Chemical composition of Pistacia vera L. oleoresin and its antibacterial, anti-virulence and anti-biofilm activities against oral streptococci, including Streptococcus mutans

Objective The aim of this study was to characterise the chemical composition of oleoresin of Pistacia vera L. and to determine its antimicrobial and anti-virulence activity versus selected oral streptococci. Design A gaschromatografic analysis of the oleoresin was performed. The antimicrobial and anti-virulence activity of the oleoresin and its fractions was evaluated by the Minimum Inhibitory Concentration (MIC) and/or Minimum Bactericidal Concentration (MBC), biofilm production and haemolytic activity inhibition experiments. Results The oleoresin MBCs were >=1024 ?g/mL for all tested strains; the neutral and acidic fraction MBCs ranged from 128 to 2048 ?g/mL. Essential oil's MBCs (from 256 to 2048 ?g/mL) were almost identical to MICs, suggesting a bactericidal effect.P. vera oleoresin at sub-lethal concentrations significantly reduced biofilm production by Streptococcus mutans (up to 49.4%) and by Streptococcus sanguinis (up to 71.2%). In addition, the acidic fraction showed a specific anti-biofilm activity against S. mutans (up to 41.3% reduction). A significant dose-dependent reduction in the haemolytic activity of S. mutans (up to 65.9%) and of S. anginosus (up to 78.3%) was observed after growth in the presence of oleoresin at sub-lethal concentrations. The acidic fraction reduced haemolytic activity (up to 54.3% at 64 µg/mL) of S. mutans only. Conclusions Given the anti-virulence activity of theP. vera oleoresin and its acidic fraction against S. mutans, our findings suggest their potential use in oral hygiene. These data represent the first step in the exploitation of P. vera L. oleoresin.