Chemical composition and antimicrobial activity of several typical essential oils

Abstract:

[Objective] Essential oils are aromatic oily liquids obtained from some aromatic plant materials by distillation and squeezing. In recent years, essential oils have attracted more attention due to their antimicrobial activity. The objective of this study was to analyze the chemical constituents and the antimicrobial activity of essential oils, and the correlation between them. [Methods] Six typical essential oils were selected as experimental target, including cassia oil, litsea cubeba oil, clove oil, citronella oil, rosemary oil and garlic oil. Then the chemical compositions of the above oils were analyzed by GC-MS. Moreover, the antifungal activity against Aspergillus niger and Penicillium funiculosum, and the antibacterial activity against Escherichia coli and Staphylococcus aureus were investigated with poisoned food technique. [Results] GC-MS analyses showed that the chemical composition of cassia oil, litsea cubeba oil, citronella oil, and rosemary oil were all mainly aldehydes and alcohols, the main composition of clove oil was eugenol. Garlic oil was composed of a variety of thio ethers; especially di-2-propenyl trisulfide (allicin) was the highest content in them. The poisoned food technique results revealed that different kinds of essential oil have diffident antimicrobial activities. The antifungal activity order of six essential oils was: cassia oil (highest activity) >garlic oil>clove oil>litsea cubeba oil=citronella oil>rosemary oil, and the antibacterial activity order was: cassia oil (highest activity) >litsea cubeba oil>clove oil>citronella oil=rosemary oil>garlic oil. [Conclusion] The antimicrobial activity of essential oils was closely related to their composition. The high efficient antimicrobial activity of cassia oil, litsea cubeba oil, citronella oil and rosemary oil is possible due to the composition of aldehydes and alcohols; antimicrobial activity of clove oil is result from the composition eugenol; and the high antifungal activity of garlic oils should be related to the composition of thio ethers. The different effective compositions in different essential oils suggest that different oils have different antifungal/antibacterial mechanism.