Solvent-Driven Variation in the Determination of Antioxidant Capacity and Oxidative Stress Indicators of Extra Virgin Olive Oils from the Aegean Region

This study investigated the influence of different extraction solvents (ethanol and methanol) on antioxidant and oxidative stress parameters in 55 extra virgin olive oil samples obtained from various producers in the Aegean region of Türkiye. In this context, DPPH radical scavenging activity, total phenolic content (TPC), total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) were determined in both extracts. Ethanol extracts showed higher TPC and DPPH radical scavenging activity, with mean DPPH values of 24.48% and 15.42% for ethanol and methanol extracts, respectively. Similarly, TOS and OSI values were higher in ethanol extracts, whereas TAS values were higher in methanol extracts. Correlation analysis revealed significant negative relationships between antioxidant parameters (TPC and TAS) and OSI, indicating an inverse association between antioxidant capacity and oxidative stress. Principal component analysis (PCA) demonstrated a distinct separation between antioxidant and oxidant variables. Bland–Altman analysis further confirmed systematic differences between extraction methods. Overall, the findings indicate that the extraction solvent is a critical factor in the determination of antioxidant and oxidative stress parameters in olive oil. Ethanol provides a higher phenolic content and radical scavenging activity, whereas methanol appears more effective in assessing total antioxidant capacity. The variability among samples reflects differences in production, processing, and storage conditions.