Optimisation and Formulation of Synergistic Essential Oil Combinations for Effective Antimicrobial Activity against Respiratory Pathogens

An antimicrobial study was conducted on 369 essential oil combinations commonly indicated for respiratory infections. Based on the findings, five distinct combinations of essential oils held promise having antimicrobial synergy, anti-inflammatory effects and retaining cell viability between 80.4% and 99.6% against A549 cells. This study aimed to quantify and optimize the synergy of all five combinations and select the optimum combination for further nanoemulsion formulation ideal for respiratory inhalation formulation. The prediction tool, SynergyFinder was implemented to determine optimal synergy blends. According to the synergy maps derived, and by means of computational interpretation, the best essential oil combination comprised of essential oils from Hyssopus officinalis var. angustifolius in combination with Salvia rosmarinus var. angustifolius, with a blend representing 49.57% of H. officinalis to 50.43% of S. rosmarinus. This optimized blend was then formulated into a nanoemulsion, using the two-component, self- emulsification technique. The essential oil nanoemulsion showed strong in vitro antimicrobial activities against pathogens of the respiratory tract including; Streptococcus pneumoniae (ATCC 49619), Haemophilus influenzae (ATCC 19418), Klebsiella pneumoniae (ATCC 13883) and Moraxella catarrhalis (ATCC 23246) with an average six-fold improvement in antimicrobial effect when compared to the neat essential oils when tested in minimum inhibitory assays. The blended H. officinalis and S. rosmarinus essential oil nanoemulsion therefore holds potential to be developed as a natural antimicrobial agent for the management of respiratory tract infections.

Publication History

Article published online:
16 November 2023