Tart Cherry (Prunus cerasus) Extract Exerts High Intracellular ROS Scavenging Activity and Repression of ARE (Antioxidant Response Element) Pathway in Human Hepatocytes

Polyphenol-rich fruits represent promising natural candidates for mitigating oxidative stress. We determined in dose-response manner the intracellular antioxidant activities of <i>P. cerasus</i> (tart cherry) extract in HepG2 cells using three different cellular assays targeting specific mechanisms of action: (1) the AOP1 assay, to assess intracellular ROS scavenging activity; (2) the CAA assay, to estimate ROS scavenging activity at the cell membrane; and (3), the HepG2-ARE-luc assay, to evaluate Antioxidant Response Element (ARE) pathway modulation. Tart cherry extract exhibited a high and concentration-dependent intracellular ROS scavenging activity with the AOP1 assay (EC₅₀ of 72.02 µg/mL), whereas antioxidant efficacy measured via the CAA assay was much lower (EC₅₀ of 6.975 mg/mL). Notably, <i>P. cerasus</i> extract did not activate the ARE-driven luciferase gene expression. Instead, the extract induced a clear dose-dependent repression of ARE-driven transcriptional activity, with a reduction in luciferase gene expression ranging from 20 to 70% across the sample tested concentrations (0.38-98 µg/mL). These findings suggest that, at concentrations where it functions as a potent intracellular ROS scavenger, <i>P. cerasus</i> extract exerts a negative regulation of the ARE pathway. Further investigations are warranted to elucidate the compounds underlying these effects.