Screening of antimicrobial and antioxidant activity of commercial Melaleuca alternifolia (tea tree) essential oils

Abstract

The paper deals with the investigation of the chemical composition, antimicrobial and antioxidant activity of four commercial products of Melaleuca alternifolia essential (TTO). The chemical composition was determined using gas chromatography mass spectrometry (GC/MS) analysis. The broth-microdilution method was used to test antimicrobial activity. The antioxidant activity was tested by stable free radical of the 2,2-diphenyl-1-picrylhydrazyl (DPPH). Results of the chemical analysis identified over 30 components. The composition of the four samples varied and the major components included the following: terpinen-4-ol, γ γ γ γ-terpinene and α α α α-terpinene, respectively. The samples were compliant to the ISO Standard 4730. All TTOs presented similar degrees of antimicrobial activity. A slightly higher activity was shown by TTO 4 , having a balanced level of the three main components: terpinen-4-ol (34.58%) γ γ γ γ-terpinene (9.89%) and α α α α-terpinene (12.59%). Fungi were more sensitive than bacteria and yeast. All TTOs tested possessed the concentration-dependent antioxidant activity. Antioxidant activity was based on a balanced chemical composition between terpinen-4-ol and terpenic compounds. Biological testing confirmed the TTO antimicrobial activity against a wide range of the Gram-positive and Gram-negative bacteria, and fungi and yeasts. The correlation between the chemical composition and biological activity was quite evident. In conclusion, this study's results reveal not only the biological activity of TTO, but also its potential as an antioxidative agent.