Multivariate Characterization of Essential Oils for Their Antibacterial Activity Against Escherichia coli: A Data-Driven Interpretation of Experimental Results

The growing problem of antimicrobial resistance emphasizes the urgent need for new and effective natural antimicrobial agents. This study assessed the antibacterial activity of twenty essential oils and one absolute against <i>Escherichia coli</i> and examined the relationship between their chemical composition and biological activity. The chemical profiles of the samples were determined using gas chromatography-mass spectrometry (GC-MS), and the resulting data were analysed using principal component analysis (PCA), discriminant analysis (DA), and partial least squares (PLS) methods to explore associations between composition and antibacterial activity. The results showed substantial variability among the tested essential oils, with those from <i>Thymus vulgaris</i>, <i>Aniba rosaeodora</i>, <i>Syzygium aromaticum</i>, <i>Pimenta dioica</i>, and the absolute of <i>Evernia prunastri</i> exhibiting the strongest activity. GC-MS analysis identified thymol, eugenol, and methyl atrarate as key bioactive constituents associated with strong antibacterial effects, while linalool, limonene, and α-terpineol were linked to moderate activity. Multivariate analyses provided further insight but were limited by data variability, highlighting compositional diversity rather than clear group separation. Overall, the findings demonstrate that essential oils are a promising source of natural antimicrobial agents and emphasise the importance of linking chemical composition with biological function to understand their potential therapeutic applications.