Composition and antimicrobial activity of essential oils of Salvia fruticosa and Salvia ringens (Lamiaceae)

Abstract

Background/Aim. Plant essential oils (EOs) can have a significant antibacterial effect especially through additive or synergistic action as antibiotic adjuvants. We investigated the composition and activity of EOs of two species of genus Salvia from Greece with an aim to evaluate their antimicrobial activity as well as the activity of essential oil in combination with selected antibiotics. Methods. The aerial parts of wild-growing S. fruticosa and S. ringens were subjected to a steam distillation and the obtained EOs were analyzed by gas chromatography and gas chromatography/mass spectrometry. The brothmicrodilution method was used in order to determine the minimum inhibitory concentrations (MICs) of essential oils on seven strains of bacteria and one yeast. The antimicrobial activity of the combination of essential oil and antibiotics was investigated by checkerboard method and estimated by calculating the fractional inhibitory concentration (FIC) of each component and the fractional inhibitory concentration index (FICI). Results. Dominant component of S. fruticosa essential oil was trans-thujone (54.2%), and for S. ringens essential oil it was α-pinene (28.1%). The MICs of essential oils of both species were in the range from 200 μg/ml to >500 μg/ml. The strongest antimicrobial effect was achieved against B. subtilis and C. albicans. According to FICI values essential oil of S. fruticosa had additive effect with ciprofloxacin against most of bacterial strains but not with amikacin. Conclusion. The essential oils of S. ringens and S. fruticosa showed modest antimicrobial activity, however essential oil of S. fruticosa showed a promising additive effect in combination with ciprofloxacin.

Chemometric Analysis Evidencing the Variability in the Composition of Essential Oils in 10 Salvia Species from Different Taxonomic Sections or Phylogenetic Clades

“…The results of this study are generally in agreement with those of previous studies examining the EO of S. ringens from Greece [65,66] (Supplementary Materials Table S2). However, there are important variations in terms of the relative percentages of the components.…”

“…More specifically, 1,8-cineole, α-pinene, bornyl acetate, and β-pinene were the main compounds of the EO in the first study [65]; it is noteworthy to mention that bornyl acetate was found in fewer amounts in all our analyzed samples, apart from src1. In the second study, α-pinene, β-pinene, 1,8-cineole, camphene, and borneol were detected as the dominant components [66]. Moreover, the major component of S. ringens EO from Bulgaria was camphor [67] (Supplementary Materials Table S2).…”