The chemical compositions of seven essential oils from Taiwan were analyzed by gas chromatography-mass spectrometry. The eluates were identified by matching the mass fragment patents to the National Institute of Standards and Technology (NIST) 08 database. The quantitative analysis showed that the major components of lemon verbena are geranial (26.9%) and neral (23.1%); those of sweet marjoram are γ-terpinene (18.5%), thymol methyl ether (15.5%), and terpinen-4-ol (12.0%); those of clove basil are eugenol (73.6%), and β-(Z)-ocimene (15.4%); those of patchouli are carvacrol (47.5%) and p-cymene (15.2%); those of rosemary are α-pinene (54.8%) and 1,8-cineole (22.2%); those of tea tree are terpinen-4-ol (33.0%) and 1,8-cineole (27.7%); and those of rose geranium are citronellol (28.9%) and 6,9-guaiadiene (20.1%). These components are somewhat different from the same essential oils that were obtained from other origins. Lemon verbena has the same major components everywhere. Tea tree, rose geranium, and clove basil have at least one major component throughout different origins. The major components and their amounts in sweet marjoram, patchouli, and rosemary vary widely from one place to another. These results demonstrate that essential oils have a large diversity in their composition in line with their different origins. The antibacterial activity of essential oils against Escherichia coli was evaluated using the optical density method (turbidimetry). Patchouli is a very effective inhibitor, in that it completely inhibits the growth of E. coli at 0.05%. Clove basil and sweet marjoram are good inhibitors, and the upper limit of their minimum inhibitory concentration is 0.1%.
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