Abstract:
Eugenol possesses various biological activities, including anti-inflammatory, antimicrobial, antidiabetic, anticancer, etc. The purpose of synthesising new eugenol derivatives in this study was to determine whether they possess greater antibacterial activity than eugenol without the presence of the toxic phenol group characteristic of eugenol. Thus, the main objective of this research is to synthesise and test the antibacterial activity of the new eugenol derivatives on four bacterial strains.
Eugenol dissolved in sodium hydroxide solution was added with acid chloride and stirred for 4 hours at room temperature. A total of 6 eugenol derivatives were synthesised using various methods, and the synthesis methods were optimised accordingly. The compounds were characterised using 1H and 13C NMR spectroscopy, FTIR spectroscopy and UV-Visible spectroscopy. The antibacterial activity of the synthesised compounds was evaluated using disk diffusion and resazurin assays. Four representative bacteria (2 gram-positive and 2 gram-negative) were selected to assess the antibacterial activity of the synthesised compounds. Additionally, in silico study was done to predict the drug-like properties of eugenol and its derivatives using the Schrödinger Small Molecule Drug Discovery Suite.
The target compounds were produced and characterised using spectroscopic techniques. Few target compounds showed moderate antibacterial activity on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA), with the most prominent compound being EU1e showing bactericidal effect against E. coli. Overall, eugenol possesses a broader antibacterial effect compared to the synthesised compounds, as it exhibited activity on all strains of the bacteria. The in-silico study predicted that most compounds had good oral bioavailability. However, besides compound EU2a and EU2b, all other derivatives were potentially cardiotoxic.
In conclusion, this study successfully showed the antibacterial effect of most eugenol derivatives on different strains of bacteria, especially compound EU1e, against E. coli. Essentially, eugenol still had greater antibacterial activity than the rest of the synthesised derivatives.
