Electrochemical Oxidation Property of Antioxidative Substances in the Oil-Based Solution

Antioxidative substances constitute the important barrier maintaining the oxidative stability of edible oils against lipid degradation and the formation of harmful aldehydes and ketones. In this study, an oil-compatible non-aqueous electrochemical method was developed to characterize the oxidation behaviour of antioxidative substances in an oil-based solution, in which linear sweep voltammetry (LSV) was employed to investigate the effects of oxidation potential and current on antioxidative capabilities of eleven antioxidative substances, including both natural and synthetic compounds, in a mixed anhydrous model oil system. Among them, eight antioxidative substances exhibited characteristic oxidation peaks in the mixed solution containing 0.1 mol/L Lithium perchlorate, 40% (v/v) C8 medium-chain triglyceride, 35% anhydrous ethanol and 25% 1,2-dichloroethane, with the first oxidation peak potentials (vs. Ag/AgCl) increasing in the order: TBHQ (100-800 mg/kg, (-247)-(-119) mV), PG (100-800 mg/kg, 74-248 mV), α-tocopherol (100-800 mg/kg, 95-142 mV), δ-tocopherol (100-850 mg/kg, 190-241 mV), BHT (100-800 mg/kg, 238-256 mV), β-carotene (100-870 mg/kg, 562-624 mV), lutein (100-850 mg/kg, 631-680 mV) and ergosterol (100-850 mg/kg, 1240-1300 mV), while their peak potentials were negatively correlated with the DPPH and Galvinoxyl radical-scavenging capacity, suggesting that, under the present oil-based conditions, lower oxidation peak potentials tended to be associated with stronger radical-scavenging capacity. The concentration-current relationships were compound-dependent and followed linear, cubic, or logarithmic patterns. And the oxidation of phenolic antioxidative substances shifted from a low-potential to a higher-potential process under acidic conditions. Overall, this study reveals the electrochemical oxidation properties of antioxidative substances in the oil-based solution, and provides the electrochemical characteristic method of the antioxidant capacities of antioxidative substances and application guidance for antioxidative substances screening in oil.