Antioxidant and anti-inflammatory properties of essential oils from three Eucalyptus species
Authors:   Department of Medical Technology, School of Allied Health Sciences, University of Phayao, Phayao 56000, Thailand, Insuan Orapin ,   Unit of Excellence in Integrative Molecular Biomedicine, School of Allied Health Sciences, University of Phayao, Phayao 56000,  Thailand, Thongchuai Benchaluk ,   Department of Medical Technology, School of Allied Health Sciences, University of Phayao, Phayao 56000, Thailand,   Unit of Excellence in Integrative Molecular Biomedicine, School of Allied Health Sciences, University of Phayao, Phayao 56000,  Thailand, Chaiwongsa Rujirek ,   Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand, Khamchun Supaporn ,   Department of Medical Technology, School of Allied Health Sciences, University of Phayao, Phayao 56000, Thailand,   Unit of Excellence in Integrative Molecular Biomedicine, School of Allied Health Sciences, University of Phayao, Phayao 56000,  Thailand, Insuan Wimonrut ,   Department of Veterinary Technology, Faculty of Veterinary Technology, Kasetsart University, Bangkok 10900, Thailand
Published: September 2021

Abstract Eucalyptus essential oils are used as traditional medicines in many countries. The objective of this study was to evaluate the antioxidant and anti-inflammatory activities of leaf essential oils extracted from three different Eucalyptus species on HepG2 and RAW264.7 cells. Essential oils were distilled from fresh leaf samples, and the chemical constituents were analyzed using gas chromatography–mass spectrometry. The antioxidant activities of essential oils were determined using ABTS and hydroxyl radical scavenging assays, and hydrogen peroxide (H2O2)-induced oxidative stress in HepG2 cells. Additionally, lipopolysaccharide (LPS)-activated RAW264.7 macrophages were used to evaluate the anti-inflammatory properties. The results revealed that Eucalyptus citriodora and Eucalyptus urophylla leaf essential oils had a high content of oxygenated monoterpenes, whereas Eucalyptus deglupta contained a high amount of monoterpene hydrocarbons. Essential oils extracted from the three Eucalyptus species showed antioxidant and anti-inflammatory activities. E. citriodora and E. urophylla leaf essential oils had strong antioxidant activity against H2O2-induced oxidative stress in human HepG2 cells. Additionally, E. citriodora leaf essential oil, which contains a high amount of citronellal, exhibited the most potent anti-inflammatory activity in LPS-activated RAW264.7 macrophages. The antioxidant and anti-inflammatory effects of essential oils depended on their chemical composition. A principal component analysis explained 100% of the variance was performed to construct three groups based on the chemical components and antioxidant and anti-inflammatory activities. This study suggests that E. citriodora leaf essential oil, which represents a good source of oxygenated monoterpenes, could be considered a potential phytochemical agent for the prevention of oxidative stress and inflammation. Keywords: Antioxidant, Anti-inflammatory effect, Eucalyptus essential oils, Gas chromatography–mass spectrometry, Principal component analysis