Synthesis of some Thymol derivatives for enhanced antibacterial activity

Thymol derivatives were synthesized by condensation reactions implicating its phenolic hydroxyl group. Spectral analysis by 13C, 1H NMR, FT-IR and Mass Spectroscopy confirmed their chemical structures as the following compounds: 2-isopropy1-5-methylphenylformate (1), 2-isopropyl-5-methylphenyl benzoate (2), 5-methyl-2-propylphenyl acetate (3), 2-(2-(2-isopropyl-5-methylphenoxy)ethoxy) ethanol (4) and 2-isopropoxy-1-isopropyl-4-methylbenzene (5). Their antibacterial activity compared to Thymol was assessed by a standard broth microdilution method against five referenced bacterial strains: Escherichia coli a CIP 54127, Salmonella typhimurium an ATCC 133115, Staphylococcus aureus a CIP 4.83, Pseudomonas aeruginosa ATCC 15442 and Klebsiella pneumonia a CIP 104216. Obtained results confirmed enhancement of antibacterial activity of product (5) and moderately of product (3), while products 1, 2 and 4 exhibited low activity comparing to Thymol. These results suggest that the phenolic hydroxyl group of Thymol is involved in the interactions with bacterial structures leading to inhibition of their growth and even killing them at higher doses.