With the growing emergence of antibiotic resistance in bacteria, exploration for new antimicrobial agents is essential. Essential oils are secondary metabolites of spices, aromatic herbs, and flowers. Many of these compounds are terpenes that display antimicrobial properties. The monoterpene menthol has moderate antimicrobial effect against both gram-negative and gram-positive bacteria. Menthol was derivatized via chlorination, oxidation, and acylation. These derivatives were purified and characterized with IR spectroscopy, NMR, and GC-MS. Bacterial broth cultures of E. coli, B. subtilis, S. aureus, and P. aeruginosa were incubated for three days in Lysogeny broth medium. To determine the minimum inhibitory concentration (MIC), a serial dilution of broth culture was conducted and tested against increasingly dilute derivative compounds. Each broth dilution was quantified separately for colony forming units (CFU) to standardize the MIC procedure. Prior to incubation, cotton disks infused with MIC levels of derivatized compounds, menthol (for control), and penicillin were placed on the agar surface. These plates were incubated for three days before the zone of inhibition was recorded. At the MIC, all derivatives and menthol showed similar or smaller zones of inhibition compared to the control antibiotic, penicillin.

Antimicrobial properties of menthol and its derivatives

2019 Spring National Meeting

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