Antimicrobial activity and cytotoxicity towards cancer cells of Melaleuca alternifolia (tea tree) oil

Antimicrobial and in vitro anti-tumor activities of Melaleuca alternifolia (tea tree) oil (TTO) were analyzed. The results indicated that TTO possessed significant antimicrobial activity towards all tested microorganisms except Aspergillus niger. The minimum inhibitory concentration (MIC) of TTO towards Staphylococcus epidermidi, Bacillus subtilis, Escherichia coli and Candida albicans was 0.25% (v/v). Time kinetic experiments showed that Staphylococcus epidermidi, Escherichia coli and Candida albicans were completely killed after exposure to TTO at 2x MIC for 1, 4 and 8 h, repectively. TTO also exhibited strong cytotoxicity towards human lung cancer cell line (A549), human breast cancer cell line (MCF-7) and human prostate cancer cell line (PC-3). The IC50 values obtained were 0.012% (v/v), 0.031% (v/v) and 0.037% (v/v), respectively. Flow cytometric analysis demonstrated that TTO restrained the cell cycle progression of PC-3 and MCF-7 cell lines at the G0/G1 phase and A549 cell at the S phase.