The essential oil of clove has a wide range of pharmacological and biological activities and is widely used in the medicine, fragrance and flavoring industries. In this work, 22 components of the essential oil obtained from clove buds were identified. Eugenol was the major component (76.23%). The essential oil exhibited strong antibacterial activity against Staphylococcus aureus ATCC 25923 with a minimum inhibitory concentration (MIC) of 0.625 mg/mL, and the antibacterial effects depended on its concentration and action time. Kill-time assays also confirmed the essential oil had a significant effect on the growth rate of surviving S. aureus. We hypothesized that the essential oil may interact with the cell wall and membrane first. On the one hand it destroys cell wall and membranes, next causing the losses of vital intracellular materials, which finally result in the bacterial death. Besides, essential oil penetrates to the cytoplasmic membrane or enters inside the cell after destruction of cell structure, and then inhibits the normal synthesis of DNA and proteins that are required for bacterial growth. These results suggested that the effects of the clove essential oil on the growth inhibition of S. aureus may be at the molecular level rather than only physical damage.
Keywords: DNA; Staphylococcus aureus; alkaline phosphatase; electron microscope; essential oil; membrane permeability; protein.