Abstract Essential oils from four species of Eucalyptus plantation in northern Thailand (E. deglupta, E. urophylla, E. citriodora and E. camaldulensis) were compared for their chemical composition and antioxidant and antibacterial activity. The essential oil was distilled from fresh leaf samples of each species. The yield of essential oils was in the range 0.6–0.8% (v/w) for the different species. The chemical composition of the oil samples was analyzed using GC–MS. In total, 63 compounds were identified and the different chemical compound contents varied according to the species. E. deglupta, E. urophylla and E. camaldulensis was the richest species in eucalyptol and E. citriodora was the richest species in citronellal. The selected chemical components were analyzed using Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) and were able to clusterize in three groups based on relationships and chemical patterns in essential oils. The oils exhibited antioxidant and antibacterial activity varied significantly within plant species. E. citriodora oil showed the strongest antioxidant and antibacterial activity and can be a good candidate for the development of products for antioxidant and antibacterial activity among the four species tested. These results suggest Eucalyptus oil as a potent inhibitor of pathogenic microorganisms and oxidative stress. From this study, it may be concluded that the chemical composition in Eucalyptus oil depends upon the Eucalyptus species. The biological activity of Eucalyptus oil depends upon its chemical composition content. Currently, this is the first report on the comparison of chemical composition and biological activity of Eucalyptus essential oil from Northern Thailand.

中文翻译：

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泰国四种桉树叶精油的化学特征及其生物活性

摘要 比较了来自泰国北部四种桉树种植园的精油（E. deglupta、E. urophylla、E. citriodora 和 E. camaldulensis）的化学成分以及抗氧化和抗菌活性。精油是从每个物种的新鲜叶子样品中蒸馏出来的。不同物种的精油产量在 0.6-0.8% (v/w) 范围内。使用 GC-MS 分析油样的化学成分。共鉴定出 63 种化合物，不同的化合物含量因物种而异。E. deglupta、E. urophylla 和 E. camaldulensis 是桉树脑中含量最丰富的物种，E. citriodora 是香茅醛含量最丰富的物种。使用主成分分析 (PCA) 和层次聚类分析 (HCA) 对选定的化学成分进行分析，并能够根据精油中的关系和化学模式将其分为三组。这些油在植物物种中表现出的抗氧化和抗菌活性差异很大。E. citriodora oil 显示出最强的抗氧化和抗菌活性，可以成为四种测试物种中抗氧化和抗菌活性产品开发的良好候选者。这些结果表明桉树油是病原微生物和氧化应激的有效抑制剂。从这项研究中，可以得出结论，桉树油中的化学成分取决于桉树的种类。桉树油的生物活性取决于其化学成分含量。目前，这是泰国北部桉树精油化学成分和生物活性比较的首次报道。