Decoding Tocopherol–Polyphenol interactions in oil-in-water emulsions through combined WIM-CAT and CV assays

The antioxidant interactions of α- and γ-tocopherol with curcumin and quercetin were assessed in an oil-in-water emulsion using the WIM-CAT assay, a method integrating Weibull interaction modeling with the conjugated autoxidizable triene technique. Synergistic effects were strongest for γ-tocopherol with curcumin and for α-tocopherol with quercetin, particularly at low tocopherol concentrations (0.2 μM in emulsion, 380 ppm in oil) and high molar ratios (3:1). Increasing tocopherol concentration to 0.6 μM in emulsion (1140 ppm in oil) reduced synergy, likely reflecting pro-oxidant activity. The presence of ferrous ions accelerated oxidation but did not influence synergistic interactions, while acidic conditions reduced tocopherol pro-oxidation and modified the effects of curcumin and quercetin. Weibull modeling revealed isoform-dependent differences during the propagation phase of oxidation. Cyclic voltammetry further suggested that the synergy of α-tocopherol may involve antioxidant regeneration mechanisms, whereas γ-tocopherol appears to act through alternative redox processes. Together, kinetic and electrochemical analyses provide complementary insights into the conditions governing antioxidant interactions. • WIM-CAT and voltammetry reveal isoform-specific antioxidant synergy in emulsions. • γ-Tocopherol–curcumin and α-tocopherol–quercetin show highest synergy at low TOH. • High tocopherol levels induce pro-oxidant effects and reduce antioxidant synergy. • Weibull modeling distinguishes polyphenol effects on initiation and propagation. • pH and Fe 2+ strongly modulate antioxidant efficiency in PUFA-rich emulsions.