Chemical composition and biological evaluation of tea tree (Melaleuca alternifolia L.) leaves essential oils

Melaleuca alternifolia L. essential oils (MaEO), extracted through steam, distillation of its leaves, offer a multitude of benefits. The aim of the study was to determine the physicochemical and biological properties, such as relative density, absolute density, acid value, saponification value, ester value, freezing point, fragrance retention, antioxidant and antibacterial activity of MaEO. Gas chromatography-mass spectrometry (GC-MS) analysis was used to analyze the chemical composition of essential oils (EO), and the obtained results displayed those 45 compounds were identified and quantified; among them, the main component was Terpinen-4-ol (44.55%). In addition, the antioxidant capacity (AC) was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay with the half maximal inhibitory concentration (IC) of 360 mg mL. Moreover, MaEO also had excellent antibacterial activity (AA) against certain types of bacteria, using the paper disc diffusion method for antibiotic susceptibility testing. The diameter of the inhibitory zones were 12.33, 14, 15.67, and 24.33 mm for Bacillus cereus (ATCC 11778), Staphylococcus aureus (ATCC 25923), Salmonella enterica (ATCC 13076), and Escherichia coli (ATCC 25922), respectively.