With this study, we want to connect experimental and theoretical results of antioxidant activity in soft drinks and determine their correlation. We will determine the antioxidant activity experimentally in soft drinks to which lignans with DPPH (2,2-diphenyl-1-picrylhydrazyl) have been added in certain concentrations and compare it with quercetin and vitamin E. We will connect the antioxidant activity of the compounds with the structures and structural parameters that will be calculated at the semi-empirical level of PM6 and PM7, and if necessary also at the DFT (density functional theory) level, and their dependence will be determined for several compounds using statistical procedures. Then we will focus on the redox properties, and in particular on the transfer of hydrogen to the free radical that arises in a state of oxidative stress in the cell. We will compare quantum-chemical calculations with the structures of compounds, and investigate and propose possible mechanisms of action. We expect that the proposed research will result in useful knowledge, which could serve nutritionists and doctors in the creation of products enriched with lignans.