of oral biofilms. Appl Environ Microbiol 2012; 78: 8703 – 8711