Anti-Amoebic Activity of Eugenol Derivatives against Acanthamoeba castellanii

Eugenol is the major compound of clove and has demonstrated various pharmacological activities. In this study, nine eugenol derivatives (1-9) were synthesized, characterized, and further evaluated for their anti-amoebic properties against Acanthamoeba castellanii (A. castellanii) trophozoites. The derivatives were obtained through etherification or esterification reaction at the hydroxyl group (-OH) of eugenol. The chemical structures of the synthesized derivatives were characterized on the basis of 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. For anti-amoebic activity, the cytotoxicity of the derivatives was tested on A. castellanii trophozoites. The samples were prepared at varying concentrations (in the range of 0.47 to 60 μg/mL). The IC50 values were examined based on MTT assay while light and fluorescence microscopy were used to visualize the morphology changes of amoeba in detail. The results obtained were compared with the standard drug, which was chlorhexidine. Several of the tested derivatives possessed cytotoxic effects against throphozoite cells with IC50 in the range of 0.58 to 27.83 μg/mL with significant decrease (p < 0.05) in cell viability as the concentration was increased up to 30 μg/mL. Among them, derivative 4 provided the strongest cytotoxic effect against A. castellanii, suggesting a promising new anti-amoebic agent. Altogether, this finding may potentially serve as the milestone for developing an alternative treatment for Acanthamoeba keratitis.