Investigation of antioxidant synergisms and antagonisms among thymol, carvacrol, thymoquinone and p-cymene in a model system using the Briggs–Rauscher oscillating reaction

Auto-oxidation of lipids has been recognised as a major deterioration process affecting both the sensory and nutritional quality of foods; the application of antioxidants is one of the technically simplest ways of reducing this process. Previous reports showed that these compounds were found in selected aromatic plants and that thymol, carvacrol, thymoquinone and p-cymene as constituents of different essential oils possess substantial antioxidant activity. In the present study their antioxidant capacities were evaluated using the Briggs–Rauscher oscillating reaction method. sults indicate that the majority of the antioxidant mixtures demonstrated some level of discrepancy in antioxidant capacity when compared to individual values of their constituents. The strong antagonistic effect was found only when thymoquinone was paired with p-cymene. All other combinations of two antioxidants clearly showed some degree of synergistic effect. The mixtures of three antioxidants showed a decrease in antioxidant capacity when compared to their individual values. The results obtained for more complex mixtures of four antioxidants showed a decrease in antioxidant capacity, indicating and confirming that the antagonistic effect between thymoquinone and p-cymene overrides the synergistic effect of other pairs.