This study compares the antioxidant capacities in vitro of several synthetic and natural compounds applied and researched for influenza treatment – oseltamivir, isoprinosine, ellagic acid, vitamin E and vitamin C. Three chemical systems are utilized for the generation of reactive oxygen species (ROS) at pH 7.4 and pH 8.5: (1) Fenton’s (Fe²⁺+H₂O₂) for OH and −OH species (2) H₂O₂ (3) NADH-phenazinemethosulfat, for superoxide radicals (O₂⁻).

The kinetics was evaluated by lucigenin-enhanced chemiluminescence. The calculated constants of inhibition k₇ describe the antioxidant capacity at the moment of oxidative burst. Their values do not necessarily correspond to the calculated total antioxidant activity.

The obtained results revealed that the synthetic anti-influenza drugs (oseltamivir and isoprinosine) as well as ellagic acid possess pronounced scavenging properties mostly against superoxide radicals, comparable and higher than that of traditional natural antioxidants. Quantitative analysis of the antioxidant effects of the examined synthetic substances was performed. The results compared the corresponding effect of the average physiological concentrations and the applied therapeutic antioxidant dose. With these experiments we registered new aspects of their therapeutic activities, due to antioxidant properties against hydroxyl, superoxide radicals and H₂O₂ oxidation.