Chemical profile of leaf essential oils from four Eucalyptus species from Thailand and their biological activities

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.