Objective: This study evaluated the anti-amoebic, anti-virulence, and cytotoxic effects of pterostilbene (PS), alone and combined with metronidazole (MZ), against Entamoeba histolytica trophozoites.
Materials and Methods: Trophozoite viability was quantified using the WST-1 assay, and synergistic interactions between agents were assessed via the fractional inhibitory concentration index (FICI). Cytotoxicity was evaluated in FHC intestinal epithelial cells, with selectivity indices calculated. Intracellular reactive oxygen species (ROS) generation was measured using the DCFH-DA assay, and qPCR analyzed expression of key virulence genes (EhCP1, EhCP5, and hgl). Trophozoite adhesion capacity was also examined.
Results: PS significantly reduced trophozoite viability dose-dependently, with IC50 values of 37.1 µM for PS, 28.6 µM for MZ, and 12.7 µM for the combination. A pronounced synergistic effect was observed, with FICI ranging from 0.342 to 0.444. Selectivity indices were 10.71 for PS, 10.18 for MZ, and 14.14 for the combination. ROS levels rose 1.79-fold with PS and 3.62-fold with combination therapy. Virulence gene expression was significantly downregulated, particularly in the combination group, with relative levels of 0.21 (EhCP1), 0.16 (EhCP5), and 0.19 (hgl). Adhesion decreased significantly to 44.6% and 22.7% with PS alone and the combination, respectively.
Conclusion: PS exhibits anti-amoebic activity against E. histolytica and enhances MZ efficacy under experimental conditions. These effects were associated with increased intracellular ROS, reduced expression of virulence-related genes, and impaired parasite adhesion. Although altered redox homeostasis may contribute to these effects, further in vivo and mechanistic studies are required to confirm PS therapeutic potential.