Antibacterial Synergism of Blended Essential Oils from Piper betle L. and Melaleuca alternifolia

Abstract

Aims: To investigate the synergistic antibacterial effects of blended essential oils from Piper betle and Melaleuca alternifolia against nine different bacterial strains. Methodology: GC-MS was employed for the analysis of essential oil extracted by hydro-distillation. The synergistic antibacterial effects of blended essential oils from Piper betle and Melaleuca alternifolia against nine different microbial strains were assayed using standard methods including disc diffusion, agar dilution and checkerboard. Results: The GC-MS analysis indicated the presence of 13 and 12 chemical compounds for the Piper betle and Melaleuca alternifolia essential oil, respectively. Essential oil from Piper betle consisted mainly of eugenol (39.21%) followed by other components: eugenol acetate (16.42%), 4-allyl-1,2-diacetoxybenzene (12.24%), terpinen-4-ol (6.58%), α-cadinol (6.13%), γ-terpinene (3.46%), and sabinene (2.14%). Meanwhile, the major components of tea tree essential oil were terpinen-4-ol (49.62%), followed by other components: γ-terpinene (18.08%), α-terpinene (9.16%), p-cymene (5.89%), α-terpineol (4.94%), terpinolene (3.47%), and α-pinene (2.02%). The synergistic antibacterial effects of blended essential oils from Piper betle and Melaleuca alternifolia were recorded in seven of the nine bacteria tested, including  Bacillus subtilis (FICI = 0.250%), Enterococcus faecalis (FICI = 0.375%), Staphylococcus aureus  (FICI = 0.313%), Methicillin-resistant Staphylococcus aureus  (FICI = 0.281%), Acinetobacter baumannii (FICI = 0.375%), Escherichia coli (FICI = 0.375%) and  Salmonella sp (FICI = 0.375%). However, additive effects were only observed in both Gram-negative bacteria including Klebsiella pneumoniae and Pseudomonas aeruginosa when treated with blended essential oils resulting in FICI value of 0.625% and 0.750%, respectively. Conclusion: The combination of essential oils from Piper betle and Melaleuca alternifolia exhibited more significant antibacterial effects against nine studied bacterial strains than single essential oil. Accordingly, the synergistic antibacterial effects were recorded in seven of the nine bacterial strains tested, whereas the additive effects were only observed in both Gram-negative bacteria.