Synthesis of 1,2,3-triazole-thymol derivatives as potential antimicrobial agents

Thymol as a natural biological template can be modified chemically since the hydroxyl group makes it a candidate for structural modification. Thus, this study incorporated the triazole moiety on thymol and the chlorination of thymol moiety to help improve its biological potency. Materials and

These results provide additional evidence of the exploitation of natural products like thymol as leads for drug development against medically important bacterial pathogens.

A series of ten 1,2,3-triazole-thymol derivatives 1-10 were synthesized from thymol, by a click reaction between O-propargyl terminal alkyne of thymol and its chlorothymol with benzyl azide and substituted benzyl azides. Their structures were confirmed by spectroscopic methods (1H-NMR, 13C-NMR, IR, GC-MS-EI/CI and LC-ESI-QTOF-MS). The Well diffusion method using Müeller-Hinton agar plates was used to demonstrate the antimicrobial activities of the synthesized triazole-thymol derivatives on selected bacterial strains; Escherichia coli ATCC 25922, Staphylococcus aureus ATCC25923, Methicillin resistant S. aureus (MRSA), Pseudomonas aeruginosa ATCC 29853, E. coli ESBL, K l ebsiella pneumoniae NCTC 13438 and Meropenem Resistant E. coli.

All the synthesized triazole-thymol derivatives showed significant but variable antibacterial activity against the seven medically important bacterial strains tested. The compound 4-((4-chloro-2-isopropyl-5-methylphenoxy)methyl)-1-(2-nitrobenzyl)-1H-1,2,3triazole (9) demonstrated a higher antibacterial activity with a mean zone of inhibition (38.7 mm) compared with ampicillin as the positive control which gave a zone size of 30.0 mm. In addition, the compound showed a three-fold potency than the parent compound, thymol (11.0 mm) against MRSA at a concentration of 100 μg/ml.