Essential oil components and antibacterial effects of Eucalyptus robusta families

In order to screen for essential oil families of Eucalyptus robusta with excellent antibacterial, the study focused on the leaves of four E. robusta families in Nanning and Wuxuan. Fresh leaves of 5-year-old E. robusta were collected for steam distillation essential oil extraction. The chemical components of the essential oils were identified, and their antibacterial activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi were measured. The extracted oil yield, component differences among families, regional response of family essential oils, and effects of essential oil components on antibacterial activity were explored. The results were as follows:(1)The essential oils of four families of E. robusta were mainly composed of 73.695% to 84.535% monoterpenoids with the main components being pinene, phellandrene and p-cymene. The α-pinene content in the family 1 content can reach up to 41.629%, Common components among E. robusta families included α-pinene, β-pinene, α-phellandrene, d-limonene, p-cymene, γ-terpinene, 4-terpineol, and α-terpineol. The 1,8-cineole chemotype of E.robusta had a low oil production rate.(2)The leaf essential oils of different E. robusta families had different responses to environmental changes. α-phellandrene, 1,8-cineole, d-limonene, α-terpineol and p-cymene were correlation components.(3)E. robusta essential oil exhibited antibacterial activity against E. coli, S. aureus, and S. typhi. Notably, family 3 of E. robusta showed higher activity against S. typhi than streptomycin. However, no antibacterial ability against P. aeruginosa was observed. An increase in alcohols, ketones, and aldehydes was beneficial for improving its antibacterial activity. In conclusion, E. robusta essential oil is mainly composed of monoterpenoids. Certain essential oil components are correlated, and there are common components among families. Increasing alcohols, ketones, and aldehydes is beneficial for improving the antibacterial activity of E. robusta essential oil. However, the 1,8-cineole chemotype of E. robusta has a low oil production rate, indicating a need for further breeding efforts. This study provides a theoretical basis for the selection and breeding of E. robusta essential oil and their application in spices or medicine.