Synergistic effects of cinnamaldehyde and cinnamic acid in cinnamon essential oil against S. pullorum

Abstract Cinnamon is an important spice crop that is widely cultivated in tropical regions. In this study, the antibacterial activities of four accessions of cinnamon essential oil (CEO) belonging to three different species (CEO1 and CEO4, Cinnamomum cassia Presl. (Lauraceae) bark; CEO2, Cinnamomum zeylanicum Blume (Lauraceae) bark; CEO3, Cinnamomum burmannii Blume (Lauraceae) bark) toward Salmonella enterica subsp. enterica serovar pullorum (S. pullorum) were evaluated by microdilution assay and kinetic analysis. The minimum inhibitory concentration (MIC) of the CEOs were all 0.31 mg/mL, and kinetic analysis suggested that the lag phase and maximum specific growth rate of bacteria were concentration dependent. Furthermore, to explore the synergistic antibacterial effects between main components and minor components, the volatile constituents of CEOs were determined by gas chromatography–mass spectrometry (GC–MS). Cinnamaldehyde (CM) (57.73 %–91.79 %) was the principal constituent in CEO1–CEO4 (p