Effect of Solvent Polarity on the Antioxidant Interactions of γ-Tocopherol, β-Sitosterol, and Ellagic Acid in Iron Walnut Oil

This study investigates the antioxidant interactions of γ-tocopherol, β-sitosterol, and ellagic acid in iron walnut oil within ethanol and ethyl acetate, assessing their impact on oxidative stability. In ethanol, γ-tocopherol and ellagic acid display initial synergistic effects, enhancing free radical scavenging beyond their individual capabilities. Conversely, γ-tocopherol and β-sitosterol show antagonistic effects, reducing their combined scavenging abilities. Kinetic analysis indicates ellagic acid's robust scavenging, generally outperforming combinations of antioxidants. Fourier-transform infrared spectroscopy revealed that solvent polarity significantly impacts hydrogen bonding interactions. Ethanol, with its higher polarity, promoted more extensive hydrogen bonding compared to ethyl acetate, which imposed constraints on such interactions due to its lower polarity. Notably, despite its poor solubility in ethyl acetate, ellagic acid exhibits enhanced synergy with γ-tocopherol, likely via electron transfer. These findings underscore the intricate dynamics of antioxidant interactions, further emphasizing the pivotal role of solvent polarity in modulating these interactions. These results indicated that solvent properties significantly influence antioxidant behavior, yet they also introduce novel insights specific to the iron walnut oil system.