Abstract (PDF) Graphical Abstract: The study presents data on the antioxidant interaction between ascorbic and dihydroxyfumaric acids determined via DPPH method, by applying EPR spectroscopy. The type of antioxidant interaction is dependent on the concentration ratio of the ascorbic and dihydroxyfumaric acids, thus, at the mM DHF/mM AA ratios of 1.4 and 1.7 the highest synergistic effects of 1.24 have been noticed, but at the mM DHF/mM AA ratio of 1 – an antagonistic effect of 0.93 was registered.