<p>This study evaluates the antioxidant and gastroprotective properties of hazelnut extracts in a rat model of indomethacin-induced gastric ulcers. The investigation focused on the potential therapeutic effects of different hazelnut extracts, specifically the methanol extract of Trabzon hazelnut, which exhibited the highest antioxidant activity (86.0% inhibition of lipid peroxidation) and phenolic content (significantly higher gallic acid equivalents). The extracts demonstrated significant gastroprotective effects by reducing ulcerated areas in rat gastric tissues induced by indomethacin, with the methanol extract of Trabzon hazelnut showing a 90.6% reduction in ulcer index at a dose of 100&#xa0;mg/kg. Additionally, the extracts enhanced the antioxidant defence system by increasing catalase activity to 19.02 mmol/min/mg tissue, reducing lipid peroxidation levels to 52.67 nmol/g tissue, and restoring glutathione levels to 2.10 nmol/g tissue. These findings underscore the potential of hazelnut extracts as natural antioxidants and gastroprotective agents, highlighting their promise in mitigating oxidative stress and preventing chronic diseases. This analysis of multiple biochemical parameters, with a focus on both antioxidant and gastroprotective effects, provides a foundation for future research. Further research is recommended to explore the mechanisms underlying these effects, conduct clinical trials, and investigate potential food applications to expand the understanding of the antioxidant and gastroprotective properties of hazelnuts.</p>