The significance of minor components on the antibacterial activity of essential oil via chemometrics

The significance of minor constituents of essential oils (EOs) for antibacterial activity by chemometric methods principal component analysis (PCA) and hierarchical clustering analysis (HCA) was researched. In this study, the antibacterial activity of six EOs from Achillea and Artemisia species was evaluated on nine laboratory control bacterial strains. Gas Chromatographic-Mass Spectrometric (GC/MS) data showed that these samples have similar chemical compositions, with highest content of oxygenated monoterpenes and lowest content of oxygenated sesquiterpenes and sesquiterpenes hydrocarbons. The strongest clustering is observed for Achillea millefolium and Achillea crithmifolia EOs. In PCA analysis, these two EOs are located at the considerable distance away from all of the other samples of EOs, indicating that their composition and activity differs significantly from the other samples. All bacteria for assessment of antimicrobial activity are grouped to the left side of the plot, located diametrically opposite to group I. This unique location can be pointed out as a reason for the lowest activity against bacteria, suggesting that the dominant EO components may not determine antibacterial activity. These findings were suggesting that the minor compounds (oxygenated sesquiterpenes and sesquiterpenes hydrocarbons) or a combination thereof were possibly responsible for the complete antibacterial activity of EOs. •The importance of essential oil minor components for antibacterial activity was done.•In study principal component analysis and hierarchical clustering analysis were used.•All studied essential oils contained predominantly oxygenated monoterpenes.•The minor compounds were oxygenated sesquiterpenes and sesquiterpenes hydrocarbons.•The minor compounds were possibly responsible for the antibacterial activity of EOs.